Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Title: Micro Molecules
Description: These notes give an overview about the structure of micro molecules. These notes are suitable for High school and undergraduate students
Description: These notes give an overview about the structure of micro molecules. These notes are suitable for High school and undergraduate students
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
I CHEMICALS OF LIFE
Cells, tissues and organs of plants and animals are made up of chemicals
...
The study of chemical compound found in living things and the reactions in
which they take part is called biochemistry
...
Chemical compounds are made up of the following elements and ions
• Chief elements of organic molecules such as; C, H, O, N, P, S
...
g
...
The four most important elements in living organism are CHON
...
the biological
importance of these elements is that they have valencies 1, 2, 3, and 4 respectively which
enable them form more stable covalent bond than other elements of the same valencies
...
a
...
these are complex compounds of carbon
...
carbon
is very essential to life because it has some important chemical properties
•
it is a relatively small molecule with a low mass
•
it has the ability to form four strong covalent bonds with other elements e
...
methane
CH4
...
g
...
•
has the ability to form multiple covalent bonds with other carbon atoms, O, and N
the main organic compounds found in living organisms are
...
1
b
...
the most important inorganic compounds found in living things
are water, acid and bases
Biological molecules
...
some molecules exist as
simple molecules such as CO2, H2O while others as macromolecules e
...
protein
...
large molecules are used for storage e
...
starch, glycogen etc
...
g
...
a
...
This is the most abundant molecule in living organisms and constitute 60 to 95% of fresh
mass
...
without water life on earth is
impossible
...
It is
made up of hydrogen and oxygen in the ratio 2:1 and one of the rare substances to exist in the
natural environment in three physical states of matter: solid, liquid, and gas
...
These properties are rather unusual due to the small size of the water molecule, its
polarity and hydrogen bonding between its molecules
...
one part is partially negative while the other is partially
positive and this is called dipole
...
the individual molecules when grouped
together attract each other forming a weak bond called hydrogen bond
...
diagram
...
Water is an excellent solvent for all polar substances such as salt and sugar whose ions and
polar groups dissociate easily in contact with water
...
this
property also helps it to act as a transport medium as in blood, xylem, phloem, alimentary
canal, excretory system etc
...
e
...
they usually group together in the presence of water
...
it also helps to
determine the three dimensional figure of many protein molecules, nucleic acid and other cell
structure
...
This is the heat needed to raise the temperature of 1kg of water by 1 degree centigrade
...
this high heat capacity help to keep the temperature of water in living organisms
constant favouring biochemical reactions which takes place within narrow temperature range
...
water has a remarkable high
boiling point for such a small molecule
...
•
High heat of fusion
...
Ice need relatively large amount of heat to
change from solid to liquid, on the other hand liquid water need to loss a relatively large
amount of heat in other to freeze
...
•
Density and freezing property
...
It is the only substance whose solid form is less dense and has a large volume than its
liquid form
...
This enable aquatic organisms to survive and are
protected at the bottom of ponds during winter
...
•
High surface tension, cohesion and adhesion
Water molecules stay close to each other as a result of hydrogen bonding
...
3
Cohesion due to hydrogen bonding contributes to the transport of water and dissolved
nutrients against gravity in xylems of plants
...
Adhesion (the clinging of one substance to another) of water to cell walls by hydrogen bonds
helps counter the downward pull of gravity
...
Water has a greater surface tension than most other liquids
...
This allows the movement of some organisms like the
pond skaters on water
...
Even a slight change in pH can be harmful,
because the chemical processes of the cell are very sensitive to the concentrations of
hydrogen and hydroxide ions
...
There are several buffers that contribute to pH stability in human blood and many other
biological solutions
...
Carbonic acid dissociates to yield a bicarbonate ion (HC03-) and a
hydrogen ion (H+):
4
The chemical equilibrium between carbonic acid and bicarbonate acts as a pH regulator
...
But when H+
concentration in blood begins to rise (when pH drops), the reaction proceeds to the left, with
HC03- (the base) removing the hydrogen ions from the solution and forming H2C03
...
With references to living systems, living organisms or processes in living organisms, explain
how the following properties of water have contributed to the development of life on earth
...
Draw the diagram of the water cycle and explain:
•
Processes that carry water to the atmosphere
•
Processes that return water to the earth surface
•
Processes through which water circulates among living organisms
•
what are the biological functions of water?
Macro molecules
...
They are called polymers while the individual
small molecules or units are called monomers
...
Macromolecules are broken to give
monomers by the addition of water (hydrolysis)
...
polysaccharides are used for food storage or structural purposes while proteins and nucleic
5
acid are regarded as informational molecules
...
Carbohydrates
...
they are called
hydrate of carbon because H and O occur in the same proportion as in water
...
their chemistry is determined by
these groups
...
Carbohydrates are divided into two
main classes, sugars and polysaccharides
...
e
...
Have the following
characteristics
•
They are small molecules
•
They are sweet
•
They are readily soluble in water
•
They are crystalline
•
their names always end in ose e
...
glucose, sucrose
...
Monosaccharides
...
Their general formula is (CH2O)2 where n=3 to 9
...
all
monosaccharides are reducing sugars
...
In monosaccharides, one of its C atom is do not
have the OH group attached to it
...
when it is part of an aldehyde group the monosaccharide is called an aldose or aldo
sugar e
...
glucose, ribose, glyderaldehyde
...
g
...
diagram
...
pentose and hexose usually exist as rings
with only a small proportion in open chain form at any given time
...
In pentoses the first carbon atom joins
with the Oxygen atom on the fourth carbon atom, while in the hexoses, like glucose carbon 1
joins with the Oxygen atom of carbon 5 to give a six membered ring
...
Diagram
...
When the hydroxyl
group on carbon atom 1 project below the ring we have alpha glucose while when it projects
below the ring we have beta glucose
...
in a glucose solution, some
molecules will be in open chain form while some in the ring form
...
Diagram
...
They are broken down
during cellular respiration to release energy
...
Sugar molecules that are not immediately used for the production of energy or other small
organic molecules are incorporated as monomers into disaccharides or polysaccharides
...
They are formed when two monosaccharides such as hexoses combine by means of a
chemical reaction called condensation
...
(condensation, hydrolysis)
The bond between the monosaccharides is called glycosidic bond and is formed between
carbon atom 1 and 4
...
the
monosaccharides units are called residues once they have been linked
...
some disaccharides are reducing sugar while others are not
...
it is formed from two alpha glucose molecules
...
maltose in
germinating seeds is made use of in brewing beer
...
Sucrose
...
it is formed from a glucose and a fructose molecule
...
sugar cane and sugar beet are the main sources of sucrose for commercial sugar
...
Lactose
...
it is digested slowly thus gives a slow steady release of energy
...
it is also a reducing sugar
Reducing sugar
...
the reducing
property of these sugars can be tested using Benedicts or Fehlings solution
...
ie Cu is reduced from a valency of 2 to 1
...
All monosaccharides and some disaccharides like maltose and lactose are reducing sugar
...
Polysaccharides
...
the condensation process is repeated several times to build up giant molecules
...
their general formula is (C6H10O5)n where
n= number of monosaccharides
...
•
Are macromolecules
•
Are not sweet
•
Are insoluble or slightly soluble in water
•
They are non-crystalline
...
g
...
They are easily converted to sugar by
hydrolysis when required
...
g
...
Starch
...
in plants, it forms a helices and act a storage compound
which on hydrolysis gives a monosaccharide such as glucose for respiration
...
starch is absent in animals
...
Amylose
...
these chains do not usually remain straight but also coils helically into a
more compacted structure
...
it is usually longer than amylose and has about twice as many glucose
molecules as amylose
...
diagram
...
this forms the bases of the
test for starch
...
put 2cm3 of starch suspension into a test tube and add 2drops of iodine or KI solution
observation
...
conclusion
...
Functions of carbohydrates
...
g
...
g
...
g
...
g
...
g
...
g
...
•
strengthening material in the cell wall of bacteria e
...
murein
Glycogen
...
It is similar
to amylopectin but more extensively branched
...
Hydrolysis of glycogen in these cells releases glucose when
the demand for sugar increases
...
Cellulose is a
polymer of β-glucose and the most abundant organic compound in nature
...
LIPIDS
...
they are non-polar and
contain the elements CHO
...
they are
formed by condensation reaction between fatty acids and alcohol i
...
glycerol+ fatty
acid=lipid thus fatty acid and glycerol are subunit of lipids
...
the difference between fats and oil is that at room temperature fats
are solids while oils are liquids
...
11
Constituent of lipids
...
•
They contain the acid group (COOH)
•
have the general formula R-COOH where R is hydrogen or group such as CH3, C2H5
etc
...
there are two types of fatty acids
...
Saturated fatty acids
...
g
...
•
lipds containing them are said to be saturated e
...
fats like butter
...
Unsaturated fatty acids
...
g
...
b
...
12
Most lipids are formed from alcohols called glycerol
...
diagram
...
The 3-OH groups of glycerol each react with fatty acid
...
the lipid form is triglyceride such as tristearin
...
they are either fats or oils depending on the amount of saturated or unsaturated fatty acids
they contain
...
•
lipids are insoluble in water but soluble in organic solvent such as ether
•
the tail of lipids is hydrophobic (water hating) and the heads are hydrophilic (water
loving)
Types of lipids
...
Phospholipids
...
they are formes when
2-OH groups of glycerol combine with 2 fatty acids and the last one with a
phosphoric acid
...
thus one end of the molecule is soluble while the other end insoluble
...
diagram
...
Glycolipids
...
carbohydrates form polar
head of the molecule and they are also found in membranes
...
Steroids
13
Steroids are lipids characterized by a carbon skeleton consisting of four fused rings
...
Different steroids vary in the chemical groups attached to this ensemble of rings
...
Many hormones, including vertebrate sex
hormones, are steroids produced from cholesterol
...
what are the differences between polysaccharides and phospholipids?
Functions of lipids
...
14
•
insulate the body from cold that is excess fat stored under the skin of animals during
hibernation which help to prevent them from cold
...
•
used in the formation of the cell membrane e
...
glycolipid and phospholipids
•
help in the protection of vital organs in the body such as the kidneys, and the heart
...
•
help in buoyancy of aquatic vertebrates like shakes and whales because it is less dense
than air
...
the skin of
animals like man produces oily secretion from the sebaceous gland which makes it
water proof
•
help in the formation of waxes
•
break down of fats produces water which is useful to desert animals such as the
kangaroo rat
...
bees
use wax in constructed their honeycomb
...
This subcutaneous layer is
especially thick in whales, seals, and most other marine mammals, protecting them
from cold ocean water
...
A diet rich in saturated fats is one of several factors that may contribute to the
cardiovascular disease known as atherosclerphotosynthesis
...
What is the role of lipids in the structure of cells?
Test for lipids
...
they complex organic compounds which contain the elements CHON and in some cases
Sulphur
...
they are the most abundant organic molecules in cells and form over
50% of total dry mass
...
the basic units or monomers of proteins are amino acids
...
based on structure, proteins are classified into two main groups that is fibrous and globular
proteins
...
they are tough, insoluble and consist of long parallel polypeptide chains,
cross-linked at intervals forming long fibres or sheets
...
g
...
globular proteins
...
e
...
enzymes, antibodies and hormones
...
Amino acids
...
out of the 170 amino acids that exist, only 20 are found in
proteins
...
some exist in the body but do not
enter into the composition of protein like GABA (gama amino butyric acid, inhibitory
neurotransmitter) found in the nervous system
...
structure of amino acid
...
the 4th position is occupied by a variable group represented by R group which gives
each amino acid it uniqueness
...
the simplest amino acid is glycine where R=H
...
diagram
...
•
amino acids are soluble in water but insoluble in organic solvent such as ether
...
•
they are dipolar and are called zwitterions that is exist as ions with +ve charge on the
NH2 group and _ve charge on the COOH group
...
zwitterion is neutral thus pH at which this neutrality is created is called isoeletric
point
...
they donate H+ when pH increases and accept
H+ when pH decreases
...
even H2O can be considered amphoteric
...
At one end of the polypeptide chain is a free amino group; at the opposite end is a free
carboxyl group
...
The repeating sequence atoms is called the polypeptide backbone
...
Each specific polypeptide has a unique linear sequence of amino acids
...
they have three dimensional shape called its conformation
...
the polypeptide chain
generally folds spontaneously, assuming the functional structure
...
Many proteins are roughly spherical (globular proteins), while others are shaped like long
fibres (fibrous proteins) or globular and tightly bounding non protein material (conjugate
protein)
...
The function of a protein depends on
its ability to recognize and bind to some other molecule
...
Linear sequence of amino acids in a polypeptide chain
...
Diagram
...
A mutation which causes one of the hydrophilic amino acids to be replaced by a
hydrophobic amino acid, thus reducing its solubility causes sickle cell anaemia
...
Thus slight change in primary structure can affect a protein's shape and ability to
function
...
There are two types i
...
alpha helix and beta pleated sheet
...
An alpha helix is a twisted strand while beta pleated sheet is a zig-zag lines of amino
acids bound to the next
...
while fibroin is a protein which is entirely beta pleated sheet such as milk
...
Tertiary structure
...
The polypeptide is held in bends and tucks in a permanent shape by a range of bonds
such as disulphide bridges(s-s), H-bonds, ionic bonds, and hydrophobic interactions
...
Diagram
...
19
Some proteins are made up of different polypeptides bonded together to form an extremely
intricate shapes
...
The separate chains are held by hydrophobic interactions, H-bonds and ionic bonds
...
What are the types of bonds found in protein structure (list and explain)?
•
peptide bond
...
what are the common structural features between triglycerides, phospholipids and
glycolipids?
Types of protein based on functions
...
Structural protein
...
e
...
collagen, keratin, elastin, viral coat protein
...
Enzymes
...
3
...
•
Insulin and glucagon help to re
...
ulate glucose metabolism
•
ACTH (adrenocorticotrophic hormon) stimulate growth and activity of the adrenal
cortex
4
...
Haemoglobin transport oxygen in vertebrates while myoglobin store oxygen in muscles
...
Protective protein
...
6
...
Serum albumin transport fatty acids and lipids in blood
7
...
albumin (e
...
g white) myoglobin (stores oxygen in muscles) and casein
in milk
...
carry messages around the body e
...
insulin that control blood glucose level
...
Buffers proteins
...
9
...
membrane proteins transport substances across the cell membrane during processes like
facilitated diffusion
11
...
Conjugate proteins
...
the non-protein material is called a prothestic group
...
protein
prothestic group
location
phosphoprotein
phosphoric acid
casin of milk, vitelin of e
...
g yolk
glycoprotein
carbohydrate
membrane structure, mucin of saliva
...
dinucleotide)
Test for proteins
...
procedure
...
g
...
g
...
•
add 1cm3 of millon’s reagent and boil
...
observation
...
conclusion
...
thus food sample contain proteins
...
procedure
...
g
...
•
add two drops of 1% CuSO4 solution and mix by shaking
...
observation
...
conclusion
...
Denaturation of proteins
...
Though
the amino acid sequence remains the same, the protein can no longer perform its normal
biological function
...
This usually breaks the
bond that hold the secondary, tertiary and quaternary structure
...
There are a number of agents that denatures proteins as follows
...
•
Strong acid and alkalis and salts of high concentration
•
Heavy metals
•
Organic solvents and detergents
Renaturation of protein
...
it is the spontaneous refolding of
protein into its original structure provided conditions are suitable
...
Chemicals
Some chemicals disrupt the hydrogen bonds, ionic bonds, and disulphide bridges that
maintain a protein's shape
...
g
...
Heat
Excessive heat agitates the polypeptide chain and breaks the weak interactions that stabilize
the structure
...
pH
23
pH affects the ionisation of side groups necessary in the establishment of ionic interactions
and H-bonds
...
They are organic compounds that constitute the genetic material of all living organisms
...
Nucleic
acids are made up of units called nucleotides
...
There are two types of nucleic acid found in cells that
is RNA and DNA
...
They are easily identified in the nucleus as fine threads which become shorter and thicker
prior to cell division
...
in man there are 23 pairs of chromosomes, 22 pairs are
identical and carry genes that determine other characteristics (non-sex chromosomes) while
the 23rd pair are unidentical and carry genes that determine sex (sex chromosomes)
...
a pair of gene determining a particular
contrasting xter is found in the same locus or point
...
this is the basic unit of inheritance for a given characteristic
...
Evidence that the nucleus contains hereditary material
...
Later experiment carried out by
scientist at the be
...
inning of the of the 20th century show that DNA is the heredity material
...
g
...
Such an
e
...
g usually dies if the nucleus is not return into the cell within a short period of time
...
g
...
a
...
•
Frederick Griffith carried out experiment in 1928 using the bacteria pneumococcus
which exist in two forms
...
and obtain the following results
...
•
he concluded that something must be passing from the heat killed capsulated forms to
live non-capsulated which caused them to develop capsules and become virulent
...
•
The movement of a gene from one organism to another (transformation) provided
some key evidence that DNA is the genetic material
...
Evidence to support the fact that heredity is associated with DNA
...
•
The virus infects and injecting its DNA into E
...
Viral DNA enable formation of viral particles which assemble to form new
viruses in bacterium
...
•
This was demonstrated by Hershey and Chase with the fact that phage DNA
containing phosphorus but not sulphur while protein coat contain sulphur
•
viral DNA IN some T2 phage were labelled with radioactive isotope of 32P while in
others, the viral protein coat was labelled with a radioactive isotope of sulphur (36S)
...
coli and given time to infect the host cell but
not enough time to reproduce
...
coli was infected with T2 phage containing 36S (labelled protein), little
radioactivity occured within the bacteria cells
...
when the bacteria cell burst, new viruses that emerged were radioactive labelled with
32P
...
•
it was concluded that only viral DNA enter the bacteria while protein coat remains
behind
...
structure of nucleic acid
...
two nucleotides join to form dinucleotides
while many join to form a long chain called polynucleotide
...
, a 5 carbon sugar, nitrogenous base and phosphoric acid
...
sugar
...
DNA contain pentose sugar called deoxyribose while
RNA contain contain the pentose sugar ribose
...
nitrogenous bases
...
1
...
they are bases with two ring structure that is adenine (A) and guanine (G) and are found in
both DNA and RNA
...
pyrimidine bases
...
thymine is chemically similar to uracil (diagrams)
c
...
It gives nucleic acid their acid property
...
Formation of nucleotides
...
this combination is first
between a sugar and a base forming a compound called nucleoside through a condensation
reaction
...
two nucleotides then join to form dinucleotide by condensation
between the phosphate group and the process is repeated several times to form
polynucleotide
...
(diagrams)
...
•
According to Watson and Crick model (1953), the DNA molecule is made up of a
double stranded polynucleotide chain
...
•
the nucleotide consists of pentose sugar (deoxyribose), a phosphate group and four
organic nitrogenous bases (adenine, guanine, cytosine and thymine)
...
•
adenine and guanine are purine bases while thymine and cytosine are pyrimidine
bases
...
•
there are three hydrogen bonds between guanine and cytosine (G…C) and two
between adenine and thymine (A=T)
...
27
•
The two polynucleotide strands are antiparallel meaning that one strands exist in the
5', 3' direction while the other strand exist in the 3', 5' direction
...
•
it has a very high molecular mass, insoluble and a high melting point
...
4nm
with 10 base pairs of nucleotides
...
Structure of RNA (ribonucleic acid)
...
•
has the pentose sugar ribose with smaller molecular mass?
•
organic nitrogenous bases present are 2 purine bases; Adenine (A), Guanine (G) and 2
pyrimidine bases; Cytosine (C) and Uracil (U)
...
•
soluble and chemically less stable
•
there are three forms namely messenger, transfer and ribosomal RNA
...
during its
formation only one strand of DNA molecule is copied
...
most exist in the cell for a short while
...
Ribosomal RNA (rRNA)
...
g
...
base sequence in rRNA is similar in all organisms from bacteria to
higher plants and animals
...
ribosomes are the sites of protein synthesis
...
Transfer RNA (tRNA)
...
its main function is to carry amino acid to ribosomes where
they are linked together during protein synthesis
...
it
forms three main loops
...
the base sequence of the rest of the molecule is variable and may include some
unusual bases such as inosine (I) and pseudouracil (Y)
...
the arm is thus called the amino acid arm
...
...
codon
...
the sequence of codons will determine the sequence of amino acid s
that will produce a particular protein
...
group of three nucleotide bases that are complementary to a codon on mRNA
...
template
...
g
...
the DNA
template refers to the sequence of bases on DNA molecule of a chromosome that will
determine the sequence of complementary bases on RNA molecule to be synthesized
...
•
This is the formation of other DNA molecules from existing DNA molecule
...
this is because
each new double helix formed retains or conserves one of the two strands of the
original DNA double helix
•
During replication the double helix unwinds and is controlled by enzyme helicase
...
•
Each strand then acts as a template (parent) with new bases coming in contact with
their complementary bases to form new strand opposite the parent strand
...
the three
nucleotides then join to form a new strand called the leading strand
...
this is called
continuous replication
...
•
This new strand called Lagging strand is synthesised in small pieces called Okazaki
fragment
...
this is called discontinuous replication
...
diagrams
...
The information for the synthesis of proteins is present in the DNA in a sequence of
nucleotides
...
That gene or fragment of DNA which carries
the code for synthesis of a complete polypeptide (protein) is termed a cistron
...
•
Triplet code
...
E
...
GAC codes for the amino acid aspartic
acid in the polypeptide
...
•
It is de
...
enerate- given amino acid may be coded for by more than one codon
...
g
...
•
It is non-overlapping
...
it is read continuously from be
...
inning to end AUG/AGC/GCA
...
31
•
Puntuated code
...
the start signal is given by AUG which code for amino acid
methionine (met) while the stop signal (nonsense codon) which are usually UAA,
UAG and UGA
...
You can use the mnemonic
PLUTUND to remember the characteristics of a genetic code
...
It reads from a starting point to a finishing point
...
DNA and the Central dogma (DNA is capable of undergoing 1-replication, 2transcription, and 3-translation of genetic information)
The central dogma in gene expression holds that genes are in the nucleus and proteins are
synthesised in the cytoplasm of the cell
...
The central dogma operates in the
following sequence of information flows from DNA (particular gene) to the particular protein
through RNA
...
Messenger RNA carrying
information moves out of nucleus into the cytoplasm, attaches to the ribosomes to translate
the information in the form of a protein
...
Protein synthesis
...
These proteins could be
functional such as enzyme, hormones, antibodies etc
...
in order to produce these proteins, DNA is capable of undergoing transcription
...
the enzyme responsible for
this process is called transcriptase
...
•
Process by which the base sequence of a section of DNA representing a gene is
converted into the complementary base sequence of mRNA
...
only one of these strands of DNA will serve as a template from which mRNA is
produced
...
•
The free nucleotide bases will each pair up with its complementary base that is A-U,
C-G
...
•
The DNA double helix rewind and fold itself to the original stable molecule
•
mRNA then leaves the nucleus through the nuclear pore to the cytoplasm, as
transcription is complete
...
the non-coding portions (introns) of primary mRNA transcript are eliminated while
the coding portions (exons) are spliced together to form the functional mRNA
molecule
...
diagram 802 bs
...
•
Process by which the sequence of bases in a mRNA molecule is converted into a
sequence of amino acids in a polypeptide chain
...
•
Binding of mRNA to ribosomes
...
the first codon is usually AUG and its anticodon on the tRNA carries the
amino acid methionine (met)
...
the amino acid is attached to
the 3' end of the tRNA
...
after the attachment of amino acid to the tRNA, aminoacyl-tRNA
complex is formed
...
the codon AUG is complementary to UAG which
carries the first amino acid methionine and this is the start signal or polypeptide chain
initiation
...
the rRNA has a large and a small unit and it moves along mRNA
in the direction of 5', 3'
...
once the peptide is formed, tRNA is then liberated into the cytoplasm
waiting for the next initiator
•
Polypeptide chain termination
...
these codons do not code for any amino acid
thus are referred as non-sense codons
...
they are responsible for the termination of a genetic code
...
diagrams
...
s
...
Control of protein synthesis
...
•
The operon has two main sections- the structural genes and the operator genes
•
Structural genes are responsible for the production of polypeptide/protein which make
up an enzyme or group of enzymes
...
g
...
•
A third gene, the re
...
ulator gene is involved which is not part of the operon and may
be some distance from it on the DNA
...
Thus represses the production of particular enzymes
...
the inducer combines with the
34
repressor in a way that it prevents it from binding with the operator gene
...
g
...
•
Example, lactose combines with the repressor and prevents it from binding with the
operator gene which then switches on the structural genes
...
•
For enzyme repression, the co-repressor molecule, as it is called combines with the
repressor
...
these cease to produce mRNA and enzyme production ceases
...
g
...
the operator gene being repressed switches off the structural genes and the
production of tryptophan synthetase ceases
...
As such, it an example of cellular homeostasis
(feedback process)
...
g
...
All somatic cells of an organism carry the same gene, that is, they contain the same number
and types of chromosomes carrying the same alleles
...
Even within the cell, the rate of production of certain proteins varies
according to circumstances and demands
...
g
...
The operon
...
g
...
It comprises a closely linked group of structural
genes, coding for protein, and adjacent loci controlling their expression – an operator site and
a promoter site
a
...
35
•
a situation where some genes are normally switched on but may be switched off in
special circumstances
...
coli manufacture its own amino acid tryptophan, using a group of enzymes
tryptophan synthetase
...
•
the presence of tryptophan must switch off the appropriate gene
...
Enzyme induction
...
•
E
...
•
the presence of lactose in some way switches on the appropriate genes needed to
produce the enzyme
Control of metabolism
...
this enable the cell to produce the amount of enzyme required at
any given time to maintain the correct level of product
...
ne
...
ative feedback involving the inactivation would rapidly halt the pathway but would not
prevent the continued synthesis of the other enzymes
...
•
Must be able to store information that pertains to both development and metabolic
activities of the cell or organism
...
•
Must be able to replicate itself accurately during cell cycle and duplication and be
transmitted from generation to generation
36
•
must be able to undergo rare changes called mutation that provide genetic variability
required for evolution to occur
•
must be able to express the stored information when needed
...
•
should be able to cause transformation or change, by directing the formation of all
other structures of the organism
...
this is the sum total of all biochemical reactions taking place in the cell
...
there are two types of metabolic reactions
namely anabolism and catabolism
...
Anabolism
...
they often
involve condensation and are catalyse by enzymes
...
in animals it usually results in the building up of complex organic molecules
from simple organic substances e
...
6CO2 + 6H2O= C6H12O6 + 6O2
b
...
It involved the breakdown of molecules and usually release energy
...
E
...
cellular respiration
C6H12O6 + 6O2 = 6CO2 + 6H2O + ATP
...
This ensure a chemical balance
...
metabolic reactions take place stepwise and each step
is catalysed by an enzyme
...
Reasons why metabolic reactions occur stepwise
...
•
ensures that energy which is produced primarily in an inactive form (ATP) is made
available to the cells when necessary
...
Enzymes
...
they required in
small quantities that alters the rate of metabolic reactions in the cell but are not used up in the
course of the reaction
...
g
...
Properties of enzymes
...
•
only produced in living cells
•
they are soluble in water i
...
usually found in liquid form and never as solids
•
being proteins, they are coded for by DNA
•
they possess active sites where the reaction takes place
...
•
they lower the activation energy of the reactions they catalyse
•
their presence does not alter the nature or properties of the end product
•
they are very efficient
...
•
enzymes are highly specific i
...
each enzyme act only on a particular substrate or
group of substrates
...
amylase for example will only catalyse the
breakdown of starch
...
they have the ability to speed chemical reaction in the
body
...
38
•
enzymes are sensitive to temperature
...
•
enzymes are sensitive to pH
...
g
...
some enzymes such as pepsin work in acidic medium while trypsin in alkaline
medium
...
•
the catalysed reaction is reversible
...
•
some enzymes need to be activated by another substance before they can catalyse a
reaction
...
others include coenzymes and prosthetic
groups
...
Activation energy (En) of enzyme catalysed reaction
...
the greater the activation energy, the slower the rate of reaction
...
Diagram
...
Inhibitors binds with the enzyme on a permanent basis either on the active site or elsewhere
...
this occur more slowly than other forms of inhibition but with a
more devastating effects
...
An example is provided by the nerve gas diisopropylfluorophosphate
(DFP) designed for use in warfare
...
the enzyme destroys the neurotransmitter acetylcholine as
soon as the impulse has been passed from a nerve cell to a muscle
...
Allosteric enzymes
...
g
...
Compound binds to the enzyme at specific sites away from the active
site thus modify activity of the enzyme by causing reversible change in shape and structure of
the active site
...
Enzyme
do not have the same structure like the substrate
...
diagram
...
g
...
Example occur during glycolysis of cellular respiration in which ATP is produced
...
when cell metabolism increases, more ATP is used up decreasing it concentration thus the
pathway again comes into operation because the inhibitor ATP has been removed
...
e
...
g
...
there exist two types of
metabolic pathways i
...
linear and branched metabolic pathway
...
Reactions occurring inside the cells exist in sequence of gentle stepwise process
...
what actually happens is difficult to study
because studying them require killing the cell
...
the reactant
is isotopically labelled then introduced then introduced into a metabolic process and at the
end of the reaction the product is analysed using a mass spectrometer
...
THE oxygen of water molecule is
isotopically labelled 18O while the oxygen of CO2 is normal (16O)
...
it is realised that the O2 liberated is heavy (18O) thus originate from the water
molecule
...
Importance of metabolic pathways
...
•
sequence of reaction is often re
...
ulated by allosteric enzymes which help operate
through feedback inhibition
...
g
...
•
help in the production of substances that can be utilized in other pathways thus
increasing the efficiency of production involving enzymes
•
enable energy from the reactions to be derived in a usable form
...
g
...
•
This is re
...
ulation of metabolic pathways by the final substances produced
...
reactions only start when the concentration of the end product falls to a
sufficient low level
...
g
...
g
...
•
allosteric means different shapes and it is characteristic of such enzymes that they can
exist in two different forms, one active and the other inactive
...
thus for the enzyme to work the shape of the active site must be converted to fit
the substrate
...
shape of the binding substance has to fit that of the allosteric site in much
the same way as the normal substrate to fit the active site
...
g
...
it is produced by cellular
respiration and at high concentration, it acts as allosteric inhibitor stopping further
41
production
...
Differences between enzymes and inorganic catalyst
...
protein in nature
are not protein in nature
specific in action
are not specific in action
activated by cofactors
not activated by cofactors
catalyse reversible reactions
do not catalyse reversible reactions
sensitive to temperature and pH
not sensitive to temperature and pH
Produced by living cells
not produced by living cells
organic
inorganic
have active site on which substrate binds
do not have active site
differences between enzymes and coenzymes
...
are proteins
are not proteins
are catalyst
are not catalyst
have an active site
does not have an active site
sensitive to temperature
not sensitive to temperature
Classification of enzymes
...
•
names of substrate on which they acts
•
name of reaction they catalyse and
•
the end of the last word to suffix -ase e
...
dehydrogenase
...
42
1
...
they catalyse the transfer of specific groups from one compound to another
...
exple
glycogen + Pi (phosphorylase) = glycogen-1-1 phosphate
...
oxidoreductases
...
e
...
g
...
hydrolases
...
water
is involved in the reaction thus it is a hydrolysis e
...
lactose + H2O (lactase) = glucose + galactose
4
...
catalyse the addition of a group across a double bond e
...
pyruvic acid (pyruvic decarboxylase) = ethanol + CO2
...
Isomerases
...
E
...
glucose 1-phosphate (phosphoglucomutase) = glucose 6-phosphate
...
Ligases
...
The reaction uses energy that
comes from the hydrolysis of ATP to ADP and phosphate
...
Enzymes are used extensively in industries in the production of goods and services
...
1
...
A substance added to water to improve its cleaning properties that
is cause such nonpolar substances to go into solution in water
...
2
...
•
Saccharomycete cerivisae (yeast) contains the enzymes zymase, maltase and invertase
which help to break down sugar and ferment them into alcohol and CO2
...
3
...
43
•
Saccharomycete cerevisiae and S
...
proteases are also added
to convert protein into amino acid
...
4
...
•
Renin from the stomach of young ruminants is used in the making cheese from milk
...
Ruber
...
oxygen is then used to
convert latex into foam rubber
...
Coffee and sugar industry
...
44
CLASSIFICATION
Introduction to taxonomy
...
A more comprehensive way of studying these
organisms is required that organisms be arranged into related groups
...
Some of these ancient
approach grouped living things into flying animals and non-flying animals, edible and
poisonous plants etc which may seem odd to us
...
It is modified as we learn more about
living things but it is important to note that there is no single perfect system
...
Classification
...
Taxonomy
...
Classical taxonomy is based on morphology and anatomy
...
Systematics
...
It is
sometimes used as a synonym for *taxonomy
...
Biosystem
atic methods
include breeding experiments, biochemical work, and cytotaxonomy
...
Folk taxonomy
...
Artificial classification
...
or two easily recognizable characters
...
It is primitive since it group organisms with unsimilar characteristics
It is better used in field work
...
Natural system of classification
...
It takes into consideration internal and external features of the organism
It uses information from all the other branches of biology such as embryology,
morphology, anatomy, cell structure etc
...
Four different types of natural classification exist
...
Phenetic classification
...
It is to avoid the problem of establishing evolutionary relationships
which can be very difficult and controversial when there is little or no fossil evidence
...
Phylogenetic or Cladistics classification
...
Organisms belonging to the same group are believed to have a common
ancestor
...
3
...
This is the use of computers or mathematical procedures in
taxonomy
...
It uses a very large number phonetic characteristics to
classify organisms
...
4
...
It uses a mixture of phenetic and phylogenetic relationships to
classify organisms
...
Evolutionary relationships are mostly guessed thus this approach is a
compromise
...
To ease identification in the different parts of the world
...
To create order out of disorder
To produce an inventory of fauna and flora of a country, continent or the world
To produce a Latinised scientific name for every organism in the world both
living and extinct
...
To ease the study of living things
...
Organisms are grouped into formal taxonomic hierarchy called ranks
...
The highest taxon is at the top while the least at the bottom
...
Seven different taxa exist
that is 1
...
Phylum, 3
...
Order, 5
...
Genus, 7
...
1
...
This is the least taxonomic rank is the species and has
the following characteristics
...
2
...
they are members of closely related species but are not capable of
interbreeding e
...
goat and sheep
...
3
...
They are groups of closely related genera
...
Example man belong to family Hominidae while maize plant belongs to family
poaceae
...
Order
...
5
...
Groups of closely related orders
...
Phylum (Division)
...
Some taxonomist refers to phylum as division
...
Kingdom
...
Many phyla grouped to form kingdom
...
These are constructed for our
conveniences and can be modified or changed
...
At times the species name may be represented by sp
...
g
...
i
...
Plasmodium ovale, Plasmodium falciparum, Plasmodium vivax,
Plasmodium malariae
...
Consists of a series of groups within groups, from the most general (kingdom) to
the most specific (species)
There is no overlap between groups
The groups are based on shared features
...
Designating the species name
...
E
...
zebra = Equus burchelli
is named after someone called Burchell
...
E
...
the Nile crocodile is called
Crocodilus niloticus
...
E
...
hippopotamus is called Hipopotamus
amphibious due to its habits of living both in water and on land
...
This is a system of naming living things that was proposed by Carl Linnaeus (1707-1778)
which became the origin of modern classification
...
Rules for writing scientific names
...
The first name being the generic or
genus name while the second the specific epithet or species name
...
When the scientific name is hand written, it must be underlined separately and if
typed it must be in italics
48
Once the scientific name has been written in full in a text, in the same text genus
can be abbreviated with a capital letter e
...
Homo sapiens= H
...
The
species name is never used on its own
...
Sometimes abbreviation of names of persons who first described the species is
accepted at the end of the scientific name e
...
Solanum tuberosum L
...
Biological keys
...
There are three types
...
Dichotomous key
...
It considers one organism at a time
...
If we have ten
organisms, they could be separated into nine branches likewise if there are eight they
could be separated into seven branches
...
g
...
Feathers-domestic fowl, wings-grasshopper, fins or scales- tilapia, shell-snail, leaves
maize plant, hairs-rat
...
Numerical key
...
E
...
invertebrate key
1
...
Has hard body covering
3
...
Has two body regions (three body regions)
5
...
c
...
Organisms are separated using a dichotomous key but more than one
organism exist on each branch e
...
earth worm, housefly, cockroach, centipede
...
Wings absent- 15 pairs of le
...
scentipede
...
49
VIRUSES
...
They are the smallest living organisms
...
They cannot be seen with the light microscope and can pass through fitter paper that
retains the smallest bacteria
...
They have simple structure consisting of the following
Core-the genetic material either DNA or RNA which may be single or double
stranded
...
Capsid-which is a protective coat of protein surrounding the core
...
Nucleocapsid
...
This is found in viruses such as HIV and
Influenza
...
e
...
a
...
Life cycle of bacteriophage
...
Absorption
...
penetration and uncoating
...
, tail sheath contracts forcing hollow spike into cell aided by enzyme
lysozyme in base plate
...
3
...
Phage DNA codes for production of phage enzymes using
protein synthesizing machinery of host cell
4
...
Phage inactivates host DNA and phage enzyme
breaks it down
...
5
...
Phage DNA replicates itself and coat for new coat proteins
...
Assembly and maturation
...
Lysozyme is made by phage DNA
...
Release
...
Such life cycles are described lytic cycles
...
Each time host cell divide, phage DNA is copied with the host cell DNA thus
are described lysogenic phages
...
b
...
They have single stranded RNA instead of DNA
...
RNA is transcript into complementary DNA which then integrate itself
with the host DNA
...
The mRNA is
then translated into the unnecessary protein
...
This is the reason why
retroviruses are lethal
...
Other examples are tobacco mosaic virus (TMV) which causes a mottled
yellowing of tobacco leaves and hepatitis C virus which is the indirect causes of liver
cancer, tobacco mosaic virus
...
51
Droplet infection i
...
airborne such as common cold
...
By insects such as aphid e
...
cassava mosaic virus (CMV)
...
Through sexual intercourse with infected persons such as HIV
...
Through exchange of sharp object like needles, syringes, razor blade etc
...
Control of HIV
...
Cause diseases to plant and animals cmv, potato leaf roll virus, aids, measles, yellow
fever, common cold, poliomyelitis etc
...
KINGDOM MONERA OR PROKARYOTAE
...
They are unicellular or filamentous organisms consisting of extremely small cells
approximately 0
...
Flagella or cilia when present are simple and not constructed from a system of 9+2
microtubules
Reproduce mainly by binary fission though sexual reproduction is possible
Respiration is carried out by infolding of cell membrane called mesosome because of
lack of mitochondria or cytoplasmic membrane in cyanobacteria
Some are autotrophic while others are heterotrophic
...
Archaebacteria or primitive bacteria
...
2
...
They are true bacteria and compose of gram –ve and
gram +ve bacteria
...
Kingdom- Monera
Phylum- Schizophyta
Class- Schizomycetes
SN- Escherichia coli
CN- Escherichia
Habitat
...
This is because of the following reasons
...
Structure (9bs)
...
a
...
Bacteria are either autotrophic, saprophytic or parasitic
...
Other autotrophic forms make food
with energy from the oxidation of chemicals such as hydrogen sulphide and are called
chemosynthetic bacteria
...
It secretes enzymes
into the organic matter which is digested and soluble products absorbed and assimilated
...
Parasitic bacteria are either obligate or facultative parasite
...
b
...
The inner membrane is folded into mesosomes which have the respiratory enzyme and play
the role of mitochondria as in eukaryotic cell
...
Parasitic forms secrete enzymes and metabolite which becomes toxic to host cell
...
Some other forms are mutualistic thus live in close association with other organisms such as
nitrobacter in root noddle of leguminous plants e
...
groundnut, beans etc
...
Reproduction
...
Under favourable
conditions, bacterial cells divide by binary fission to form daughter cells
...
20
minutes is called the generation time meaning that if conditions are favourable, bacteria
population doubles after every 20 minutes
...
Forms of bacteria, examples and diseases
...
Differences between prokaryote and eukaryote
...
Mainly unicellular
Mainly multicellular except some protoctist
Cell division mostly binary fission no spindle
Cell division by mitosis or meiosis spindle formed
Cell size 0
...
Have 70s ribosomes
Have 80s ribosomes
Have fewer organelles
Have many organelles
Some fixed nitrogen
None fixed nitrogen
Chloroplast absent
Chloroplast present
Mesosomes and cytoplasmic membranes are used Mitochondria are used for respiration
for respiration
No ER
ER present
Plasmid present
Plasmid absent
Flagella simple lacking microtubules
Flagella complex with 9+2 arrangement of
microtubules
Example bacteria
Protoctist, fungi, plants and animals
...
55
Harmful effects
...
g
...
Cause food spoilage e
...
Clostridium botulinum
Decrease soil fertility such as denitrifying bacteria which convert soil nitrate to
atmospheric nitrogen
Attack root vegetables like potatoes, beets, carrots etc
...
Kill animals which are of economic value to man e
...
Bacillus anthracis that cause
anthrax in cow
...
Useful effects
...
Source of antibiotics e
...
streptomycin is produced by soil bacterium Streptomyces
...
g
...
coli in the colon of man
E
...
Nitrogen fixing bacteria increase soil fertility by converting atmospheric nitrogen to
soil nitrates
Used in cleaning oil spill such as Acinetobacter, Pseudomonas etc
...
g
...
e
...
g
...
Used in sewage treatment i
...
breakdown sewage to harmless form e
...
Zooglea
ramigera
...
What is a diagnostic feature of a living organism (xtics that enables the identification of the
organism to separate it from all other groups of organisms, enables the division of organisms
into taxonomic ranks)?
KINGDOM PROTOCTISTA
...
They are unicellular or multicellular
They are eukaryotic i
...
their DNA is enclosed by a nuclear membrane
Flagella or cilia when present are constructed from a system of 9+2 microtubules
Cytoplasm contains many membranous organelles and large ribosomes
Show diverse form of reproduction e
...
fission, budding, conjugation, fragmentation
etc
...
E
...
algae, amoeba, slime moulds, malaria parasite etc
...
General xtics
...
e
...
Have various methods of nutrition namely parasitic, holozoic and autotrophic
Reproduce asexually by binary fission, multiple fission or budding though a few
reproduce sexually by fusion of gametes or conjugation
Phylum Rhizopoda
They have pseudopodia which are used for locomotion and food capture
Most are free living and aquatic while others are parasitic such as Entamoeba
histolytica which lives in the small intestine of man
Their cells do not have a definite shape (amoeboid)
Class sarcodina
...
Amoeba proteus
...
Kingdom-Protoctista
Phylum-Rhizopoda
Class-Sarcodina
Sn-Amoeba proteus
Cn-Amoeba
...
They live in fresh water environment containing green vegetation such as ponds,
swamps and other stagnant water bodies
...
1
...
Retains protoplasm within the cell thus giving shape to the
cell
...
2
...
It consists of ectoplasm and endoplasm
...
3
...
It contains genetic materials which control all activities of the cell
4
...
Regulate the water content of the cell (osmoregulation)
5
...
Round organelles containing food particles surrounded by bubbles of
liquid on which the amoeba feeds
...
Mode of life
...
Locomotion
...
This type of movement is called amoeboid movement and is peculiar
to protozoans, white blood cells, sponges and slime mould
...
When it wants to move,
pseudopodia are formed in the direction of movement and cytoplasm flow into it while the
58
posterior parts are withdrawn
...
Another theory suggest that forward movement is
not caused by hydrostatic pressure but by a forward pulling force of some protein molecules
in the endoplasm
...
Nutrition
...
e
...
Food is taken in at any part of the cell by formation of pseudopodia
...
This is called cell eating or phagocytosis
...
Digestive enzymes are
secreted from the endoplasm which help digest the food
...
The undigested remains are passed out at any point on the cell
surface membrane
...
3
...
The respiratory surface in amoeba is the cell surface membrane
...
Oxygen
dissolve in water diffuses from the surrounding into the cell where it is used to
breakdown soluble food with the aid of respiratory enzymes to release energy CO2
and H2O
...
CO2 diffuses
out of the cell into surrounding water
...
Reproduction
...
It carries out
mostly asexual reproduction by binary fission
...
This begins with duplication of organelles in the cytoplasm, followed by
mitotic division of the nucleus into two daughter nuclei
...
At the end there is constriction of the cytoplasm
followed by complete separation of the cell surface membrane giving rise to two
daughter cells
...
It withdraws
pseudopodia and secretes a protective covering called a cyst around itself
...
Each nucleus will
constitute a spore and when the cyst breaks during favourable conditions, the spores
will germinate into new amoebae
...
Excretion and osmoregulation
...
Though the contractile vacuole assists in excretion, its main function is
osmoregulation i
...
control water content of the cell
...
In fresh water environment, water turns to move from the
surroundings into the amoeba by osmosis
...
This situation is
controlled by immediate development of the contractile vacuole which collect excess
water and move towards the cell surface membrane where it is eliminated alongside
small amount of salt
...
Phylum
...
General characteristics
...
Lack external structures for locomotion thus show limited movement
Cells have definite shape and are covered by a flexible pellicle
They are uninucleated and lack contractile vacuole
Asexual reproduction is by schizogony and formation of spores (sporozoites) while
sexual reproduction is by syngamy where large nuclei of spores are formed also called
sporozoites
...
Classification
...
N –Plasmodium vivax, ovale, malariae, falciparium
...
N –the malaria parasite
...
Man is the primary host while female anopheles’ mosquito is the secondary host
...
When an infected mosquito bites man, it injects sporozoites into the blood stream
...
In the RBC they grow and mature into trophozoites
Trophozoites multiply rapidly by schizogony to form more merozoites causing the
RBC to enlarge and burst releasing toxic substances throughout the body of the host
which causes fever
...
If a mosquito happens to bite an infected person, it sucks the gametophytes from
blood
...
Fertilization of male and female gametes produces a zygote which develop in the
mosquito’s intestinal walls and later differentiate into oocysts
...
Diagram
...
Through the bite of an infected female anopheles’ mosquito
Through blood transfusion
...
Causes high fever and vomiting
Causes anaemia
Causes joint pains and body weakness
Causes loss of appetite
Causes headache
61
Causes profuse sweating
It may lead to cerebral malaria
Methods of Control and Prevention of Malaria
...
Phylum
...
General characteristics
...
e
...
Show both asexual and sexual reproduction
...
They have chromatophore (cells are pigmented) which enable them to have colour
like in Paramecium
...
It lives in fresh water containing decaying organic matter
...
e
...
Structure
...
Locomotion
...
The cilia are used for swimming
...
This nature of movement of cilia permits the organism to rotate round
it axis
...
Respiration
...
Oxygen
diffuses along its concentration gradient from the surrounding water across the cell surface
membrane into the cytoplasm
...
CO2 which is a by-product of aerobic
respiration diffused from the cytoplasm across the cell surface membrane to the surrounding
water
...
63
Nutrition
...
e
...
It has an oral groove lined by cilia
...
At the end of the cytopharynx is a circular cytostome
where a vesicle is formed round the food particle with a small amount of water
...
Enzymes breakdown food into soluble and absorbable unit which are then
absorbed into the cytoplasm
...
Reproduction
...
Asexual
reproduction is by transverse binary fission
...
The micronucleus
the divide by mitosis producing two daughter nuclei each then move apart alongside
respective organelles
...
The
cell membrane and the pellicle divide along the longitudinal axis
...
One grow and develop into the mega-nucleus
while the other remain as a micronucleus
...
This occur mostly during shortage of food
and require two paramecia of opposite strains
...
It consists of the following stages
1
...
The pellicle breaks and cytoplasmic bridge is formed between the conjugants
...
3
...
, one remain
4
...
5
...
Gametic nuclei fuse to form a zygote thus exchange of genetic material is now
complete
7
...
The zygotic nucleus of each
exconjugant undergoes three successive mitotic division forming eight daughter
nuclei
8
...
Three micronuclei degerminate and binary fission of each exconjugant takes place
...
Another binary fission results in the separation of the mega-nuclei while micronucleus
again divides by mitosis
...
Osmoregulation
...
It consists of vesicles with radiating canals
...
This water is later expelled across the pellicle to the
surrounding
...
Subkingdom
...
They are aquatic plant-like protoctist
Have a cell wall made up of cellulose as in green plants
Have diverse forms i
...
some are unicellular such as chlorella, chlamydomonas,
colonial forms such as volvox, filamentous such as spirogyra and thalloid form such
as fucus
...
Carryout autotrophic nutrition due to the presence of chloroplast containing the green
pigment chlorophyll that trap sunlight during the process of photosynthesis
...
Have pyrenoid or paramylum for the storage of excess starch
...
Some forms are motile with flagellium while others are sessile and attached on
surfaces of rocks
Reproduction is both asexual and sexual
...
NB
...
Isogamy – This is the fusion of two gametes which are identical
...
Anisogamy – this is the fusion of two gamets which are slightly different in size and
behaviour
...
66
3
...
The male gametes
are small, motile, ciliated, active, and initiative while the female gametes are large,
non-motile, non-ciliated, passive and receptive
...
Type of photosynthetic pigment
Type of food reserve
Present of flagella
Fine structure
...
General characteristics
...
It masks other pigment such as
xanthophyll and carotene giving the algae their green colour
...
Their cell walls are made up of cellulose
...
E
...
spirogyra has spiral chloroplast, chlamydomonas and chlorella has cup-shaped
chloroplast etc
...
Some are motile i
...
use their flagella and cilia to move e
...
chlamydomonas
...
Classification
...
Phylum – Chlorophyta
Class – Chlorophyceae
SN – Chlamydomonas nivalis
...
Habitat
...
e
...
Structure
...
1
...
It has a cup-shaped chloroplast which contain the pigment chlorophyll
...
2
...
It has two whip-like flagella which beat toward direction of movement
and the whole body rotate toward a fixed direction in a zigzag manner
...
Reproduction
...
Asexual reproduction is through binary fission
...
Thus about eight or sixteen daughter cells are produced
...
This is a
resting or dormant stage where a large amount of gelatinous matrix is secreted and
released only when conditions are favourable
...
Diagrams
...
Spirogyra
...
Phylum – Chlorophyta
Class – Chlorophyceae
SN – Spirogyra adnata
...
Habitat
...
e
...
Structure
...
The entire body surface is
covered by mucilage which makes the organism slippery to touch
...
Nutrition
69
It an autotrophic organism
...
Chlorophyll
help to trap sunlight energy during the process of photosynthesis
...
CO2 produced as a result of tissue respiration
diffuse into the surrounding water
...
Reproduction
It carries out both sexual and asexual reproduction
...
Each fragment or cell is
capable of regenerating a new filament with diploid cells
...
Two opposite strands or conjugants come and lie side by side
Outgrowth or projections called protuberance are formed on each strand
Cytoplasmic content constricts
Haploid nucleus increase in size
Protuberance meet and cross walls breakdown forming conjugation tube
Male nucleus (gamete) flow into female nucleus (gamete) by amoeboid movt
The male gamete fuse with the female gamete to form a zygote
The zygote develops into a zygospore with a thick wall
The zygospore drop to the bottom of the pond
The thick wall zygospore undergoes meiosis to form four haploid cells, three of them
degenerate
In favourable conditions the remaining haploid cell germinate into a new filament
...
General characteristics
...
Their main photosynthetic pigment is chlorophyll A and B though some species have
xanthophyll
...
asexual reproduction is by longitudinal binary fission while sexual reproduction is
rare
...
I
...
Classification
...
It leaves in stagnant water such as ponds containing organic matter like faeces of animals
...
Mode of life
...
It swims fairly rapid in water due to lashing of the flagellum
...
As it moves ahead, its rotating action
stir the water to confuse it predators
...
e
...
Respiration
...
Oxygen dissolve in water
diffuse from surrounding water into the cytoplasm where it is used in the breakdown of food
to release energy while CO2 resulting from tissue respiration diffuse out of the cytoplasm
into the surrounding water
...
Nutrition
...
72
Autotrophic nutrition is through the process of photosynthesis
...
Excess food is stored as starch
in paramylon body
...
Heterotrophic nutrition takes place in the absence of sunlight
...
Excretion and osmoregulation
...
The contractile vacuole has smaller channels
through which liquid waste is discharge into the main vacuole
...
Reproduction
...
During this, the organism comes to rest and secretes a mucilage to cover itself
...
The cytoplasm divides into two
starting from the anterior end
...
During unfavourable conditions, it forms a hard resistant covering called a cyst
...
Plant-like characteristics of Euglena
...
Undergoes autotrophic nutrition through the process of photosynthesis
...
Has flagella for locomotion
Has eye spot which is photosensitive
Has a rigid pellicle which is associated to most protozo=]ans
Undergoes heterotrophic nutrition
...
General characteristics
...
This gives them brown colour hence they are called brown algae
They are almost marine with very few species living in fresh water
...
Vegetative is by fragmentation,
asexual by spores (motile zoospores) while sexual is by isogamous or oogamous
gametic fusion
Excess carbohydrate is stored in the form of laminarin, mannitol
They have an undifferentiated body called thallus
Have strong and flexible midrib which limit them from breakage
They have air bladders which permit floats on water (buoyancy)
They are all sessile and attached themselves to surfaces of rocks with the help of a
hold fast
...
Classification
...
74
Structure
...
Fucus reproduces both sexually and asexually
...
When detached, it
develops into fully grown matured brown algae
...
At the tip of a mature dichotomously branched thallus is found swollen
receptacle
...
In monoecious species, a
conceptacle contains both male and female reproductive structures
...
Diagram of flask shape conceptacle
...
The antheridium undergoes meiotic
division to produce bi-flagellates antherozoid
...
The egg secretes a chemical substance which attract the antherozoid
(chemotaxis)
...
When conditions are favourable the zygote develops into dichotomously
brown algae
...
Thus it produce heterogametes called antherozoids
and eggs
...
In protandry the male
reproductive structure matures before the female reproductive structure of the same algae
while vice versa for protogamy
...
75
It has holdfast that anchored it firmly on the surface of the rock or substrate making it
difficult for the fucus to be dislodge by waves
...
Has air bladder to enable it float in water (buoyancy)
...
It dominant photosynthetic pigment is fucoxanthin which enable it to trap sunlight of
lower wave length
...
Chloroplast is mainly located in the surface for maximum exposure to sunlight for
photosynthesis
...
Economic importance of Algae
...
These bloom cause
the water to have an unpleasant smell and taste and may lead to depletion and
death of fish (eutrophication)
Cause red rust in tea plant (Camillia sinensis) such as cephaleuros parasiticus
Many blue green algae like Anabaena produce certain toxic compounds which
have been seen to either induce harmful effects like loss of weight, weakness,
abortion, etc
...
Some algal species cause skin diseases (swimmers itch)
...
Useful effects
76
Primary Producers
...
This form the bases of all food chains
...
They are also useful in decreasing water
pollution by releasing oxygen
Algae are used as food in several countries and in several forms
...
Laminaria species is
the important edible seaweed in Japan and the food item 'Kombu' is prepared from
it
...
Unicellular algae like
Chlorella are easily cultivated and can be used as a source of single cell protein
for humans and animal consumption
...
Blue-green algae are treated as bio-fertilizers from olden days
...
All these algae fix the atmospheric
nitrogen
...
Sea algae are used as food for fishes
...
Some green-algae, diatoms, some bluegreen algae
are used as food material to fishes
...
The antibiotics chlorellin obtained from chlorella is effective
against a number of pathogenic bacteria
...
Algae such as chlorella are used in space ships and nuclear submarines as oxygen
regenerating, food and water recycling organisms
...
Brown seaweeds called kelps yield potash soda and iodine
...
Bromine are
extracted from some red algae
...
Iodine industry is mainly dependent on algae
...
g
...
Agar-agar is a jelly-like substance of great economic value
...
Agar is used in culture medium for growing callus in tissue
culture
...
It
is used as an emulsifier in pharmaceutical, textile, leather, cosmetics and brewing
industries
...
It is used in various industries like glass, metal polishing,
paint, toothpaste, soaps etc
...
Algae in sewage disposal
...
are living in sewage water
...
Some green algae have symbiotic relationship with fungi forming lichens which
usually occur on the bark of trees
...
Produce coral reefs
Diatoms are used in the production of glass and polish
...
Some species like Chlamydomonas, Chlorella, etc
...
They
are mainly useful to clean the water by releasing oxygen and also modify the
carbonate material in the water into N, P, K fertilizers
...
Differences between Chlorophyta, Euglenophyta and Phaeophyta
...
e
...
Also store
Mostly fresh water
...
fat
Fresh water
...
e
...
thalloid
Cell wall of cellulose
Has pellicle instead of cell Cell wall of cellulose
wall
Eyespot
and
contractile Eyespot contractile vacuole Eyespot
and
vacuole in some species
and flagella always present
vacuole absent
Hold fast absent
Hold fast absent
Hold fast present
Air bladder for buoyancy Absent
Present
absent
79
contractile
KINGDOM – FUNGI
...
The mycelium may be loose as in Rhizopus or compact as in mushroom
...
They reproduce sexually and asexually
The gametes and spore produce lack flagella
Photosynthetic pigments are absent
...
e
...
Most fungi are non-motile though their reproductive structures may be motile
They are grouped into six phyla namely Zygomycota, Ascomycota, Basidiomycota,
Deuteromycota, Oomycata and Myxomycota
...
General characteristics
...
The hyphae of some species have cross-walls and are said to be septate
...
Asexual reproduction is by formation of
sporangia containing spores or conidia while sexual reproduction is by conjugation
...
Case study
...
80
Habitat
...
Classification
...
SN-Rhizopus nigricans, CN-breadmould
...
Mode of life
...
It carryout saprophytic nutrition
...
Rhizoid of the fungus grow into the substrate or organic matter or food,
secretes enzymes into it
...
are absorbed
...
Reproduction
...
Asexual reproduction is by the formation of sporangiosphores especially during favourable
conditions
...
The sporangium is
separated from the sporangiophore by a sterile dome-shaped columella
...
These masses develop into spores with thicker and darker walls
...
When the spores become fully mature, the
columella exert pressure that causes the sporangium to burst releasing spores
...
When the spores fall on a suitable it grows into a new mycelium
...
This is by conjugation and occur during adverse conditions such as drought and lack
of food
...
At
times the hyphae may be from different mycelia
...
81
Progamatangia touch and push each hypha apart
...
The progametangia becomes the gametangium containing gametes
...
The diploid zygote undergoes meiosis to form four haploid cell, three degenerate
...
The haploid nuclei develop into a haploid spore
...
What are the differences between conjugation in Spirogyra and Rhizopus
...
General characteristics
...
The body is a mycelium, having a network of fine tubular filament called hyphae
The hyphae are branched with cross-walls and are said to be septate
...
Asexual reproduction is by formation of
conidia and no sporangia while sexual reproduction is by formation of ascospore in
special structures called ascus
...
Case study I-Yeast
...
It grows in sugar solution, palm wine and overripe fruits
...
Kingdom-Fungi, Phylum-Ascomycota, Class-Ascomycetes, Genus-Saccharomyces, Speciescerevisiae
...
, CN-yeast
...
Nutrition and respiration
...
e
...
In the presence of oxygen, its convert glucose in sugar to carbondioxide and water
...
In the absence of oxygen, the sugar is
82
converted into carbondioxide and alcohol (fermentation)
...
That is the CO2 produced make dough to rise
...
Asexual reproduction
...
During this, a small portion of the cell wall becomes soft and bulge outward allowing
the cytoplasm to flow into it
...
The bud maybe separated by formation of constriction or remain attached
...
Sexual reproduction
...
They associate in pairs and protuberance are formed which join to form a conjugation
tube
...
The haploid nuclei fuse to form a zygote which behaves as an ascus
...
Each forms a wall around itself, enlarges and become an ascospore
...
When the ascus split open the
haploid ascospore are liberated
If they fall on a suitable habitat, they germinate into a new mycelium
...
Habitat
...
e
...
Some on the soil, air as dust, water
spores), on decaying organic matter such as fruits, vegetable etc
...
Kingdom-Fungi, Phylum-Ascomycota, Class-Ascomycetes, Genus-Penecilium, Speciesnotatum
...
83
NB-it secrete a chemical substance called penicillin which is an antibiotic
...
Bacteria have a special protein in their cell wall called
peptidoglycan hence the antibiotic prevent formation of peptide bonds in this protein
...
Phylum Basidiomycota
...
Reproduction is only sexual through the formation of basidiospore inside the
basidium, sexual reproduction is completely absent
...
Have mycelium with hyphae which are septate
...
Case Study-Mushroom
...
Kingdom-Fungi, Phylum-Basidiomycota, Class-Basidiomycetes, GenusAgaricus, Species-compestris
...
Habitat-it grows on decaying tree trunks, dung and organic matter in the field
...
The mature fruiting body is made up of compact sporophore
...
Below the cap are reproductive structures
called gills
...
Sexual reproduction occurs within the basidia
...
Life cycle of Agaricus compestris
...
Each
basidia forms haploid basidiophores which are attached to the basidium by a stalk called
sterigma
...
The two nucleus of binucleated
cells fuse to form a diploid zygote which divide twice mitotically producing four haploid
nuclei
...
These four haploid nuclei squeeze through the
narrow neck of the sterigma with some cytoplasm to form resistant basidiospores
...
When conditions are favourable,
it germinate forming hyphae with mononucleated cells
...
Terminal cells of the gills produce basidia with
basidiospores and the cycle continuous
...
General characteristics
...
Obligate parasite has a single host while facultative parasite has alternate host in order
to their life cycle
...
Asexual reproduction is by formation
of haploid spore formed inside sporangium while sexual reproduction is by formation
of zoospores and oospores
...
They feed using special hyphae called haustoria which penetrate host cells and end up
destroying them
...
Classification
...
SN- Phytophthora infestan, CN-potato blight
...
It is a parasite that infect potatoes causing potato blight
...
The asexual spores once present in the spongy mesophyll cells of the leaf, it germinates into
branched hyphae
...
Haustoria produce an enzyme which digest host cells into soluble product which are absorbed
by hyphae of the fungus
...
When sporangium split opens, it
releases haploid spores which are very resistant to adverse conditions
...
The spores can penetrate host
plant through the stomata, lenticels in the stem
...
Late blight is a diseases of tomato, potato, huckleberry etc
...
Life cycle
...
Harmful effects
...
Some are poisonous when eaten e
...
Aminata phaloides or “death cap”
...
Cause food spoilage e
...
breadmould
Destroy houses and furniture such as dry rot
...
Serves as food such as common field mushroom (Agaricus compestris)
Serve as a source of antibiotics e
...
the fungus Penicilium notatum produces the
antibiotic penicillin which is used universally to treat sore throat, abscesses etc
...
This is from the fermentation of sugar from sugar
cane
Yeast is used in the production of alcohol in brewery industries
...
Yeast is used in bakeries where they ferment carbohydrates in bread dough to produce
CO2 which causes the dough to rise while alcohol evaporate during baking
...
It makes the cheese to ripen and give flavour to
it
...
g
...
Help in the decay of dead plants and animals thus release nutrients like CO2, water
and NH3 to the environment
...
They form symbiotic relationship called lichen and mycorrhiza
...
KINGDOM PLANTAE
...
The vegetative body is divided into roots, stem and leaves
...
Asexual reproduction is by vegetative
propagation while sexual reproduction is by gametes formation
Their cell wall is made up cellulose
Have a vascular bundle made up of xylem and phloem
Undergo alteration of generation in the life cycle
...
Cytoplasm contains many membranous organelles and large ribosomes
...
This kingdom is classified into many phyla namely- phylum Bryophyta, Filicinophyta,
Coniferophyta and Angiospermophyta
...
General characteristics
...
Show distinct heteromorphic alternation of generation in which the diploid sporophyte
is totally or partially dependent on the gametophyte for nutrition and support
...
Their rhizoids are multicellular and are used for anchorage and absorption of water
and mineral salts
...
They are known as amphibians of the plant kingdom since part of their life cycle
requires water while the other requires dry conditions
...
Class-Musci
...
Moss plant
...
Funaria hygrometrica
...
Habitat
...
Structure
...
The
rhizoids or pseudo-roots are used for anchorage and absorption of water and mineral salt from
the soil
...
The mature
sporophyte consists of a foot which attaches it to the gametophyte, the seta or stalk which
carries the capsule at it apex
...
Asexual reproduction takes place by the formation of gemmae usually in groups at the apex
of the leaflet
...
The protonema then grows into a new gametophyte
...
The life cycle of moss has two alternating phases
...
e
...
The
moss plant is the gametophyte and at maturity, it bears the sporophyte generation which
depends on it for food and support
...
The spherically shaped antheridium produces bi-flagellated antherizoids
88
(sperm) by mitosis while the archegonium produces a large eg g or ovum
...
The gametophyte of most mosses are monoecious antheridia and
archegonia are borne on the same gametophyte or plant though a few are dioecious
...
When there is sufficient moisture, the antherozoids or sperm are
released from the antheridia which swim in the moisture in the neck of the archegonium
attracted to the venter by chemotaxis
...
The zygote is the beginning of the sporophyte generation
...
e
...
The foot penetrates the base of the venter and grows into the apex of the leafy
shoot
...
The
seta elongates and expand at its tip to form the capsule covered by the calyptra
...
Meiosis occurs in the capsule and
each diploid spore mother cell produces four haploid spores
...
When the
structure is dry they open out and the spores are dispersed by wind
...
Alternation of generation in the moss plant
...
e
...
In the moss plant, there is distinct alteration of generation in which the gametophyte alternate
with the sporophyte generation to complete its life cycle
...
The sporophyte
depends on the gametophyte for nutrients and support
...
The gametophyte generation begins with the germination of spores
and include the protonema, leafy shoot bearing gametangia and gametes while the sporophyte
begins with the zygote and include the foot, seta and capsule containing diploid spores
...
characteristics
...
The capsule of the sporophyte has elaters essential for spore dispersal
They are dioecious having different male and female gametophyte
...
The filamentous protonema stage is generally absent in thalloid liverworts
...
Liverworts
...
Kingdom-Plantae, Phylum-Bryophyta, Class-Hepaticae, SN-Marchantia
polymorpha, CN-liverworts
...
It grows on damp shady environment such as river banks, springs, ponds, rocks and
wet old walls
...
Structure
...
It lacks true roots but has unicellular hair-like structure called rhizoids which assist in
anchorage and uptake of water and minerals
...
Gemma cups contain gemmae which if dispersed can germinate under favourable
conditions into a new haploid gametophyte
At maturity the male gametophyte develop a stalk called antheridiophore at the tip of
which is found the antheridia head
...
90
The paraphysis retained water within the antheridia head keeping it moist to prevent
desiccation
...
On top of a mature haploid female gametophyte is found a stalk or archegoniophore
bearing archegonia head which is star-shaped
...
The haploid female gametophyte has gemma cups containing gammae for asexual
reproduction
...
Asexual reproduction
...
Gammae
are flattened, more or less circular in structure which can detach and grow into new
dichotomous thalli
...
Marchantia has separate male and female plant (dioecious)
...
Within the antheridium are numerous antherizoid mother cells
which undergo mitosis to form small bi-ciliated spindle-shaped antherizoids
...
The under surface of this receptacle has flask-shaped archegonia, each with a
large egg cell or ovum formed by mitosis
...
They swim in
the watery medium and are attracted to the archegonium by chemotaxis
...
The zygote develops a
thick wall to become an oospore or embryo
...
The sporogonium consist of a foot embedded
in the archegonium and a seta which bears a capsule
...
When the capsule mature with
spores, it breaks and liberate the spores
...
The life cycle of Marchantia show alternation of generation i
...
the haploid gametophyte
reproduces sexually by fusion of gametes and give rise to diploid sporophyte which
reproduces asexually by spore formation to give rise to the sporophyte
...
91
Adaptations of bryophyte
...
Have rhizoids for anchorage, uptake of water and minerals salts
...
Adaptations of Marchantia to their habitat
...
Have a flat thallus for maximum absorption of sunlight for photosynthesis
...
Phylum Lycopodiophyta
...
The vegetative plant is the diploid sporophyte generation
...
Have vascular bundle i
...
xylem and phloem
...
The roots and stem are dichotomously branching
They are usually referred to as club mosses due to the manner in which they colonise
their habitat
...
Growth is from an apical meristematic cell
...
Homospory are plants that produce the
same type of spores (mega or microspore) while heterospory are plants that produce
different types of spores i
...
the mega spore is structurally and functionally different
from the microspore
...
Lycopodium
...
Kingdom-Plantae, Phylum-Lycopodophyta,
Lycopodium clevatum, CN-Lycopodium
Class-Lycopodinae,
SN-
Habitat
...
Structure
...
It has true root stem and
leaves with vascular bundle (xylem and phloem)
...
The stem is slender with
dichotomous aerial branches
...
At the end of some branches are reproductive structure called strobilus
(strobili)
...
Leaves are sessile and lanceolate with
distinct midrib not quite reaching the apex, drown out into a sharp point
...
It carries out sexual and asexual reproduction
...
Sporophylls are smaller in size and arranged on the apex of branches in the form of strobili
(strobilus)
...
Diploid spore mother cell undergoes meiosis to form haploid spores which
are resistant and can survive adverse conditions
...
It a tunerous
body with a lobed crown that bears antheridia and archegonia
...
The venter
of each archegonium contains one egg cell or ovum
...
The zygote then grows and develops into the
sporophyte
...
The sporophyte generation is
independent of the gametophyte generation
...
Diagram
...
Classification
...
It grows on damp places on hills and plains
...
It is a slender dichotomously branched and creeping plants on damp walls and
ground
...
The stem
bear four row of leaves i
...
two rows of small leaves on the upper surface and two rows of
larger leaves on the lower surface
...
The club-shaped strobili are
situated at the tips of the creeping stems
...
Reproduction and life cycle
...
Asexual reproduction
...
Leaves on the
lower surface produce megasporophylls which bear megasporangia while those on upper
surface produce microsporophylls bearing microsporangia
...
In both
cases, the diploid spore mother cells undergo meiosis to produce haploid spores
...
The microspores germinate to form male gametophyte while the megaspore form female
gametophyte
...
The male gametophyte is reduced in size,
non-photosynthetic and depends on food stored in the microspore
...
It develops rhizoids and becomes partially green and photosynthetic after detachment
and produce archegonia at its surface
...
In the presence of moisture, the antheridium burst releasing male gametes or sperm
...
The megaspore may still
be on the parent sporophyte or may have been released
...
The zygote develops into an embryo sporophyte with a
suspensor that pushes the embryo into the food store of the gametophyte and megaspore
...
Note that in selagenella, the mature gametophyte is not an independent plant
...
This is an important adaptation to life on land since the gametophyte is vulnerable to
desiccation
...
Have thin filament called rhizoid instead of true roots which help in anchorage,
absorption of water and minerals from the soil
...
Has rhizophores which branch to give rise to adventitious roots
Has erect open sporophyll for easy dispersal of spores
The dichotomously branched stem helps the plant to spread and colonise its habitat
Leaves and stem contain green pigment chlorophyll for photosynthesis
The gametophyte is protected within spores to prevent desiccation
The leaves are very small in size to reduce water loss by evapotranspiration
The bi-flagellated antherozoids are capable of swimming in water to fertilize the egg
inside the venter
...
Characteristics
...
They produce same kind of spores i
...
they are homosporous
...
Fern plant
...
Kingdom-Plantae, Phylum-Filicinophyta, Class Filicinae, SN-Dryopteris
filix-mas, CN-fern plant
...
They are found in moist shaded forest floor or environment and deep valleys
...
Few resistant species grow on the
open field
...
Fern is a diploid vegetative plant divided into true root, stem and leaves or fronds with
vascular bundle
...
Young fronds are
rolled into spirals fiddle head consist mainly of meristematic tissues
...
The fronds or leaves are compound and pinnate with a
rigid prolonged petiole called rachis from where leaflet or pinnae arise
...
The sori may be covered a
membrane called indusium
...
Sori are
arranged in rows behind the pinnules which protect the sporangia from drying
...
The
sporangium contains 16 diploid spore mother cell that undergo meiosis to produce 64 haploid
spores
...
(diagram)
...
The annulus and stomium lose water and their cytoplasm begin to shrink
...
This causes the cells of the to rupture and those of the annulus to curl back
...
Finally, the cytoplasm pulls away
from the annulus walls returning the tension across the annulus so that it returns violently to
its original position, dispersing the remaining spores
...
The fern plant carryout both asexual and sexual reproduction
...
The sporophyte produces spores in structure called sporangia
...
All
spores are identical thus fern plant is homosporous
...
The spores
are dispersed as described above
...
95
When the spores fall on a suitable habitat, it germinates into a heart-shaped haploid
gametophyte or prothallus
...
The gametophyte is usually buried in the
ground
...
The archegonium contain a neck and a venter with an egg or ovum while the
antheridia produces antherizoids or multiflagellated sperms
...
This is a chemical response or chemotaxis due to malic acid secreted by the
cells in the neck of the archegonium
...
The zygote develops into an embryo which is nourished by the
prothallus or gametophyte
...
Alternation of generation in the fern plant
...
The diploid sporophyte and the haploid gametophyte are
independent of each other
...
The sporophyte generation is more complex and is the main vegetative
body of the plant while the gametophyte is highly reduced and does not depend on the
sporophyte for support or nourishment
...
Water is used for photosynthesis by the vegetative plant as well as the heart-shaped
gametophyte
...
Water assist in the germination of the haploid spores into a heart-shaped gametophyte
Water is used in the opening and closure of stomata
...
General Characteristics
...
The vegetative plant body is made up of true roots, stem and leaves
...
Xylem is made up of tracheid while
phloem has albuminous cells similar in function to companion cells
...
Bear reproductive structure called cones composed of sporophylls not flowers
...
Seeds are formed after a single fertilization and each has more than 2 cotyledons (215 cotyledons per seeds)
...
They are heterosporous with the microspore different from the megaspore
...
They grow under cold arid conditions especially in the Western Highlands of
Cameroon (Northwest and West Regions)
...
Case study I
...
Kingdom-Plantae, Phylum-Coniferophyta, Class-Coniferinae, SN-Pinus sylvestris, CN-scot
pine
Habitat
...
Structure
...
Has well
developed tap root system and a stem with numerous aerial branches
...
Long branches are developed from lateral buds in spring
and are arranged in whorls
...
Dwarf branches show limited growth and carry numerous leaves
that is long green needle-like leaves which usually occur in clusters
...
Leaves have sunken stomata, thick cuticle
to limit transpiration
...
The rough stem is
equally covered with a scally bark, which peels off in strips
...
The pine tree is monoecious and the reproductive structure is the cone
...
The male cone
consists of microsporophyll while the female cone consists of megasporophyll
...
Male cones
develop and mature long before the appearance of the female cones to facilitate cross
fertilization
...
Consist of microsporophyll which contains microsporangia
...
At maturity, it undergoes meiosis to produce four haploid
cells or microspores which develops into the pollen grain or male prothallus or gametophyte
...
One becomes the generative nucleus and the other the pollen nucleus
...
97
The female cone
...
Each ovuliferous scale bear
two ovules on its upper surface
...
Below the integument is the nucellus within a single spore mother cell differentiates
...
The female gametophyte or prothallus contains two or
more archegonia, each with a single egg cell which mature very slowly
...
During pollination, wind transport pollen grains which are deposited directly on the ovules
found on the ovuliferous scales of the female cone
...
The pollen tube enters the
megasporangium through the micropyle and is nourished by the nucellus
...
Fertilization is once and takes place a year after pollination
...
The seed are naked
Diagram life cycle of pine
...
Classification
...
Habitat-Arid soil
...
Cypress is heterosporous that is produce two types of spore microspore and
megaspore
...
The megasporangium contains diploid spore mother cell
...
They are xerophytic plants growing on
arid soil hence develop scale-like leaves to reduce amount of water loss by
evapotranspiration
...
Diagram
...
General characteristics
...
The plant body is differentiated into true roots stem and leaves
...
98
Some species are monoecious while others are dioecious
...
Have photosynthetic pigment chlorophyll found in the chloroplast
...
Class-Monocotyledoneae
...
Lack secondary meristematic tissues (cambium)
They are usually herbaceous
...
Have two cotyledons per seed
Flower parts are in four or five or their multiples (tetramerous or pentamerous)
Leaves have net venation and are broad with a petiole
Have tap root system
Exhibit epigeal germination
Vascular bundles of the stem are arranged in rings
Have secondary meristematic tissues (cambium) between xylem and phloem
responsible for secondary thickening
...
Sexual reproduction in flowering plants
...
I-
These are whorls of modified leaves which represent the reproductive organ of the
plant
...
A bisexual flower consists all the
essential parts of a flower and is called a complete flower while a unisexual flower
is an incomplete flower
...
Male and female sex organs are borne on the same
plant
...
The male and female sex organs are borne on separate
plant
...
e
...
g pawpaw
...
Separate male and female flowers borne on the same plant e
...
maize plant
...
Diagram
Main parts of the flower
...
It is the top of the flower stalk from which the floral parts arise
Parianth
...
This is a collection of sepals
...
At times they are brightly coloured to attract
insect for pollination
...
Polysepalous when sepals are separate or free
...
This is a collection of petals
...
In wind pollinated
flowers the petals are usually reduced in size and green or may be entirely absent
...
Polypetalous when petals are separate or free
Sympetalous or gamopetalous when petals are fused such as in Ipomoea batata or
sweet potato, morning glory etc
...
Androecium
...
Each stamen consists of an anther, a filament
...
The filament contains a vascular bundle that
carries food and water to the anther
...
This a collection of carpels that forms the female reproductive organs of
the flower
...
The stigma receives the
pollen grains during pollination and the style bears the stigma in a suitable position in
the flower to receive the pollen
...
Ovules are the structures in which the embryo sacs
develop and which, after fertilization becomes the seed
...
NB
...
Epigynous if the stamen and parianth are inserted above the ovary
...
A superior ovary is one located above the other floral parts on the receptacle i
...
ovary
of an hypogynous flower
...
e
...
Nectaries are glandular structures that secretes nectar, a sugary fluid that attract
animals for pollination usually insects but also birds and bats in the tropics
...
This is a vertical plane or line through which a flower can be divided into two exact equal
halves
...
101
Actinomorphic symmetry is when members of each whorl are all alike and arranged
radially around a central axis
...
This flower can be divided into two equal halves which are mirror images
of each other through any plane such as in hibiscus flower (Hibiscus rosa-sinensis)
...
When floral parts are different from each other in shape
...
Such flowres can
be divided into two halves which are mirror images of each other only through one plane as
in Crotalaria (rattlewort), bean, pea etc
...
Aestivation
...
There are several types
...
Twisted or contorted aestivation-when one margin of the petal or sepal overlaps that
of the next
...
Imbricate aestivation
...
Others are external and overlap each other on one margin
...
Vexillary aestivation
...
This is found mostly in family Papilionaceae such Bean, Pea,
crotalaria etc
...
This is the arrangement of ovules within the ovary
...
This can be marginal
...
Types of placentation
...
The ovules develop in rows near the margin on the placenta formed along
ventral suture
...
102
Parietal
...
It occurs in bicarpellary or multicarpellary but
unilocular ovary
...
g
...
Axile
...
It occurs in bi to multilocular ovary
...
g
...
Free central
...
It occurs in multicarpellary but
unilocular ovary e
...
Primulaceae
...
Ovules develop over the entire inner surface of the carpels
...
g
...
Basal
...
E
...
Asteraceae
...
A floral diagram is the ground plan of a flower indicating the number of floral parts, their
general structure, arrangement and the relation they have to one another and their position
with respect to the mother axis
...
Sepals and petals are
represented by crescents and if they are slightly different, they are distinguished by some
slight changes of the crescent
...
The gynoecium is shown as it appears in transverse section
...
Adhesion of adjacent
whorls is represented by a straight line joining the parts concerned
...
Floral formula
...
In floral formula,
103
K=Calyx, C=Corolla, A=Androecium, G=Gynoecium
...
each symbol is followed by a
number which represents the number of parts in the whorl e
...
K5 means calyx with five
separate sepals
...
g
...
Where more than one whorl occurs
in a set, a plus sign separate members of each whorl e
...
C3+3 means the corolla with two
whorls each consisting of three separate petals
...
A line drawn above or below G shows the
position of the ovary
...
e
...
G (5) means a gynoecium with five fused carpels of a superior ovary
...
e
...
The sign (+) before a floral formula indicates the
flower is actinomorphic and % shows the flower is zygomorphic
...
Development of pollen grains
...
The anther
contains four pollen sacs with numerous diploid pollen mother cells
...
The young pollen grains occur
in groups of four called tetrads
...
The outer
wall called the exine is made up of a waterproof substance called sporopollenin
...
The pollen matures when its
nucleus divides by mitosis to produce a generative nucleus and a pollen nucleus
...
Development of the ovule or egg
...
Ovules are attached to the ovary wall at a point called the placenta by a short stalk
or funicle through which food and water pass to the developing ovule
...
The integuments are discontinuous and form a gap or pore at one end of the ovule called
micropyle
...
This diploid cell undergoes meiosis producing four haploid
cells
...
As the embryo sac
grows its nucleus undergoes three successive mitotic divisions forming eight nuclei (four at
each end of the embryo sac)
...
The remaining six nuclei (three at
each end) become separated by thick walls
...
105
Assignment-draw floral diagrams and floral formulae of the following
...
Pollination
...
There are two types of pollination
Self-pollination is the transfer of pollen grains from the anthers of one flower to the stigma
of the same flower or another flower located on the same plant
...
Agents of pollination of pollination include insect, wind, water, bat, birds etc
...
Bear unisexual flowers either male or female on a plant such as dioecious species
...
Have stigmatic flap on some insect pollinated flowers which can close as the insect
leaves the flower to prevent pollen from reaching the stigma
Anthers and stigmas of the flower mature at different times i
...
protandry (anthers)
and protogyny (stigma)
...
C]racteristics of insect pollinated flowers (entomophilous flowers)
...
Example are hibiscus, bean,
groundnut flower etc
...
T
7) The style is long to expose the stigma
8) Flower is unisexual
...
What are the differences between insect pollinated flowers and wind pollinated flowers?
Fertilization if flowering plants
...
The outer wall or exine burst while the inner wall or intine grows out into a pollen tube which
penetrate the tissues of the stigma, style towards the micropyle
...
This growth is also stimulated
by auxins secreted by the gynoecium and the pollen tube is directed towards the ovary by
107
chemical attraction which is an example of positive chemotropism
...
A larger nucleus called the tube
nucleus and a smaller one called the generative nucleus
...
The role of the tube
nucleus is to control growth of the pollen tube while the generative nucleus follows behind
...
The function of the pollen
tube is to transport the two male gametes to the embryo sac of the ovule
...
e
...
One of the male gametes fuses with the egg to a zygote while
the other fuses with the polar or definitive nucleus to form the primary endosperm nucleus
...
Usually more than one ovule is
present in the ovary of some species thus must be fertilised by a separate pollen grain if it is
to become a seed
...
The synergids and antipodal cells disappear soon after
fertilization
...
The primary endosperm nucleus also divides repeatedly to form the nutritive
endosperm
...
The endosperm may persist as food storage tissue in some seed like cereals such
as maize, wheat etc
...
In this case, the
cotyledons take over the function of food storage while the micropyle persist as a small hole
in the seed through which water is absorbed during germination
...
After fertilisation, the corolla, calyx, style, stigma and stamen wither and fall off leaving only
the ovary
...
In
some flowers, the calyx may remain attached to the fruit but in a dried form such as in guava
and tomatoes
...
109
Title: Micro Molecules
Description: These notes give an overview about the structure of micro molecules. These notes are suitable for High school and undergraduate students
Description: These notes give an overview about the structure of micro molecules. These notes are suitable for High school and undergraduate students