Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

STRUCTURAL ORGANISATION OF A CELL

1
...
Surface: volume
ratio decreases with increasing size of cell
...



2
...



3
...
g
...
Nerve cells are large as they are able to conduct impulses
...


Cells regulate their activities by flow of energy and flow of extrinsic and
intrinsic (genetic) information
...


Green cells trap radiant solar energy and convert it into chemical
(potential) energy like ATP which on oxidation of food is converted into
kinetic energy for doing work
...


Schwann (1839) recognized that animal and plant cells are alike except
that animal cells lack cell wall
...
Rudolf virchow (1855) was first to
modify cell theory and gave generalization- “Omnis cellula e cellula”
...
The specialized cells lose some of
their autonomous activities, e
...
, muscle and nerve cells do not divide and
RBCs do not respire
...


Cells show 3 types of organization:

...


(b)  Eukaryotic cell
...
52; two envelop system, membrane bound
organelles; histone and true nucleus present
...


8
...
g
...
Size 0
...
88; only one envelope
system; membrane bound organelles absent; histone, nuclear
membrane, nucleolus, cyclosis meiosis absent
...
g
...



Cell organelles (organoids) are of four types on the basis of membranes
...



...
g
...



...
g
...



...


(i)  Organelle bounded by single unit membrane
...
g
...


(iv)  Organelle without any membrane e
...
, Ribosomes, centriole,
nucleolus
...


(i) Rotation (cytoplasm moves around a vacuole in one direction) e
...
, Hydrilla leaf
cells
...
g
...
These movements are due to
colloidal nature of cytoplasm and microfilament activities
...


Ribosomes :

...
Robinson and Brown discovered them
first in plant cell
...



...

Proteins synthesized on bound ribosomes are used outside the cell
or incorporated into membrane or go out as secretory (export)
protein
...


(c)  They are smallest, membraneless organelle and are called ribonucleoprotein or Palade particles
...
Their size is 150 to 250 A
...
A ribosome may be 70 S or 80 S
...
70 S are found in both prokaryotic and eukaryotic cells &
lie freely in cytoplasm as in prokaryotes
...
Ergasomes or polyribosomes (Rich
...
A
70 S ribosome has three molecules of rRNA (16 S, 5 S, 23 S) and 53
protein molecules and 80 S ribosome has 3 molecules of rRNA (18 S,
5 S, and 28 S) and 80 molecules of protein
...
Endoplasmic reticulum (Ergastoplasm) : It was reported by Porter, Claude
and Fullman (1945)
...
In muscles, it is called sarcoplasmic reticulum, in eyes called
myeloid bodies and in nerves as Nissle granules
...
GERL
(Golgi associated with ER from which lysosomes arise) system is formed
by ER and golgi bodies and form lysosomes
...
RER arises from nuclear membrane
...
SER consists of tubules mainly
...
SER helps to
synthesize lipids and helps in detoxification
...
Plastids: They are double walled DNA containing largest organelle in plant
cells, discovered by Haeckel (1865)
...
Three types of plastids are (i) Leucoplasts:
Largest, colourless, found in unexposed parts and store starch (amyloplast),

fat (claioplast) or Protein (aleuronplast)
...
(iii) Chloroplasts: Green plastids discovered by Sachs (1862) but
named Chloroplast by Schimper (1885) store starch temporarily; shape
variable, maximum variation in shape is found in green algae
...
Its matrix
(stroma) has prokaryotic naked circular DNA (0
...
50% of matrix is filled with Rubisco enzyme
...

Inner membrane of thylakoid bears quantasomes (functional unit of
chloroplast, discovered by Park and Biggins (1962), size 180 × 150 × 100 Å,
called photosynthetic units (PSU) where primary act of photosynthesis (i
...

release of e–) occurs
...
One of the molecules
of Chl a acts as reaction (trap) centre
...

Two grana are joined by Frets channel (stroma lamella)
...
DNA containing, semiautonomous,
double walled organelles and called cell within cell because they have
their own protein machinery and show cytoplasmic inheritance
...

Chl a is C55 H72 O5 N4 Mg–blue green and has–CH3 group
...

Pyrenoid is a proteinaceous body around which starch is stored in green algae
...

Golgi bodies: Also called as (Lipochondria, Idiosome or Dalton complex):
They are middle man of cell and discovered by Camello Golgi (1898) in cytoplasm
of nerve cell of owl and cat by silver metallic impregnation technique
...
Dalton and Felix (1954) observed them under TEM
and confirmed their existence
...
In fungi, a dictyosome is unicisternal
...
A dictyosome has a stack of usually 3- 12
cisternae with swollen ends, tubules and vesicles
...
Concave or
maturing (M) face or trans face is near cell membrane and cis or convex or forming

(F) face is towards nuclear membrane
...
New cisternae are formed from SER
...
They process package and help in transport and release of secretory
proteins
...
Golgi body forms acrosome in sperm, yolk
and cortical granules in eggs, secretion of insulin, lactoprotein in mammary
glands, cellulose, hemicellulose, mucilage, pectin, cell plate during cell division,
root hairs etc
...
All secretory cells are rich in
golgi bodies
...
These bodies
arise from SER mainly
...
These are double walled, DNA containing, self replicating,
semiautonomous, organelle found only in eukaryotic aerobic cells (except
mature RBC), first observed in insect striated muscles as granular structure by
Kolliker (1850)
...

Altman (1890) studied them in detail and called them as bioplasts
...
Flemming called them file and term
‘mitochondria’ was used by Benda (1897) who stained them with Janus green B (a
vital stain); size 1 = 10 × 0
...

A mitochondrion has two chambers and two membranes
...
(Fernandez and Moranparticles)
...

Inner chamber has a double stranded, naked circular 5 long prokaryotic DNA
with high G-C ratio, 70S ribosomes, RNA and 70 types of enzymes
...
This DNA is 1% of total DNA of cell
and discovered by Nass (1966)
...
Mitochondria are called cell within cell
...
Microbodies : These are (lysosomes, sphaerosomes, glyoxysomes and
peroxisomes): They are smallest single membrane bounded organelle
...
2-0
...
They are common in WBC, liver, spleen etc
...
Novikoff (1956) observed them under
TEM
...
They are of four types: (i) Primary
lysosomes (Storage granules) have inactive enzymes; (ii) Secondary lysosomes
(Heterophagosomes or Digestive vacuoles or Phagolysosomes) cause digestion
(Heterophagy); (iii) Tertiary lysosomes (Residual bodies or Telolysosomes) removes
wastes by ephagy from cell by acting as scavenger or disposal unit; (iv)
Autophagic vacuoles (Cytolysosome or Autophagosomes) are complex lysosomes and
digest old / injured / dead cells and tissues to keep cell healthy (autolysis or
autodigestion)
...
Autophagy is digestion of stored food
(glycogens, fat and proteins) during starvation to provide energy
...
If lysosomes burst and release their
enzymes, the entire cell is digested and liquefied
...

Osteoclasts (which digest bones) are rich in lysosomes; Plant cells lack lysosomes
except Neurospora, root tip of maize, yeast and seeds of pea and cotton
...
They are also involved with diseases such
as Tay-Sachs Syndrome and Rheumatic Arthritis (An Autoimmune
disease)
...


(a)  Sogaerisines (Plant lysosomes) are micro bodies filled with hydrolytic
enzymes for fat synthesis
...
These are
abundant in endosperm of oily seeds
...


(b)  Transosomes are triple layer bounded organelle in ovary follicle cells of
birds to help in yolk formation
...


(c)  Lomasomes are boder bodies between cell wall and cell membrane,
common in fungi, discovered by Moore and Mc Allister (1961) and help in
cell proliferation and elongation for diffusion of substances required in
cell wall formation
...
Catalase and peroxidase are largest and smallest enzymes found in
peroxisomes
...
In
animals they take part in lipid synthesis (b-oxidation of fatty acids)
...
These are common
in germinating oil seeds of castor, groundnut and cucumbers and disappear
after germination
...
The complex is called
centrosome or central apparatus
...
Thus show 9 ÷ 0 organisation
...
Centrioles are required to form basal bodies, cilia,
flagella and spindle poles
...
g
...
Centriole is rich in tubulin, ATP
...

Basal bodies or basal granules or blepharoplasts are microcylinders that lie
below the plasmalemma at the base of flagella and cilia
...

Cilia and flagella: They are microtubular vibratile propoplasmic processes
studied by Engleman and have four parts: basal body, rootlets, basal plate and
shaft
...
Axoneme has nine peripheral doublet fibrils
and two central singlet fibrils
...
All the
peripheral doublet fibrils are interconnected by C-A linkers of protein nexin
...
The
central fibrils and side arms of subfibre A are made of dyenin protein with ATPase activity
...

Vacuoles : Vacuoles in plants were reported by Spallanzani
...

(a) Sap vacuoles: They enclose sap or water with dissolved inorganic and organic
substances
...
Animal cells
have numerous small sap vacuoles that maintain osmotic pressure
...

(b) Contractile vacuoles: They occur in some simple fresh water forms (e
...
,
Amoeba, Paramecium, Chlamydomonas)
...

Contractile vacuoles perform osmoregulation and excretion
...
Gas vacuoles
store metabolic gases and take part in buoyancy regulation
...
Nucleus: A cell may be uni or multinucleated
...
g
...
g
...
Nucleus was reported
by Robert Brown (1831) in orchid cells
...
Hertwig and van Beneden showed the
role of nucleus in fertilization
...
1/10th of volume of cell is occupied
by nucleus
...

Nucleocytoplasmic index is Volume of nucleus/ (Volume of cell – Volume of
nucleus)
...
Nucleus has
80% proteins (65% non histone, Mol
...
high, rich in tyrosine and tryptophan,
acidic and forms enzymes and helps in RNA transaction
...
Wt
...
DNA : histone
ratio 1 : 1
...
Term was given by
Outdet
...
H1 histone does not form
nucleosome
...
5 to 32
...
g
...
Maximum number is 2n = 1262 in Adder’s
fern (Ophioglossuin)
...
And
maximum number is 2n = 1600 in Aulacantha and Radiolarians
...
Giant Chromosomes are: (i) Salivary gland chromosomes (size 2000 m) (ii)
lampbrush chromosomes (size 5900 m)
...

25
...
Nucleolus was discovered by
Fontana (1781), described by Wagner and numbed by Bowman
...


26
...


(a)  Reserve food materials: It can be starch as in plant cells, glycogen
as in animal cells and fungi, fat or aleurone grains (protein rich,
found as outermost layer of cells or endosperms or cereal grains)
...
Crystalloid contains nitrogen as
amides
...



...
They get accumulated in bark, old leaves, vacuoles and
flowers e
...
, alkaloids (Quinine, Atropine, Canada Balsam: a
mounting agent from Abies stem), gums, organic acids, cow milk,
latex from Cow tree (Brosimum) and mineral crystals
...
Cytoskeltal structures: These are fibrous or fine tubular structures which form the
supportive structures of the cell
...


(a)  Microtubules discovered by Robertis and Franchi, (1953) term coined by
Slautterback (1963), are unbranched hollow non contractile tubules of
indefinite length, 25 nm in thickness with 15 nm core and formed of 13
helically arranged protofilaments of a and b-tubilin protein
...
Microtubules are basic structures of
spindle apparatus, centrioles, basal bodies, cilia and flagella and are
responsible for cell motility and maintenance of shape
...
GTP, Ca2+, Mg2+ and a calmodulin bound
protein are required for assembly
...
Microtubules
are basic structures of spindle apparatus, centrioles, basal bodies, cilia
and flagella
...
Microtubules present in
cytoplasm provide shape and polarity to cells
...




...
Microfilaments
can form hexagonal bundles, take part in cytoplasmic streaming,
membrane undulations, cleavage, contraction of muscles, movement of
microvilli to absorb food and endocytosis
...


(c)  Intermediate Filaments are intermediate in size having diameter
around 10- 15 nm and are composed of non-contractile proteins
...
, desmin filaments,
vimentin filaments, synemin filaments)

---