TOPIC 6 EXAM QUESTIONS

Question 1

Exercise causes an increase in heart rate.
Describe the role of receptors and of the nervous system in this process.

Answer 1

1. Chemoreceptors detect rise in CO2 / H+ / acidity / carbonic acid / fall
   in pH
   OR
   Baro / pressure receptors detect rise in blood pressure;
2. Send impulses to cardiac centre / medulla;
3. More impulses to SAN;
4. By sympathetic (nervous system for chemoreceptors / CO2)
   OR
   By parasympathetic (nervous system for baro / pressure
   receptors / blood pressure);

Question 2

When the heart beats, both ventricles contract at the same time.
Explain how this is coordinated in the heart after initiation of the heartbeat
by the SAN.

Answer 2

1. Electrical activity only through Bundle of His / AVN;
2. Wave of electrical activity passes over / through both ventricles at the
   same time;

Question 3

The fovea of the eye of an eagle has a high density of cones. An eagle
focuses the image of its prey onto the fovea.
Explain how the fovea enables an eagle to see its prey in detail.

Answer 3

1. High (visual) acuity;
2. (Each) cone is connected to a single neurone;
   Accept no retinal convergence.
   Accept ‘bipolar/nerve cell’ for neurone.
3. (Cones send) separate (sets of) impulses to brain;

Question 4

The retina of an owl has a high density of rod cells.
Explain how this enables an owl to hunt its prey at night.
Do not refer to rhodopsin in your answer.

Answer 4

1. High (visual) sensitivity;
   Accept retinal convergence.
2. Several rods connected to a single neurone;
   Accept ‘bipolar/nerve cell’ for neurone
   Accept 2, ‘many’ or
3. Enough (neuro)transmitter to reach/overcome threshold
   OR
   Spatial summation to reach/overcome threshold; more for ‘several’

Question 5

Explain how applying pressure to the Pacinian corpuscle produces the
changes in membrane potential

Answer 5

1. (Pressure causes) membrane / lamellae to become deformed /
   stretched;
2. Sodium ion channels in membrane open and sodium ions move
   in;
3. Greater pressure more channels open / sodium ions enter.

Question 6

Explain how the resting potential of –70 mV is maintained in the sensory
neurone when no pressure is applied.

Answer 6

1. Membrane more permeable to potassium ions and less permeable to
   sodium ions;
2. Sodium ions actively transported / pumped out and potassium
   ions in.

Question 7

Multiple sclerosis is a disease in which parts of the myelin sheaths
surrounding neurones are destroyed. Explain how this results in slower
responses to stimuli.

Answer 7

1. Less / no saltatory conduction / action potential / impulse
   unable to ‘jump’ from node to node;
2. More depolarisation over length / area of membranes.

Question 8

topics to use in nerve essay

Answer 8

Enzymes
3.2.1.2 Structure of prokaryotic cells and of viruses
3.2.3 Transport across cell membranes
3.2.4 Cell recognition and the immune system
3.3.4.1 Mass transport in animals
3.4.2 DNA and protein synthesis
3.5.1 Photosynthesis
3.5.2 Respiration
3.6.1.1 Survival and response
3.6.1.2 Receptors
3.6.1.3 Control of heart rate
3.6.2.1 Nerve impulses
3.6.2.2 Synaptic transmission
3.6.3 Skeletal muscles
3.6.4.1 Principles of homeostasis

Question 9

Suggest two advantages of simple reflexes.

Answer 9

1. Rapid;
2. Protect against damage to body tissues;
3. Do not have to be learnt;
4. Help escape from predators;
5. Enable homeostatic control.

Question 10

Explain how a resting potential is maintained across the axon membrane in
a neurone

Answer 10

1. Higher concentration of potassium ions inside and higher
   concentration of sodium ions outside (the neurone)
   OR
   potassium ions diffuse out
   OR
   sodium ions diffuse in;
   Accept ‘more’ for ‘higher concentration’.
   Accept ‘sodium ions can’t diffuse in (due to
   alternative explanation).
2. (Membrane) more permeable to potassium ions (leaving
   than sodium ions entering)
   OR
   (Membrane) less permeable to sodium ions (entering
   than potassium ions leaving);
   Accept for ‘less permeable to sodium ions’ is
   ‘impermeable to sodium ions’ or ‘sodium
   gates/channels are closed’ (alternative
   explanation).
3. Sodium ions (actively) transported out and potassium ions in;

Question 11

Explain why the speed of transmission of impulses is faster along a
myelinated axon than along a non-myelinated axon.

Answer 11

1. Myelination provides (electrical) insulation;
   Reject thermal insulation.

Accept description of (electrical) insulation.
2. (In myelinated) saltatory (conduction)

OR

(In myelinated) depolarisation at nodes (of Ranvier);#

3. In non-myelinated depolarisation occurs along whole/length (of axon);
   Accept action potentials for depolarisation.

Question 12

A scientist investigated the effect of inhibitors on neurones. She added a
respiratory inhibitor to a neurone. The resting potential of the neurone
changed from –70 mV to 0 mV.

Answer 12

1. No/less ATP produced;
2. No/less active transport
   OR
   Sodium/potassium pump inhibited;
   Accept Na+ not/fewer moved out and K+ not/fewer
   moved in.
3. Electrochemical gradient not maintained
   OR
   (Facilitated) diffusion of ions causes change to 0 mV
   OR
   (Results in) same concentration of (sodium and
   potassium) ions (either side of membrane)
   OR
   No net movement of (sodium and potassium) ions;

Question 13

Describe the sequence of events involved in transmission across a cholinergic
synapse.
Do not include details on the breakdown of acetylcholine in your answer.

Answer 13

1. Depolarisation of presynaptic membrane;
   Accept action potential for depolarisation.
2. Calcium channels open and calcium ions enter (synaptic knob);

Accept Ca2+.

3. (Calcium ions cause) synaptic vesicles move to/fuse with
   presynaptic membrane and release
   acetylcholine/neurotransmitter;

Accept abbreviations for acetylcholine as term is in
the question.

4. Acetylcholine/neurotransmitter diffuses across (synaptic cleft);
   Accept abbreviations for acetylcholine as term is in
   the question.
5. (Acetylcholine attaches) to receptors on the postsynaptic membrane;
6. Sodium ions enter (postsynaptic neurone) leading to depolarisation;
   Accept Na+.
   Accept ‘action potential’ or ‘generator potential’ for
   depolarisation.

Question 14

Dopamine is a neurotransmitter released in some synapses in the brain.
The transmission of dopamine is similar to that of acetylcholine.
Dopamine stimulates the production of nerve impulses in postsynaptic
neurones.
Describe how.

Answer 14

1. (Dopamine) diffuses across (synapse);
2. Attaches to receptors on postsynaptic membrane;
   Ignore name/nature of receptor e.g. cholinergic
3. Stimulates entry of sodium ions and depolarisation/action potential;
   Accept Na+ for sodium ions
   Accept generator potential for action potential

Question 15

Dopamine has a role in numerous processes in the brain including pain
relief. The release of dopamine can be stimulated by chemicals called
endorphins produced in the brain. Endorphins attach to opioid receptors on
presynaptic neurones that release dopamine.
Morphine is a drug that has a similar structure to endorphins and can
provide pain relief.

Answer 15

1. Morphine attaches to opioid receptors;
   Reject reference to active site
2. (More) dopamine released (to provide pain relief);
   Reject receptors release dopamine

Question 16

GABA is a neurotransmitter released in some inhibitory synapses in the
brain. GABA causes negatively charged chloride ions to enter postsynaptic
neurones.
Explain how this inhibits postsynaptic neurones.

Answer 16

1. (Inside of postsynaptic) neurone becomes more
   negative/hyperpolarisation/inhibitory postsynaptic potential;
   Ignore K+
   Accept -75mV or any value below this as equivalent
   to more negative
   Accept ‘decrease in charge’
2. More sodium ions required (to reach threshold)
   OR
   Not enough sodium ions enter (to reach threshold);
   Accept Na+ for sodium ions
3. For depolarisation/action potential;
   Context must covey idea that depolarisation / action
   potential is less likely

Question 17

Use your knowledge of how myosin and actin interact to suggest how the
myosin molecule moves the mitochondrion towards the presynaptic
membrane.

Answer 17

1. Myosin head attaches to actin and bends / performs
   powerstroke;
2. (This) pulls mitochondria past / along the actin;
3. Other / next myosin head attaches to actin (and bends /
   performs powerstroke);

Question 18

) This movement of mitochondria happens when nerve impulses arrive at the
synapse.
Suggest and explain one advantage of the movement of mitochondria
towards the presynaptic membrane when nerve impulses arrive at the
synapse.

Answer 18

1. (Mitochondria) supply (additional) ATP / energy;
2. To move vesicles / for active transport of ions / for myosin to
   move past actin
   OR
   Re-synthesis / reabsorption of neurotransmitter / named
   neurotransmitter;

Question 19

Explain how a decrease in the concentration of calcium ions within muscle
tissues could cause a decrease in the force of muscle contraction.

Answer 19

1. (Less/No) tropomyosin moved from binding site
   OR
   Shape of tropomyosin not changed so binding site not
   exposed/available;
   Ignore troponin.
   Reject active site only once.
2. (Fewer/No) actinomyosin bridges formed;
   Accept actin and myosin do not bind.
   Reject active site only once.
3. Myosin head does not move
   OR
   Myosin does not pull actin (filaments)
   OR
   (Less/No) ATP (hydrol)ase (activation);
   Reject ATP synthase.

Question 20

In muscles, pyruvate is converted to lactate during prolonged exercise.
Explain why converting pyruvate to lactate allows the continued production
of ATP by anaerobic respiration.

Answer 20

1. Regenerates/produces NAD
   OR
   oxidises reduced NAD;
   Reject NADP and any reference to FAD.
   Accept descriptions of oxidation e.g. loss of hydrogen.
2. (So) glycolysis continues;

Question 21

The image shows glycogen granules present in skeletal muscle.
Explain their role in skeletal muscle.

Answer 21

1. As a store of glucose
   Ignore provide energy
   OR
   To be hydrolysed to glucose;
2. For respiration / to provide ATP;

Question 22

During vigorous exercise, the pH of skeletal muscle tissue falls. This fall in
pH leads to a reduction in the ability of calcium ions to stimulate muscle
contraction.
Suggest how.

Answer 22

1. Low pH changes shape of calcium ion receptors
   Do not accept tropomyosin does not move
2. Fewer calcium ions bind to tropomyosin;
   Accept troponin
3. Fewer tropomyosin molecules move away;
4. Fewer binding sites on actin revealed;
5. Fewer cross-bridges can form

Question 23

Describe the roles of calcium ions and ATP in the contraction of a
myofibri

Answer 23

1. Calcium ions diffuse into myofibrils from (sarcoplasmic) reticulum;
2. (Calcium ions) cause movement of tropomyosin (on actin);
3. (This movement causes) exposure of the binding sites on the
   actin;
4. Myosin heads attach to binding sites on actin;
5. Hydrolysis of ATP (on myosin heads) causes myosin heads to
   bend;
6. (Bending) pulling actin molecules;
7. Attachment of a new ATP molecule to each myosin head
   causes myosin heads to detach (from actin sites).

Question 24

ATP is an energy source used in many cell processes. Give two ways in
which ATP is a suitable energy source for cells to use.

Answer 24

1. Releases relatively small amount of energy / little energy lost as
   heat;
   Key concept is that little danger of thermal death of
   cells
2. Releases energy instantaneously;
   Key concept is that energy is readily available
3. Phosphorylates other compounds, making them more reactive;
4. Can be rapidly re-synthesised;
5. Is not lost from / does not leave cells.

Question 25

What is the role of ATP in myofibril contraction?

Answer 25

1. (Reaction with ATP) breaks/allows binding of myosin to actin/
   actinomyosin bridge;
2. Provides energy to move myosin head;

Question 26

Neonatal diabetes is a disease that affects newly born children. The
disease is caused by a change in the amino acid sequence of insulin.
This change prevents insulin binding to its receptor. Explain why this
change prevents insulin binding to its receptor.

Answer 26

1. Changes tertiary structure;
   Reject change in tertiary structure of receptor.
2. No longer complementary (to receptor);
   Reject ‘active site’ or reference to enzyme or
   substrate.

Question 27

Using your knowledge of the kidney, explain why glucose is found in the
urine of a person with untreated diabetes

Answer 27

1. High concentration of glucose in blood/filtrate;
   Accept tubule for filtrate.
2. Not all the glucose is (re)absorbed at the proximal convoluted tubule;
   Reject no glucose is (re)absorbed.
3. Carrier/co-transport proteins are working at maximum rate
   OR
   Carrier/co-transport proteins/ are saturated;

Question 28

Describe the role of glucagon in gluconeogenesis.

Answer 28

1. (Attaches to receptors on target cells and) activates/stimulates
   enzymes;
   Reject ‘produces enzymes’.
2. Glycerol/amino acids/fatty acids into glucose;

Question 29

Explain how increasing a cell’s sensitivity to insulin will lower the blood
glucose concentration.

Answer 29

1. (More) insulin binds to receptors;
2. (Stimulates) uptake of glucose by channel/transport proteins
   OR
   Activates enzymes which convert glucose to glycogen;

Question 30

Explain how inhibiting adenylate cyclase may help to lower the blood
glucose concentration.

Answer 30

1. Less/no ATP is converted to cyclic AMP/cAMP;
2. Less/no kinase is activated;
3. Less/no glycogen is converted to glucose
   OR
   Less/no glycogenolysis;

Question 31

Each year, a few people with type I diabetes are given a pancreas
transplant. Pancreas transplants are not used to treat people with type II
diabetes.
Give two reasons why pancreas transplants are not used for the treatment
of type II diabetes.

Answer 31

1. (Usually)Type II produce insulin;
2. Cells / receptors less sensitive / responsive (to insulin)
   OR
   Faulty (insulin) receptors;
3. (Treated / controlled by) diet / exercise;

Question 32

Give two ways in which people with type 1 diabetes control their blood
glucose concentration.

Answer 32

1. Treat with insulin (injection/infusion);
2. (Control) diet/control sugar intake;

Question 33

Alport syndrome (AS) is an inherited disorder that affects kidney glomeruli of
both men and women. Affected individuals have proteinuria (high quantities of
protein in their urine).
(a) Suggest how AS could cause proteinuria

Answer 33

1. Affects/damages basement membrane
   OR
   More protein channels/carriers in basement membrane;
2. Proteins can pass into the (glomerular) filtrate/tubule;

Question 34

Describe how ultrafiltration occurs in a glomerulus.

Answer 34

1. High blood/hydrostatic pressure;
   Ignore references to afferent and efferent arterioles
   Ignore ‘increasing/higher blood pressure’ as does not
   necessarily mean high
2. Two named small substances pass out eg water, glucose,
   ions, urea;
   Accept correct named ions
   Accept mineral ions/minerals
   Accept amino acids/small proteins
   Ignore references to molecules not filtered
3. (Through small) gaps/pores/fenestrations in (capillary)
   endothelium;
   Accept epithelium for endothelium
4. (And) through (capillary) basement membrane;

Question 35

Give the location of osmoreceptors in the body of a mammal.

Answer 35

Hypothalamus.

Question 36

When a person is dehydrated, the cell volume of an osmoreceptor
decreases.
Explain why

Answer 36

1. Water potential of blood will decrease;
2. Water moves from osmoreceptor into blood by osmosis

Question 37

Stimulation of osmoreceptors can lead to secretion of the hormone ADH.
Describe and explain how the secretion of ADH affects urine produced by
the kidneys.

Answer 37

1. Permeability of membrane / cells (to water) is increased;
2. More water absorbed from / leaves distal tubule / collecting duct;
3. Smaller volume of urine;
4. Urine becomes more concentrated.

Question 38

) Creatinine is a breakdown product of creatine found in muscle tissues.
Apart from age and gender, give two factors that could affect the
concentration of creatinine in the blood.

Answer 38

Muscle / body mass
Ethnicity
Exercise
Kidney disease –

Question 39

The acidic pH conditions created by osteoclasts cause the inactive form of
the protein osteocalcin to change into the active form of osteocalcin.
Suggest how.

Answer 39

1. (Change in pH) changes / breaks ionic / hydrogen bonds;
   Ignore ref. to peptide or sulfur-sulfur bonds
   Accept polar bonds
2. Changes tertiary structure;

Question 40

Binding of insulin leads to an increase in the rate of respiration in cells such
as osteoblasts.

Answer 40

1. (Insulin) leads to more transport proteins / channel (proteins) / carrier
   (proteins) for glucose;
   Ignore references to opening channels
   Accept co-transport / GLUT 1 or 4 protein
2. More glucose (for respiration / glycolysis) enters cell;

Question 41

Give two reasons why transmission across a cholinergic synapse is unidirectional.

Answer 41

1. (Only) the presynaptic
   neurone/knob/membrane releases/has
   neurotransmitter/acetylcholine;
   2.(Only) the postsynaptic
   neurone/membrane has receptors
   OR
   No receptors in the presynaptic
   neurone/membrane;

Question 42

Name the part of the body which releases antidiuretic hormone (ADH) into the blood

Answer 42

Posterior pituitary;

Question 43

Alcohol decreases the release of ADH into the blood.
Suggest two signs or symptoms which may result from a decrease in ADH.

Answer 43

1. Dehydration/thirst;
2. Frequent urination
   OR
   Increase in volume of urine;
   3.Less concentrated urine
   OR
   Dilute urine
   OR
   Urine paler/lighter in colour;

Question 44

Describe the effect of ADH on the collecting ducts in kidneys

Answer 44

1. (Stimulates) addition of channel proteins into
   membrane;
2. Increases permeability to water
   OR
   (More) water (re)absorbed;
3. By osmosis