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BIOLOGY PAPER 5 PROCESSES
TOPIC 7:
7A: Glycolysis in the Cytoplasm:
1
...
OXIDATION OF TRIOSE PHOSPHATE:
- After triose phosphate loses hydrogen, it forms 2 x pyruvate
- Hydrogen ions are collected by NAD⁻ which reduces the coenzyme
- Forms 2 x NADH
3
...
2 x pyruvate goes from the cytoplasm and into the mitochondria through the
mitochondrial matrix
2
...
The 2 Carbon compound joins with coenzyme A to form acetyl coenzyme A
- Pyruvate is oxidised
- Loses a hydrogen ion to NAD⁻ & forms NADH through
dehydrogenation
4
...
PRODUCTS OF THE LINK REACTION:

-

Every molecule of glucose produces 2 x pyruvate, so the cycle occurs twice
per glucose molecule
SO, THE PRODUCTS ARE:
- 2 x acetyl CoA
- Energy from here is used in the Krebs Cycle
-

2 x CO₂
2 x NADH
- Used in the Electron Transport Chain to produce ATP

7A: The Krebs Cycle in the Mitochondrial Matrix:
1
...
The 6 Carbon compound is highly unstable so it breaks down to form a 4 Carbon
compound
- 2 x CO₂ is removed in the process & is released as a waste product through
decarboxylation
3
...
The 6 Carbon compound releases Hydrogen atoms that reduces NAD⁻ & FADH⁻²
to 3 x NADH & 1 x FADH₂
5
...
PRODUCTS OF KREBS CYCLE:
- Every molecule of glucose produces 2 x acetyl coenzyme A molecules, so
the cycle occurs twice per glucose molecule
- SO, THE PRODUCTS ARE:
- 2 x ATP
- 6 x NADH
- Used in oxidative phosphorylation
-

2 X FADH₂
- Used in oxidative phosphorylation

-

4 x CO₂

7A: The Electron Transport Chain in the Inner Mitochondrial Membranes:
1
...
E⁻ are carried from 1 electron carrier to another through a series of redox
reactions
3
...
H⁺ ions diffuse into the mitochondrial matrix (through pores on stalked
particles) down the electrochemical gradient
- Energy from here drives ATP synthesis
5
...
Hydrogen atoms are produced from H⁺ & e⁻
- 2 x Hydrogen atoms combine with ½ O₂ to form 1 x H₂O

7A: Number of ATP Molecules Produced During Aerobic Respiration Per
Glucose Molecule:
-

3 x ATP is produced for every NADH molecule
2 x ATP is produced for every FADH₂ molecule

STAGE OF AEROBIC
RESPIRATION

MOLECULE PRODUCED

NUMBER OF ATP
MOLECULES PRODUCED

GLYCOLYSIS

2 x ATP

2

GLYCOLYSIS

2 x NADH

6

LINK REACTION (x2)

2 x NADH

6

KREBS CYCLE (x2)

2 x ATP

2

KREBS CYCLE (x2)

6 x NADH

18

KREBS CYCLE (x2)

2 x FADH₂

4

TOTAL ATP MOLECULES

38

7A: Anaerobic Respiration in Mammals:
1
...
PROCESSING LACTATE:
- Lactate is oxidised back to pyruvate when in the liver
- It moves through the blood
- Causes pH to fall
- Muscle tissue becomes acidic
3
...
Pyruvate goes back to the Krebs Cycle to be respired anaerobically

7A: Anaerobic Respiration in Plants & Fungi:
-

Yeast respires anaerobically to produce CO₂ + ethanol as waste products
Plants respire anaerobically in root cells & waterlogged soil
- Waste products are also CO₂ + ethanol

7A: Actin-Myosin Interactions: Ratchet Mechanisms:
FOR THE CONTRACTION OF MYOFIBRILS:
1
...
Myosin changes shape with its head dipping forward with the help of Ca²⁺ ions
that bind to troponin
3
...
Sarcomeres & muscles shorten
5
...
If the contraction cycle doesn’t repeat, Ca²⁺ ions are pumped back into the
sarcoplasmic reticulum using ATP
- Troponin & tropomyosin return to their original positions & contraction
is complete
- Muscle fibres relax

7A:Stages in the Cardiac Cycle:
1
...
The excitation spreads to the atrioventricular node (AVN)
3
...
Purkyne tissue conducts the wave of excitation
5
...
SYSTOLE

-

THE “QRS” COMPLEX:
- Depolarisation of ventricles leads to ventricular contraction
- AKA
...
DIASTOLE

7A: Calculating Cardiac Output:

HEART RATE X STROKE VOLUME = CARDIAC OUTPUT

1
...
SUBSTITUTE VALUES AND WORK OUT THE MISSING VALUE

7A: Negative Feedback Steps:
1
...
Receptor sends information through the nervous to the central control in the
brain or spinal cord
3
...
The factor/stimulus is continuously monitored by receptors so it fluctuates
around a set value or an ideal value

7A: How Heart Rate Adjusts:
1
...
The cardiovascular control centre responds by sending impulses to the heart
along the sympathetic and parasympathetic nerves
3
...

2
...

4
...
Blood pressure increases as the heart pumps harder & faster than it needs to
- Baroreceptors stretch
2
...
The cardiovascular control centre sends impulses through the parasympathetic
system to slow the heart rate & causes vasodilation
4
...
Sends impulses along sensory neurones to the cardiovascular control centre in
the medulla oblongata
2
...
The heart rate increases as more blood flows to the lungs; more CO₂ is removed
from the blood
4
...
Chemoreceptors respond by reducing the number of impulses to cardiovascular
control centre
6
...
This reduces the acceleration of the heart rate
- Returns back to the intrinsic rhythm

7A: Hormonal Control of the Heart Using Adrenaline:
WHEN STRESSED:
1
...
Adrenaline is carried around the body in the blood & binds to receptors in target
organs, including the sinoatrial node
3
...
This has a direct effect on the sinoatrial node by increasing the frequency of
excitation
- This causes heart rate increase

7A: Control & Regulation of Breathing:
FOR INHALATION: CONTROLLED BY INSPIRATORY CENTRE IN THE MEDULLA
OBLONGATA:
1
...
These muscles contract & cause the volume of the chest to increase
- This lowers the air pressure in the lungs to slightly below atmospheric
pressure
3
...
Due to the pressure difference in the lungs & the air outside, air will flow into the
lungs
5
...
Nerve impulses are sent back to the medulla oblongata which inhibits the
inspiratory centre
FOR EXHALATION: EXPIRATORY CENTRE IS NO LONGER INHIBITED:
1
...
These muscles relax & cause chest volume to decrease
- This increases the air pressure in the lungs to slightly above atmospheric
pressure
3
...
As the lungs deflate, the stretch receptors become inactive
- The inspiratory centre is no longer inhibited & the next breathing cycle
begins

7A: Effect of Exercise on Breathing:
1
...
Increase in H⁺ concentration will decrease blood pH
- Making it more acidic
3
...
Once stimulated, a nerve impulse is sent to the medulla oblongata
5
...
This results in more O₂ entering the lungs & blood stream, while more CO₂ is
exhaled & removed from the bloodstream
- This decrease in CO₂ will result in blood pH returning back to normal
- Leads to normal breathing rate

7A: Releasing A Second Messenger: Ways Hormones Have Their Effects:
PEPTIDE & PROTEIN HORMONES (EG
...
The hormone binds to a receptor in the cell membrane
- This starts a series of membrane-bound reactions that results in the
formation of a second chemical messenger inside the cell
2
...
These changes cause a number of responses in the cell
- Including:
- Increased cellular respiration
- Increased contraction of muscle cells, etc
...
OESTROGEN & TESTOSTERONE) ARE SOLUBLE IN LIPIDS SO
THEY CAN CROSS CELL-MEMBRANES:
1
...
Inside the cell, the hormone binds to a receptor
3
...
The hormone attached to the receptor acts as a DNA transcription factor
- Regulates gene expression & switching sections of DNA “on” & “off”

7A: The Liver & The Deamination Process:
1
...
They remove the amino group & convert it into toxic ammonia & then to a less
toxic urea
- It is then excreted by the kidneys
3
...
The remainder of the amino acids are they used in aerobic, at the beginning of
the Krebs Cycle

7A: Ultrafiltration: A Passive Process:
1
...
The high pressure forces small molecules in the blood out of the capillaries of
the glomerulus & into the Bowman’s capsule
- Results in a fluid called glomerular filtrate
3
...
Descending Limb:
- Na⁺ and Cl⁻ enter by DIFFUSION
- Water leaves
- The volume of the filtrate is reduced; the concentration is greater
-

Freely permeable to water

2
...
Ascending Limb:
- Cl⁻ and Na⁺ is pumped out
- Causes an increase in NaCl concentration in the medulla tissue

-

Impermeable to water
Filtrate concentration is reduced
Tissue fluid of the medulla contains high levels of NaCl at the kidney’s
pelvis
- This affects the water movement out of the collecting duct
- Na⁺ concentration increases through the medulla

DISTAL CONVOLUTED TUBULE:
-

Permeable to water
- Depends on ADH levels

-

Na⁺ can be actively pumped out if needed
H₂O moves out
Reduces filtrate volume

THE COLLECTING DUCT:
-

The filtrate becomes highly concentrated
H₂O leaves along a concentration gradient
Concentrates urine
H₂O permeability is affected by ADH

7A: Mechanism of ADH Action Through The Blood:
1
...
cAMP starts a series of reactions that causes vesicles within tubule cell lining to
move to & fuse with cell membranes
3
...
Water moves through channels, out of tubules & into surrounding capillaries by
osmosis

7A: ADH Action: During A Water Shortage:
1
...
Osmoreceptors in the hypothalamus detects the change
3
...
The distal tube & collecting tube become more permeable to water
5
...
Blood plasma concentration returns to normal

7A: ADH Action: During Water Loading:
1
...

3
...

5
...


Blood plasma becomes less concentrated
Osmoreceptors in the hypothalamus detects the change
Posterior pituitary gland releases less ADH
The distal tube & collecting tube becomes less permeable to water
Less water is reabsorbed; urine is less concentration & has more volume
Blood plasma concentration returns to normal

7A: How Animals’ Body Temperature RISES:
-

Conduction from the surroundings
Convection from the surroundings
Radiation from the surrounding

7A: How Animals’ Body Temperature LOWERS:
-

Water evaporation
Conduction to surroundings
Convection to surroundings
Radiation to surroundings

7A: Cooling Mechanisms:
VASODILATION OF BLOOD VESSELS:
1
...
More blood flows into capillaries & dilates them
3
...
The temperature gradient between the body’s surface and the environment
becomes GREATER
- Cooling via conduction and radiation INCREASES
SWEATING:

1
...
The hair erector pili muscles in the skin relax
- The hairs lie flat
2
...
Sphincter muscles around arterioles leading to superficial capillaries are
stimulated to contract
2
...
Less blood flows close to the body’s surface
4
...
Sweat glands secrete less sweat
- This reduces the amount of heat lost through evaporation
ERECTION OF HAIRS:
1
...
This creates an insulating layer by trapping air between the hairs
- This stops the heat from escaping
SHIVERING:
-

Is a reflex action
These effector muscles contract at a rapid & regular manner
Shivering generates sufficient heat to warm the blood & raise the body’s core
temperature

TOPIC 8:
8A: How A Response Is Generated By Effectors:
1
...
Impulses are sent along the sensory neurone; to the CNS; along the relay
neurone & along the motor neurone
3
...
The Na⁺/K⁺ pump creates concentration gradients across the membrane
2
...
The electrical gradient pulls K⁺ back into the cell
4
...
Voltage-dependent Na⁺ channels open
- Na⁺ flows into the axon- depolarising the membrane
2
...
Voltage dependent K⁺ channels open
- K⁺ leaves the axon- repolarising the membrane
4
...
The membrane is hyperpolarised
6
...
Action potential arrives & depolarises the presynaptic membrane
2
...
Causes synaptic vesicles to move to presynaptic membrane
4
...
The molecules diffuse across the gap & attached to specific protein receptor sites
on Na⁺ channels of the postsynaptic membrane
- Causes Na⁺ channels to open
- Na⁺ flows into nerve fibres
- Causes a change in potential difference across the
membrane & an EPSP is set up
THE MOVEMENT OF NEGATIVE IONS INWARDS RESULTS IN AN IPSP BEING SET UP
6
...
Action potential arrives & depolarises the presynaptic membrane
2
...

4
...

6
...

8
...
Increases the AMOUNT of neurotransmitter synthesised
2
...
Increases the EFFECT of the normal neurotransmitter
4
...
Prevents the REUPTAKE into the presynaptic knob
DECREASING THE RESPONSE:
1
...
Causes the neurotransmitters to LEAK from the vesicles and be DESTROYED by
enzymes
3
...
BLOCKS the receptors and prevents neurotransmitter BINDING

8A: How Sensory Receptors Work:
DEPENDENT ON MAINTAINING A NEGATIVE CHARGE OF THE CELL INTERIOR
- MAINTAINED BY Na⁺
1
...
- The smaller the stimulus, the smaller the generator potential
- The larger the stimulus, the larger the generator potential
3
...
Na⁺ moves into the rod cells through Na⁺ channels
- Na⁺/K⁺ pump moves them out again
2
...
The Na⁺ pump works at the same rate (pumping Na⁺ out of the rod cell)
- Interior becomes more negative than usual
- This hyperpolarisation is the generator potential of the rod cell
4
...
If it’s large enough to reach the threshold, or if several rods are stimulated at the
same time, the neurotransmitter substances are released into the synapse with
the bipolar cell
6
...
All sensory neurones leave the eye at the same time to form the optic nerve
- Leads to the brain

- ONCE THE VISUAL PIGMENT IS BLEACHED, THE ROD CANNOT BE STIMULATED
AGAIN UNTIL THE RHODOPSIN IS RESYNTHESISED
- IT TAKES ENERGY TO CONVERT TRANS-RETINAL → CIS-RETINAL WHICH THEN
JOINS TO OPSIN & FORMS RHODOPSIN

8A: Habituation:
THE DIMINISHING OF AN INNATE RESPONSE TO FREQUENT STIMULATION OF
STIMULI
1
...
Less neurotransmitter is released
3
...
A stimulus is received by a sensory receptor
2
...
It synapses with a relay neurone
- Then it synapses with a motor neurone within the grey matter
4
...
The motor end plate in the muscle transfers the stimulus to the muscle which
contracts
- This causes the body to move the body part away from danger

8B: Cranial Reflexes: AKA
...
Light falling on the sensory cells of the retina causes impulses to travel along
the neurones in the optic nerve to the brain
- The brighter the light, the larger the frequency of action potentials
2
...
The impulse travels along 2 neurones to further control centres

4
...
The impulses stimulates the effectors
6
...
Auxins affect the ability of plant cell walls to stretch
- Eg
...
IAA binds to the specific receptor sites on cell surface membranes
- This causes the active pumping of H+ into cell wall spaces
3
...
Allows microfibrils to slide past each other easily
- The walls can then stay very elastic & flexible
5
...
Cells eventually mature & the IAA is destroyed by enzymes
- The pH of cell walls rise
- Enzymes are inhibited
7
...
The seed absorbs water & swells
- Embryo is then activated
2
...
Gibberellin stimulates the aleurone layer to produce amylase

-

Diffuses into the endosperm & breaks the food stores down to provide the
embryo with the materials it needs for respiration & growth

4
...
Pr:
2
...
When Pr is converted to Pfr in the presence of light, it moves into the nucleus
through the pores in the nuclear membrane
2
...
PIF3 is a transcription factor
4
...
PIF3 activates gene transcription & mRNA formation if bound to Pfr
- It can then control different aspects of growth & developments in plants

8C: Producing Recombinant DNA:
1
...
ISOLATE THE REQUIRED GENE FROM THE PLASMID DNA OF THE BACTERIA:

-

Cut the plasmid with the same restriction endonucleases

3
...
USE THE VECTOR TO INTRODUCE THE GENE INTO THE HOST CELL:
- Use the host bacterial cell that the plasmid DNA was removed from
- The modified bacteria will now produce a different protein
- The new gene is expressed & causes protein synthesis

8C: Making An Artificial Copy of A Desired Gene:
1
...
It reverses the transcription process to produce complementary DNA (cDNA)
- It can act as an artificial gene

8C: Identifying Transferred Organisms: Replica Plating:
1
...
The master plate is inverted and pressed on a sterile velvet surface
- Leaves an imprint of colonies
- The master plate is saved for future uses if necessary
3
...
The replica plate is compared to the master plate
- The genetically modified colonies are identified & further grown

8C: Harvesting Human Insulin from GM Bacteria:

1
...
Cut out the insulin gene using restriction endonucleases
3
...
Join the plasmid & gene with DNA ligase to produce recombinant DNA
5
...
It’s continuously stirred by a tank bioreactor
7
...
Plasmid is extracted from the bacterial cell
2
...
The plant is infected with the modified bacteria & part of the plasmid (with the
engineered gene) becomes a part of the plants’ chromosomes
FOR EXAMPLE:
-

A
...
Introduce a copy of genes that code for a desired protein into genetic material of
an egg of a different animal species
2
...
The fertilised egg is placed inside a surrogate female, is born & grows to
maturity
4
...
mRNA samples are collected from known DNA samples

2
...
Each sample is given a fluorescent label
4
...
The microarray is scanned to measure the fluorescent light produced by the
different spots
- If both samples express a gene equally, a yellow light is shown
- If the experimental sample is expressed more than the control, a red light is
shown
- If the experimental sample is express more than the control, a green light is
shown



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