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Respiratory system
Respiration: oxidation of carbs and fats to release energy
Gas exchange: swapping one gas for another
Ventilation: movement of gas in and out of a space within an
organism
Breathing: ventilation in the lungs

Inhalation
1
...

3
...

5
...


Diaphragm muscles contract  diaphragm flattens
External intercostal muscles contract  ribcage moves up and out
Volumes of lungs increases
Pressure in lungs decreases
Air enters lungs to equalize pressure
Alveoli interior walls coated with surfactant – prevents walls from sticking
together

Exhalation
1
...

3
...

5
...


Diaphragm muscles relax  diaphragm domes up
Internal intercostal muscles contract (2 ins make an out)  ribcage moves down and in
Volume of lungs decreases
Alveoli walls are elastic so also contract
Pressure in lungs increases (v
...
04%
o Others (including H2O): ~1%
CO2 rich/O2 poor blood flows from heart to lungs via pulmonary artery
In lungs pulmonary artery divides to form millions of capillaries that cover the surface of
the alveoli
As you breathe in (relatively) CO2 poor/O2 rich air flows into alveoli
Gases diffuse down concentration gradients, therefore:
o CO2 leaves blood and O2 enters blood
o Capillaries rejoin to form pulmonary vein

Adaptations of the alveoli
The alveoli are adapted to increasing the rate of diffusion
Fick’s law states:
o Rate of diffusion = (surface area x concentration gradient/distance)
Alveoli are adapted to increase surface area and concentration gradient and to decrease
distance
Thin walls of alveoli and blood vessels (small cells)
Capillaries and alveoli are very close
Millions of alveoli
Alveoli are very small
Alveoli are spherical
We breathe 15 times a minute
There is a constant blood flow
Millions of capillaries

Capillaries are very narrow

What happens to the O2 when it gets into the blood
Diffuses into red blood cell RBC and binds into haemoglobin Hb
Each Hb has 4 subunits
2 α and β globin (globular protein chain)
Each subunit has 1 haem group (prosthetic = non protein)
Each haem contains 1 Fe2+ ion
Each Hb can absorb 8 oxygen atoms
Oxygen molecules have to pass through 5 membranes before being absorbed by Hb

Respiration

The main metabolic pathway in cells (chain of enzyme controlled chemical reactions)
Controlled release of energy from organic molecules e
...
glucose
A series of oxidation reactions (i
...
adding oxygen) to form CO2 and H2O
The usual respiration substrate is glucose
C6H12O6 + 6O2  6CO2 + 6H2O
But we also have the ability to respire fats (and proteins – but only if we are starving)
Chemical energy in glucose transferred to ATP (adenosine triphosphate) – the universal
energy currency to be made available for all other cellular processes
ATP = adenosine triphosphate: adenine + ribose = adenosine
o The universal energy currency
 Used in all cells
 Used for a variety of purposes
 Continually recycled
 Small and easily transported within cells
o ATP synthesized during respiration and used in most other reactions
o

Where does aerobic respiration take place?
Aerobic respiration is actually a 2 step process
In the first step (6C) is split into 2 molecules of pyruvate (3C) (+2xATP) called glycolysis
This occurs in the cytoplasm
The pyruvate diffuses (facilitated) into the mitochondria
In the mitochondria pyruvate is completely oxidized to form CO2 and H2O
Which is when most of the ATP (32 mol) is synthesized
Both processes are multi-step enzyme-controlled reactions

Three reactions in respiration:
Phosphorylation: kinase
Decarboxylation: decarboxylase
Dehydrogenation: dehydrogenase
Aerobic Respiration occurs in 5 steps:
1
...
Occurs in cytoplasm
b
...
Facilitated diffusion
a
...
Link reaction
a
...
Krebs cycle

a
...
Oxidative phosphorylation
a
...
Forms H2O and most ATP (32)

Glycolysis
Phosphorylation/Glucose activation
o Glucose  Fructose 1-6 BisPhosphate (from ATP)

Fru BP

Glc
TP
Energy level
Pyr

Nicotinamide adenine dinucleotide
Nicotinamide group accepts H+ and e- to become reduced
If nicotinamide is replaced with flavin it is called flavin adenine dinucleotide (FAD)
Can be additionally substituted with an extra P in which case it is called nicotinamide
adenine dinucleotide phosphate – NADP
(nicotinamide derived from nicotinic acid = niacin = vitamin B3)
NAD+ readily and reversibly binds with H+
The enzyme dehydrogenase removes H+ from one molecule and transfers them to
NAD+
NAD+ is therefore reduced to NADH (and the substrate oxidized)
REDOX reactions
o The complete reaction can be written as:
 NAD+ + 2H+ + 2e-  NADH + H+
o NAD+ is therefore called a H+ carrier molecule as it is able to move H+ around the
cell

Mitochondria

Link reaction
Occurs in matrix of mitochondria
Pyruvate
Add coenzyme A

Acetyl CoA

One carbon is lost, oxidation of carbon
Reduction of NAD+

Krebs Cycle

Glycolysis
Link
Krebs
Total

ATP
2
2
4

NADH
4
2
6 (+2 FADH2)
12 (+2)

CO2
2
4
6

Product
2 x pyruvate
2 x acetyl CoA
-

Digestion
1
...
The process of taking food into the body though the mouth
2
...
The process of breaking down food by mechanical and enzymatic action
3
...
The process of absorbing substances into cells or across tissues
4
...
The conversion of nutrients into a usable form
5
...
The process of discharging undigested food as faeces

How molecules are digested
Chemically
o Enzymes
o HCl
Physical
o Mastication
o Bile
o Peristalsis

o
Enzyme
Carbohydrases:

Substrate

Products

Amylase
Maltase
Sucrase
Lactase

Amylose
Maltose
sucrose
lactose

Lipase

lipids

Maltose, glucose
glucose
Fructose, glucose
Galactose and
glucose
3 fatty acid
molecules and
glycerol

Proteases:
Pepsin
Endopeptidase
Exopeptidase
Dipeptidase

proteins
polypeptides
Proteins and
polypeptides
Dipeptides

Nuclease

DNA

polypeptides
Amino acids
Polypeptides and
amino acids
Polypeptides and
amino acids
nucleotides

Location
Small intestines,
mouth, pancreas
Saliva
Intestinal juice
Small intestine
Villi
Pancreas, mouth

Stomach
Stomach
Stomach
Stomach
pancreas

Cross section of digestive system
The wall of the alimentary canal is made of 4 layers of tissue:
 (lumen)
1
...
Submucosa
3
...
Peritoneum

Stomach
1
...

3
...

5
...

7
...


food bolus enters stomach
cardiac sphincter closes
peristalsis churns food
goblet cells secrete alkaline mucus, parietal cells secrete HCl, chief cells secrete
pepsinogen
in the acid of the stomach, pepsinogen (inactive)  pepsin (active) by removal of short
amino acid segment and alteration to form active site
pyloric sphincter opens
chime passes into small intestine
(about 2
...
bile salts
Causes emulsification of lipids
Increased surface area for increased lipase action
Also contains bilirubin (bile pigments)
Also contain cholesterol
Too much  gall stones
Bile DOES NOT contain enzymes
Made in liver
Stored and concentrated in gall bladder

Absorption
Digestion products (monosaccharide, simple sugars, amino acids, fatty acids, glycerol) and
other materials pass into circul
...
as possible reabsorbed
o Leaving semi-solid faeces

Cardiovascular system
Structure of the heart
Double circulation
o Pulmonary system incl
...
aorta, vena cava and all arteries and veins + left side of the
heart
Muscle
o Cardiac muscle: does not tire, cannot respire anaerobically or anything but
glucose
o Myogenic: contracts by itself i
...
not controlled by nerves
o Blood supply: 2 coronary arteries branch from aorta, provide O2 + glucose etc
...

10% bound to
proteins inclu Hb
...

Hormones
Glands
Antibodies
Blood
Urea
Liver
Heat
Liver and muscles
Erythocyte = red blood cells

To where
Everywhere
Everywhere
Lungs

Target organs
Infected sites
Kidneys
Extremities and skin

In what form
Glucose/amino acids
etc
...
sensory and
motor systems)
PNS
Autonomic NS
Sympathetic NS

Somatic NS

Parasympathetic NS

The Neurone
Specialised to carry electrical impulses around the body
Classed according to function:
o Sensory neurone
 Carry impulse from receptor to relay or
motor
 1 Dendron, 1 axon
o Relay neurone
 Carry impulse between neurones
 Many short dendrites
o Motor neurone
 Carry impulse to relay or sensory to effector
 Many dendrites, 1 axon
 Dendrons
o Small extensions of cell body that divide to form dendrites
and carry impulse to cell body
 Cell body
o Contains nucleus and lots of ER (endoplasmic reticulum)
 Production of neurotransmitters
 Axon
o Single, long fibre: carries impulse away from cell body
 Motor end plate
o Connects directly to muscle
Myelinated neurones
o Some fibres are wrapped in Schwann Cells
o Protect and insulate fibre (therefore, impulse travels faster), also phagocytic and
repair damaged peripheral neurones
o Schwann cell membranes are rich in myelin
o Therefore called the myelin sheath
o Between each Schwann cell there is a gap ~2
...
g
...
Threshold value of
receptor exceeded a “generator potential” established
 Sensory neurone = generator potential leads to “action potential”
along neurone
 Relay neurone = within spinal cord
...

 For every 2 K+ pumped into the cell 2 Na+ are pumped out
o Facilitated diffusion of K+ back out of the cell
So there is a build-up of Na+ outside the cell
A build-up of K+ outside the cell, some of which diffuse out of the cell
Generating overall a greater concentration of +ve charge ions outside the cell
THERE IS ALSO SOME DIFFUSION OF Na+ BACK INTO THE CELL BUT NOT MUCH

Na+

K

+

K+

K+ Concentration gradient

Na

Na+ Concentration gradient

+

K+

+ve ion concentration gradient



+ve charge
More Na+ and K+
-ve charge
Less Na+ and K+

K+

Plasma membrane
Na-K co-transporter protein
Pumps 2 K+ into cell
Pumps 3 Na+ out of cell
Requires ATP

K channel protein
Allows diffusion of K+ out of
cell

Action potential

When an impulse passes down a neurone the resting potential is rapidly but temporarily
changed to an action potential
the “localized imbalance of ions across the axon membrane” so that there is a +ve
charge inside and a –ve charge on the outside of the cell
the reversal of the charge during the action potential is called depolarization
the depolarization of one section causes the depolarization of the next so that the action
potential moves down the neurone – a nerve impulse
Initiating action potential
1
...
Na voltage gates open (i
...
respond to changes in potential difference)
3
...
–ve charge inside cell decreases
5
...
Na gates shut and the K voltage gates open
7
...
Causing inside of cell to become –ve again – repolarization
9
...
K voltage gates shut
11
...

There are two types of NT – inhibitory or excitatory
Many drugs block (inhibitors) or mimic (analogues) NT e
...

cocaine, cannabis, paracetamol, beta-blockers etc
...
g
...

2
...

4
...


Protection
Support
Movement
Mineral store
Blood production

Joints
Joint = where 2 bones meet
Types of joint:
Ball and socket (shoulder)
Hinge (elbow)
Rotating (neck)
Sliding (foot and hand)
Parts of joint:
Bones – humerus vs
...

Cardiac
o Involuntary
o Only in heart
Skeletal
o Voluntary
o Attached to bones
o Approx
...
Myosin has stalked heads (with ADP bound) + Actin has myosin binding sites
2
...
Ca2+ binds to actin  conformational change allowing myosin to
bind
3
...
At same time ADP released
4
...
As long as Ca2+ is still present cycle repeats itself
6
...
of blood, lymph and tissue fluid
within a narrow range
o Maintenance of constant internal environment
Internal environment is always changing
Homeostasis returns condition to set point (optimum)
There is fluctuation around optimum
Why is homeostasis important?
o Enzymes are pH and temperature sensitive
o Cells are osmotically sensitive
o Biochemical reactions are in equilibrium
o Controlling internal environment means less dependent on external environment
so geographical range increases
Homeostasis relies on feedback
How are the following homeostatically controlled?
Blood pH
Carbon dioxide – lungs
Blood glucose – liver, pancreas
Body temperature – skin, hair
Water balance – kidneys
Control of blood sugar content
The pancreas
o Acts as an endocrine gland and an exocrine gland
 Endocrine: secretion of insulin and glucagon into the blood
 Endocrine tissue is contained in the Islets of Langerhans
o Islets of Langerhans contain:
 α cells: glucagon
 β cells: insulin
 Capillaries
 Exocrine: secretion of pancreatic juice into the digestive system
Why do we need to control the level of blood sugar?
o Maintain osmotic potential of blood
o Brain only metabolises glucose
o Supply and demand not constant
What are normal blood sugar levels?
o 90mg per 100ml
What happens if blood sugar rises above about 180mg per 100ml
o Excreted in urine/less reabsorbed into blood in PCT (proximal convoluted tubule)
Where do we get glucose from?
o Diet
o Breakdown of stores – glycogen
o Other sources – gluconeogenesis – new glucose from amino acids/fats etc
...

 Exercise
 Mental activity



 Growth and repair (cell division)
 Anabolic reaction (macromolecular synthesis)
What happens in blood sugar rises?
o β-cell of the Islets of Langerhans
o Produce insulin
o Every cell in your body has insulin receptors on plasma membrane except red
blood cells
o Binding of insulin increases permeability of cell membrane to glucose
a
...
Activates conversion of glucose  glycogen in liver and muscles
c
...
α-cells produce glucagon
2
...
Activates phosphorylase
4
...

The thermoregulatory centre detects
changes in blood temperature
...
g erythropoietin – stimulates rbc reproduction)
Nephrons
1
...
All small molecules leave blood and form filtrate in Bowman’s Capsule
3
...

4
...

5
...

6
...


Ultrafiltration
1
...

3
...

5
...

7
...
10nm) –
Fenestrated
The basement membrane (layer of collagen connecting the walls of the arterioles with
the walls of the Bowman’s capsule) also have small pores
The walls of the endothelium of the Bowman’s capsule are specially adapted to reduce
the interference – Podocytes
The podocytes maintain the structure whilst allowing filtrate to pass under and between
the cells instead of through them
The renal filtrate
Everything with a molecular weight of about 70,000 will be forced out of the blood into
the renal filtrate including:
o Glucose
o Amino acids
o Mineral ions
o Urea
o Water
In other words everything except:
o Cells
o Platelets
o Large proteins
 Immunoglobins
 Clotting proteins
The filtrate has a similar composition to the blood plasma

Loop of Henle
1
...

3
...

5
...
Wall of collecting duct also permeable to water, therefore osmosis as well
7
...
Sperm duct
2
...
Prostate
4
...
Epididymis
6
...
Scrotum
8
...
Pelvic bone
10
...
Urethra
Semen
Seminal vesicle
o Produces a fructose rich fluid (seminal fluid) that provides sperm with a source of
energy and provide sperm with a medium they can “swim” in
...
Ovary
2
...
Uterus
a
...
Vagina/canal
5
...
Labium majora
7
...
Pelvic bone
9
...
Anus
11
...
Germinal epithelium goes through mitosis to create spermatogonium
Cells migrate
2
...
Primary spermatocyte goes through Meiosis I to produce secondary spermatocyte
of seminiferous
4
...
Spermatids go through differentiation and maturation to produce spermatozoa (mature
sperm)
Spermatozoa
Acrosome:
o Contains enzymes to help reach egg – (3µm x 4µm)
Mid-piece:
o Many mitochondria arranged in spiral, provide ATP for tail – (7µm)
Tail:
o Microtubules (in 9+2 arrangement) like flagella or prokaryotes – (40µm)

Hormonal control of spermatogenesis
Hormone
Where it’s secreted
FSH
Pituitary

LH

Pituitary

Testosterone

Testes (leydig cells in
interstitial spaces)

Effect on testes
Stimulates the germinal
epithelium to begin
spermatogenesis (up to
meiosis II)
Stimulates the leydig cells to
produce testosterone
stimulates the
spermatogenesis to
completion

Ova
Oogenesis
1
...
Oogonium goes through mitosis to produce oocyte (during childhood)
3
...
Secondary oocyte goes through meiosis II to produce ovum (during fertilization)
Ovum

Oocyte
Ovum

Number of gametes

Timing of the
formation of
gametes
Timing of the
release

Polar body

Polar body
Oogenesis
Millions of oogonia formed
Hundreds of thousands of primary
oocytes
Few secondary oocytes
1 ovum per menstrual cycle
Start during pregnancy
Ends during pregnancy
Completed during fertilisation
Ovulation

Fertilization
Vagina is acidic, pH of semen is alkaline
(prostate) to neuralise
Sperm swim to oviduct
Pass through follicle cells
Hydrolytic enzyme of acrosome digest
glycoprotein of zona pellucida causes
capacitation – preparation of sperm
Membrane of head of sperm fuses with oocyte
membrane
As this happens cortical granules release
contents outside oocyte by exocytosis which
prevents more sperm crossing membrane
(cortical reaction)
Also triggers rest of meiosis II (2nd polar body
formed)
Male/female nuclei join – fertilization complete

Spermatogenesis
Millions and millions

All through life from
puberty
During ejaculation/sexual
reproduction

In Vitro Fertilisation (IVF)
Infertility
Causes:
o Blocked oviducts/sperm duct
o Low sperm count
o Surgery/trauma
o Drugs
o Medical disorders
o Genetic/hormonal
o Disease (mumps, gonorrhea)
o Obesity in women
o Endometriosis
o Antibodies produces by the women
Before IVF Cycle:
1
...
Inject high dose of FSH for 1 week
3
...
Eggs removed with big needle (and ultrasound) transvaginally
2
...
Sperm and egg mixed in petri dish
4
...
Next day dishes checked for fertilization
2
...
2 weeks later pregnancy test carried out
4
...
g
...
g Rubella)
No alcohol or drugs (foetal alcohol syndrome)
Process of birth
1
...
Contractions of wall of uterus
3
...
Cervix stretches
5
...
Message to brain
7
...
Muscles contract forcibly
9
...
Birth
11
...
Posterior pituitary stops releasing oxytocin

Data Collection and Processing
Do boys have quicker reaction times than girls?
Collect sufficient data
Display it in suitable tables
Manipulate it (conversions, averages, S
...
and T-test)
Plot a graph (1 bar chart)
Write an evaluation

Cells
How big are cells?
Smallest = bacteria (0
...
5mm)
Most eukaryotic cells (0
...
01mm

SI Units
How do we calculate how big an object is?
The magnification is the number of times bigger the drawing is compared to the actual
object (NB a fraction is a reduction in size)
If you know the magnification you can easily calculate the actual size of the object
Magnification = Size of Image/Actual Size of Object
DO NOT USE CENTIMETRES!
Scale bars:
Give relative length so it is easy to calculate magnification
Imagine a tiny ruler has been places next to the sample
When the sample is magnified so the ruler will be too
Magnification:
The number of times larger the picture is compared to the actual image
Resolution:
How clear an image is; how far apart 2 objects must be before you can see them as 2
separate objects

Prokaryotes
Cells without nuclei
o Or any membrane-bound organelles
o (i
...
no mitochondria, chloroplasts, ER, Golgi)
DNA is free-floating in cell but aggregates to form nucleoid
DNA is normally circular not linear
DNA is naked (no associated proteins) so does not form chromosomes
Main structured features:
Cell wall (not cellulose)
Pili
– for cell adhesion
Flagella – for movement
Ribosomes (70S)
Prokaryote cell division
Bacterial cells divide by binary fission
(not mitosis as no chromosomes)

Eukaryotes
Cells with nuclei (plants, animals, fungi, Protista)
Light vs
...
e
...
lysosomes)
They are all bilayers of phospholipid molecules
o the membrane bilayer is made of 2 layers of phospholipids
o a phospholipid is a modified lipid is a lipid (glycerol + 3 fatty acids) where one of
the fatty acids is replaced with a phosphate group
The functions of membranes are:
Control of entry/exit of material
Recognition (cell - cell/cell - molecule)
Boundary between cell and environment
Isolation of organelles within cells
Internal transport (Endoplasmic reticulum)
Isolation of enzymes (lysosomes)
Provide metabolic surfaces (RER, mesosomes in prokaryotes, crista in mitochondria)

Hydrocarbon tail

Phosphate group

Glycerol

Glycerol

Hydrocarbon tail

Hydrocarbon tail
Hydrocarbon tail

Hydrocarbon tail
A lipid (triglyceride)

Phospholipid

Hydrocarbons are long chains of CH2 and so they are very hydrophobic (“water hating”)
The phosphate has lots of Oxygen and so is highly hydrophilic (“water loving”)
This means they are both soluble and insoluble in water
The phospholipids give the membrane its basic structure as well as its fluid nature (it is
called the fluid mosaic model)
But membranes also have a lot of other molecules attached or embedded in them
included
o Proteins
o Glycoproteins
o Glycolipids
o Cholesterol
These carry out the specific functions of the membrane

Functions of membrane proteins
Hormone binding sites
o
Immobilized enzymes
o
Cell adhesion
o Epithelial cells
Cell–cell communication
o Neurotransmitter
Protein channels
o
Protein pumps

Components of the cell membrane
How do they stay in the membrane?
o The nature of the proteins etc
...
Researchers thought that membranes are mainly made of lipids because lipids would
allow fat-soluble materials to move across the membrane by being dissolved in it
2
...
g
...
e
...
e
...
g
...

Why doesn’t a consumer get 100% of the energy from the plant?
o Animals don’t eat all the plant (bark, roots, flowers)
o Animals excrete some of the plant (fibre)
Carnivores
Why isn’t 100% of the energy a herbivore converts into Biomass made available to the
secondary consumers?
o Herbivores use some of the energy in respiration for growth, cell division, active
transport, heat etc
...


Populations and competition
4 phases of the sigmoid growth curve CLOSED SYSTEM
o Lag phase
 Organisms are adjusting to new environment and a small number of
individuals so reproduction is slow
o The growth (exponential/log) phase
 There is plenty of space and resources (food, water etc
...

o The death/decline phase
 Resources are running out waste products are building up etc
...
What are the main greenhouse gases?
a
...
038%)
b
...
Water vapour
2
...
Industrialisation
b
...
Burning fossil fuels
d
...
Why are they called the greenhouse gases?
a
...
How do we know the concentration of carbon dioxide in the atmosphere 1000s of years
ago?
a
...
Why does the carbon dioxide concentration go up and down by approximately the same
amount each year?
a
...
Why has the carbon dioxide level increased since the 1800s
a
...
What is the link between carbon dioxide levels and global temperatures

Biological indicator species
How do we monitor human impact on environment?
o Direct measurement
 Measure pH, pollutant concentration etc
...
g
...
)
Ergo: shoot bends towards light
Apical dominance
In high concentrations auxin inhibits lateral bud growth
Auxin is synthesized in the apical meristem (tips) and diffuses down the stem
As you move away from the meristem the concentration of auxin decreases
Below a certain concentration of auxin (the threshold) it no longer has an inhibitory effect
- the lateral buds develop
...
If the light is directly overhead, the auxins are evenly spread,
therefore the shoot grows straight up (slowly)
...
If a shoot is grown in the dark, auxins accumulate throughout the
shoot, causing the shoot to grow faster as it would if it were
underground (only works with shoots as they have a store of food)
...
Uptake
A
...
Mass flow - as water is absorbed so hydrostatis pressure arond root decreases,
water (with dissolved minerals) flows towards roots to equalise root
...
Fungal mycorrhiza - a mutualistic relationship, fungus covers much larger area
and absorbs minerals
...
Diffusion - as plant absorbs minerals concentration around root system
decreases, therefore mineral ions diffuse towards root
B
...
Diffusion - some minerals can be absorbed into roots by simple diffusion or
facilitated diffusion as long as the internal concentration is less than the external
concentration
b
...
Important as plant can continue to absorb
nutrients even if external concentration is very low
c
...
Branching
b
...
Mycorrhiza
d
...
of root hairs) have numerous carrier proteins
e
...
Root hairs have extensive RER/Golgi for carrier protein assembly
Movement through root
1
...
Symplastic - diffusion through cytoplasm (and plasmodesmata - holes in cell wall)
3
...
Vascular tissues surrounded by endodermis, therefore water/ions must cross
endodermis to get into xylem
2
...

Prevent apoplastic route so all water diverted through cytoplasm
...
Water/ions enter xylem due to transpiration
...

5
...
Hollow interconnected tubes
2
...
Lignified cell walls
6
...
Transpiration stream - water absorbed from leaves decreases hydrostatic
pressure at top of xylem so water is drawn up xylem
2
...
Transpiration Stream
1
...
Osmotic pressures
3
...
Role of transpiration
1
...
Bring H2O + ions
3
...
Adaptations to reduce transpiration
1
...
Waxy cuticle
3
...
Factors affecting rate of transpiration
Anything that will affect the rate of evaporation will affect the rate of transpiration:
1
...
Temperature
3
...
Humidity
Xerophytes, mesophytes, hydrophytes
Xerophyte: plants adapted to low water environments
Mesophytes: plants adapted to average water environments
Hydrophytes: plants adapted to high water environments

Phloem
Functions of Phloem
Source

Sink

Leaves

Root & shoot Apices

Storage organs

Flowers, Fruits, Seeds etc
...
e
...
Light harvesting
i
...
The light depending reactions
i
...

i
...

Both made up of C, H and O and also N and Mg
A lack of N (nitrates or ammonium) in the soil is the most common cause of plant growth
retardation
Plants lacking in N and/or Mg have yellowish leaves (chlorosis) as they do not produce
sufficient
Photosynthesis occurs in 3 stages
Light harvesting
o Absorption of light energy by the photosynthetic pigments
 Chlorophyll

 Thylakoid
The chloroplasts have pigment molecules are arranged into PHOTOSYSTEMS
2 different photosystems involved in photosynthesis
 Photosystems I and II (PSI & PSII) - both are embedded in the
thylakoid membranes
o The photosystems are made of a variety of pigments and proteins but always
with a chlorophyll molecule at its centre
o The proteins are encoded by the chloroplast DNA
o When light strikes one of the pigments, a pair of electrons are boosted to a
higher energy level
o The ENERGY (not the electrons themselves) is then transferred to the
chlorophyll molecule in the "reaction centre" of the photosynthesis
The light dependent reactions
o Light energy is converted into chemical energy (ATP), water is split (photolysis)
 Photolysis of H2O
 Thylakoid
o Excitation energy of electrons is used to split water (photolysis)
o This generates an H+ ion concentration gradient across the thylakoid membrane
o Which in turn is used to synthesis ATP
o And to reduce NADP+ to NADPH
o (NADPH is very similar to NADH, the only difference is that it has a P which
stands for phosphate)
Non-cyclic electron flow
o The PSII in thylakoid space water is split to form H+ + e- + 1/2 O2
o The protons remain in the thylakoid space
o the electrons are passed down an electron transport chain to PSI
o As they do they pump more H+ across the membrane
o Generates a chemiosmotic potential or electrochemical gradient
o electrons reach PSI and get another energy boost
o Pass to NADP+ reductase
o NADP+ + H+ + e- --> NADPH
o H+ pass through ATPase and generate ATP
o PHOTOPHOSPHORYLATION
Cyclic electron flow
Non-cyclic electron flow
o
o

Only PSI involved

PSI & II involved

Electrons kept in electron transfer chain

Electrons donated by PSII
Electrons accepted by NADP+

ATP formed

ATP formed

No NADPH formed

NADPH formed

Photolysis of water not required

Photolysis of water required

The light independent reactions
o CO2 is reduced to produce sugars and other organic molecules
 Reduction of CO2
 Stroma

Calvin Cycle
The ATP and NADPH are formed during photophosphorylation are then used in the Light
Independent reactions (aka carbon fixation or the carbon cycle)
In the 1940s & 50s Melvin Calvin worked out the process of CO2 fixation in
photosynthesizing green algae
By feeding the algae 14CO2 and at time intervals looking at the products of fixation he
could work out the sequence of events that lead to the formation of complex molecules
...
g
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g
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Cell Division

Why do cells divide?
o To allow us to grow
o To replace old cells
o To repair damaged tissues
o Asexual reproduction
o Formation of gametes in sexual production
o 2 types of cell division

Mitosis
o forms 2 cells
o each new cell (daughter cells) has the same number of chromosomes as the original cell
o Daughter cells are genetically identical to parent
o Used for growth and repair and in asexual reproduction
o Meiosis
o Forms 4 cells
o Each has half the number of chromosomes as the parent (haploid cells)
o Daughter cells are different to parents
Nuclear Organisation
o

Nucleus

o

Nuclear envelope/membrane

o

Nuclear pore

o

Nucleolus

o

Chromatin


Heterochromatin

 Euchromatin
Chromosome Structure
o Chromosome
o Chromatid
o Centromere
o Telomere
o Karyotype
o Homologous pairs
o DNA with same sequence of genes
o Sister chromatids
Karyotype
o During prophase or metaphase take a picture of the nucleus
o Cut up the chromosomes and arrange them into pairs
o Used for


sex determination



Identifying chromosome abnormalities


Down's syndrome



Klinefelter's syndrome



Turner's syndrome etc
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Natural classification

Analogous characteristics
Same function
E
...
bat wing, butterfly wing, beetle wing, bird wing, flying fox “wing”, flying fish “wing”
Artificial classification

Linaean binomial classification system
Swedish botanist (1707 – 1778)
All organisms given 2 names – generic name (genus) and specific name (species)
There then collected together into bigger and bigger groups (taxa)
Taxonomy – Study of classification
Kingdom
Animalia
Phylum
Chordata
Class
Mammalia
Order
Primate
Family
Hominidae
Genus
Homo
Species
sapiens

RULES!
Genus and species always in italics (or underlined)
Genus always has a capital letter, species is lower case
First time you use it you must spell it out in full (e
...
Homo sapiens) but second time can
abbreviate genus (e
...
H
...
coli
If you don’t know the species, just write the genus and then sp (e
...
H
...
g
...
spp)

Need to know characteristics of:
Bryophytes
Filicinophytes
Coniferophytes
Angiospermophytes
Porifera
Cnidaria
Platyhelminthes
Nematodes
Molluscs
Arthropods
Plants
Animals
Viruses
Fungi
Protists

Evolution
The change in organisms over millions of years due to the accumulative of many small changes
driven by natural selection
Some more important terms:
Reproductive success
o Passing on genes to the next generation so that they too can then pass on
Speciation
o Formation of a new species
Selection pressure
o Anything that reduces the chances of reproductive success
Notes:
Organisms evolve from common ancestors that split to create different species – speciation by
divergence
Frequently occurs due to separation of species geographically and so populations subsequently
subjected to different

Evidence for evolution:
Comes from four main sources:
o Fossils
o Selective breeding
o Homology & ontogeny
o Genetics and genomes
Fossilisation
o Petrification (replacement w/ silica)
o Structures (coral)
o Preservation (amber/ice)
o Direct (shells)
o Impressions (footprints/leaves)
o Faeces (coprolite)
o Very rare event
o Requires specific conditions
o Fossils have to be found
o Only animals (& plants) that live in those environments can be fossilised
o So only get limited view of evolution
o Fossil record is not nearly complete
o Dating fossils is hard
Artificial selection
o Large changes can be induced in species over relatively few generations:
 Cows
 Dogs
 Pigeons
Homology and Ontogeny
o Homology
 Structures with same evolutionary origins but different functions
 E
...
pentadactyl limb
o Ontogeny
 Development
Genetics and genomes
o All living things on the planet use the same genetic code
o Closely related species have fewer differences in genome than more distantly related
species
o Gene sequences also show similarities/differences based on evolutionary descent
Evolution in action
How does Natural Selection fit with evolution?
Explain how antibiotic resistance has developed in bacteria?
Bacteria has adapted to be resistant against antibiotics because a mutation arose in bacteria
causing the ones with the mutation to survive and the others to die out, meaning that it is
passed down through generations
...
What is the full classification of humans?
1
...
Phylum: Chordata
3
...
Order: Primates
i
...
Family: Hominidae
i
...
e
...
Morphology = bipedalism – just man

iii
...
Genus: Homo
i
...
Species: sapiens
2
...
The fossil record is incomplete
2
...
e
...
The molecular clocks and fossils may give conflicting data
4
...
g
...
Victorian – struggle
ii
...
Between wars – tools
iv
...
Post war – hunter-gatherers
vi
...
70s – woman the gatherer
viii
...
Ardipithecus ramidus
i
...
Walked upright
iii
...
Brain 300cc
b
...
2mya
ii
...
Less pronounced brow-ridge
iv
...
Australopithecus afarensis
i
...
More slender and gracile
iii
...
Homo habilus
i
...
Less protruding face
iii
...
Evidence of tool use
v
...
Homo erectus
i
...
Brain 850-1100s (overlaps with modern man)
f
...
0
...
More heavily built/robust and stronger
iii
...
Brain 1500cc

Dating Fossils
Age of rocks
o Geologists have a good idea of the age of different types of rocks
...
e

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