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A Level H2 Biology Human Physiology Quiz

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Questions

A-Level Biology H2 Quiz - Human Physiology

Name: __________________________
Class: __________________________
Date: __________________________
Score: _________ / 40

Duration: 45 minutes
Total Marks: 40
Instructions:

Answer all questions.
Write your answers in the spaces provided.
The number of marks is given in brackets [ ] at the end of each question or part question.
You may use a scientific calculator.

Section A: Multiple Choice & Short Structured Questions (Questions 1–5)

Answer all questions in this section.

1. Which of the following correctly describes the role of the sinoatrial node (SAN) in the cardiac cycle?
A. It delays the impulse to allow the ventricles to fill.
B. It initiates the wave of excitation that causes atrial contraction.
C. It conducts the impulse directly to the Purkinje fibres.
D. It prevents backflow of blood into the atria.
[1]

2. During strenuous exercise, the oxygen dissociation curve of haemoglobin shifts to the right. What is the primary physiological advantage of this shift?
A. Haemoglobin has a higher affinity for oxygen in the lungs.
B. Haemoglobin releases oxygen more readily to the respiring tissues.
C. Carbon dioxide is transported more efficiently as carbaminohaemoglobin.
D. The pH of the blood increases, enhancing enzyme activity.
[1]

3. Fig. 3.1 shows a nephron and its associated blood vessels.

Image pending generation for this question.

Fig. 3.1**

Which labelled part is primarily responsible for the reabsorption of glucose and amino acids via active transport?
A. Label A
B. Label B
C. Label C
D. Label D
[1]

4. Explain why the walls of the alveoli are only one cell thick.
[2]

5. State the function of the myelin sheath in a motor neurone and explain how it increases the speed of nerve impulse transmission.
[3]

Section B: Structured Questions (Questions 6–15)

Answer all questions in this section.

6. Fig. 6.1 shows the changes in pressure in the left atrium, left ventricle, and aorta during one cardiac cycle.

Image pending generation for this question.

Fig. 6.1**

(a) Identify the event occurring at point X, where the ventricular pressure exceeds the atrial pressure.
[1]

(b) Explain why the aortic pressure does not fall to zero during diastole.
[2]

(c) Calculate the heart rate in beats per minute if one complete cardiac cycle shown in Fig. 6.1 takes 0.8 seconds. Show your working.
[2]

Answer space

7. The formation of tissue fluid and its return to the circulatory system depends on hydrostatic and oncotic pressures.

(a) Define hydrostatic pressure in the context of capillary exchange.
[1]

(b) Explain how a decrease in plasma protein concentration (e.g., due to malnutrition) leads to oedema (accumulation of tissue fluid).
[3]

8. Fig. 8.1 shows the structure of a synapse.

Image pending generation for this question.

Fig. 8.1**

(a) Describe the sequence of events that leads to the release of acetylcholine into the synaptic cleft after an action potential arrives at the presynaptic knob.
[3]

(b) Acetylcholinesterase is an enzyme found in the synaptic cleft. Explain the importance of this enzyme in ensuring unidirectional transmission of impulses.
[2]

9. The kidney plays a vital role in homeostasis, particularly in osmoregulation.

(a) Describe the role of the loop of Henle in creating a hypertonic medulla.
[3]

(b) Antidiuretic hormone (ADH) regulates water reabsorption. Explain how ADH increases the permeability of the collecting duct to water.
[3]

10. Fig. 10.1 shows the changes in membrane potential of a neurone during an action potential.

Image pending generation for this question.

Fig. 10.1**

(a) Explain the mechanism responsible for the rapid rise in membrane potential from -70 mV to +40 mV.
[2]

(b) During the refractory period, the neurone cannot generate another action potential. Explain the physiological basis of the refractory period.
[2]

Section C: Data Response & Extended Structured Questions (Questions 11–20)

Answer all questions in this section.

11. Fig. 11.1 shows the effect of different concentrations of carbon dioxide on the rate of photosynthesis in C3 and C4 plants at two different temperatures.

Image pending generation for this question.

Fig. 11.1**

(a) With reference to Fig. 11.1, compare the efficiency of C3 and C4 plants at high carbon dioxide concentrations.
[2]

(b) Explain why C4 plants are better adapted to hot and dry environments than C3 plants, referring to the enzyme RuBisCO.
[3]

12. The immune system responds to pathogens through specific and non-specific mechanisms.

(a) Distinguish between active immunity and passive immunity.
[2]

(b) Describe the role of helper T-cells in the activation of B-lymphocytes during a primary immune response.
[3]

13. Fig. 13.1 shows the structure of the human heart.

Image pending generation for this question.

Fig. 13.1**

(a) Explain why the wall of the left ventricle is thicker than the wall of the right ventricle.
[2]

(b) Describe the function of the atrioventricular (AV) valves during ventricular systole.
[2]

14. Homeostasis involves negative feedback mechanisms.

(a) Define homeostasis.
[1]

(b) Explain how the body regulates blood glucose concentration when it rises above normal levels after a meal. Include the roles of insulin and target cells.
[4]

15. Fig. 15.1 shows the results of an experiment investigating the effect of temperature on the rate of respiration in yeast.

(Imagine a bar chart showing rate of CO2 production at 10°C, 20°C, 30°C, 40°C, 50°C, and 60°C. Rate increases up to 40°C then drops sharply at 50°C and is zero at 60°C.)

Fig. 15.1

(a) Explain the increase in the rate of respiration between 10°C and 40°C.
[2]

(b) Explain why the rate of respiration decreases rapidly above 40°C.
[2]

16. The nervous system coordinates responses to stimuli.

(a) State the difference between a sensory neurone and a motor neurone in terms of the direction of impulse transmission.
[1]

(b) Explain the term saltatory conduction and state where it occurs.
[2]

17. Gas exchange in humans occurs in the alveoli.

(a) State two features of the alveolar surface that facilitate efficient gas exchange.
[2]

(b) Explain how the ventilation mechanism maintains a concentration gradient for oxygen between the alveoli and the blood.
[2]

18. Fig. 18.1 shows the structure of a chloroplast.

Image pending generation for this question.

Fig. 18.1**

(a) Identify the site of the light-independent reaction (Calvin cycle).
[1]

(b) Explain the role of ATP and reduced NADP produced in the light-dependent reaction in the light-independent reaction.
[2]

19. The excretory system removes metabolic waste.

(a) Explain why urea is produced in the liver.
[2]

(b) Describe the process of ultrafiltration in the glomerulus.
[3]

20. Muscle contraction involves the interaction of actin and myosin.

(a) Describe the role of calcium ions in initiating muscle contraction.
[3]

(b) Explain the role of ATP in the sliding filament mechanism.
[2]

End of Quiz

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Answers

A-Level Biology H2 Quiz - Human Physiology (Answer Key)

Total Marks: 40

Section A: Multiple Choice & Short Structured Questions

1. B
[1]
Reasoning: The SAN is the pacemaker; it initiates the wave of excitation causing atrial contraction. A is the AV node, C is the Purkinje fibres/Bundle of His, D is the valves.

2. B
[1]
Reasoning: A rightward shift (Bohr effect) indicates lower affinity, meaning haemoglobin unloads oxygen more readily to tissues with high CO2/low pH (active tissues).

3. B
[1]
Reasoning: Glucose and amino acids are reabsorbed in the Proximal Convoluted Tubule (PCT) via active transport/co-transport.

Short diffusion distance [1]
Allows for rapid diffusion of gases (O2 and CO2) between alveolar air and blood capillaries [1]
[2]

Function: Electrical insulation [1]
Explanation: Forces the action potential to "jump" from one Node of Ranvier to the next (saltatory conduction) [1], which increases the speed of transmission compared to continuous conduction [1].
[3]

Section B: Structured Questions

6.
(a) Closure of the atrioventricular (AV) valve / Start of ventricular systole [1]
(Note: Point X is where ventricular pressure rises above atrial pressure, closing the mitral/bicuspid valve.)

(b)

Elastic recoil of the aorta wall [1]
Maintains pressure on the blood during diastole, ensuring continuous flow to the body [1]
[2]

(c)

Calculation: $60 \text{ seconds} / 0.8 \text{ seconds per beat}$ [1]
Answer: $75 \text{ beats per minute}$ [1]
[2]

7.
(a) The pressure exerted by the blood fluid against the capillary wall [1]
[1]

(b)

Decrease in plasma proteins lowers the oncotic (water) potential of the blood [1]
Reduces the osmotic force drawing water back into the capillaries at the venule end [1]
Net filtration pressure remains positive/outward, causing fluid to accumulate in tissue spaces (oedema) [1]
[3]

8.
(a)

Depolarisation of the presynaptic membrane opens voltage-gated calcium channels [1]
Calcium ions diffuse into the presynaptic knob [1]
Vesicles containing acetylcholine fuse with the presynaptic membrane and release ACh into the cleft by exocytosis [1]
[3]

(b)

Acetylcholinesterase hydrolyses acetylcholine into choline and ethanoic acid [1]
This prevents continuous stimulation of the postsynaptic membrane, allowing the synapse to reset for the next impulse (ensuring discrete signals) [1]
[2]

9.
(a)

Active transport of ions (Na+ and Cl-) out of the ascending limb [1]
Ascending limb is impermeable to water, so water stays in the tubule [1]
This creates a low water potential (hypertonic) in the medulla tissue fluid [1]
[3]

(b)

ADH binds to receptors on the collecting duct cells [1]
This triggers the insertion of aquaporins (water-permeable channels) into the cell surface membrane [1]
Increasing permeability allows water to be reabsorbed by osmosis into the hypertonic medulla [1]
[3]

10.
(a)

Voltage-gated sodium channels open [1]
Sodium ions diffuse rapidly into the axon down their electrochemical gradient, causing depolarisation [1]
[2]

(b)

Sodium channels are inactivated/closed and potassium channels are open [1]
The membrane is hyperpolarised or repolarising, so the threshold potential cannot be reached immediately [1]
[2]

Section C: Data Response & Extended Structured Questions

11.
(a)

C4 plants have a higher rate of photosynthesis at high CO2 concentrations compared to C3 plants [1]
C4 plants do not saturate as quickly / have a higher maximum rate [1]
[2]

(b)

C4 plants concentrate CO2 in bundle sheath cells [1]
This reduces photorespiration because high CO2 outcompetes O2 for the active site of RuBisCO [1]
C3 plants suffer from photorespiration in hot/dry conditions when stomata close and O2 builds up [1]
[3]

12.
(a)

Active immunity: Body produces its own antibodies/memory cells (long-term) [1]
Passive immunity: Antibodies are acquired from another source (e.g., mother, injection) (short-term) [1]
[2]

(b)

Helper T-cells recognise antigens presented by antigen-presenting cells [1]
They release cytokines [1]
Cytokines stimulate B-cells to divide by mitosis and differentiate into plasma cells and memory cells [1]
[3]

13.
(a)

Left ventricle pumps blood to the whole body (systemic circulation) [1]
Requires higher pressure to overcome greater resistance/distance compared to the right ventricle (pulmonary circulation) [1]
[2]

(b)

Prevent backflow of blood into the atria [1]
High ventricular pressure forces the valves to close [1]
[2]

14.
(a) The maintenance of a constant internal environment despite changes in external conditions [1]
[1]

(b)

Beta cells in the Islets of Langerhans detect high blood glucose [1]
Secrete insulin into the blood [1]
Insulin binds to receptors on target cells (liver, muscle) [1]
Increases permeability to glucose (GLUT4 translocation) and activates enzymes for glycogenesis [1]
Blood glucose levels decrease to normal [1]
(Max 4 marks)
[4]

15.
(a)

Increased kinetic energy of enzyme and substrate molecules [1]
More frequent successful collisions forming enzyme-substrate complexes [1]
[2]

(b)

High temperature breaks hydrogen bonds maintaining the tertiary structure of enzymes [1]
Active site changes shape (denaturation), substrate can no longer bind [1]
[2]

16.
(a)

Sensory: Impulse travels from receptor to CNS [1]
Motor: Impulse travels from CNS to effector [1]
(Accept "towards" vs "away from" CNS)
[1] (Note: Question asks for difference, 1 mark for clear distinction)

(b)

Action potential jumps from Node of Ranvier to Node of Ranvier [1]
Occurs in myelinated neurones [1]
[2]

17.
(a) Any two from:

Large surface area [1]
Thin walls / one cell thick [1]
Good blood supply / ventilation maintains gradient [1]
[2]

(b)

Ventilation brings fresh air (high O2) into alveoli [1]
Blood flow removes oxygenated blood, maintaining low O2 in capillaries [1]
[2]

18.
(a) Stroma [1]
[1]

(b)

ATP provides energy for the reduction of GP to TP [1]
Reduced NADP provides hydrogen/electrons for the reduction of GP to TP [1]
[2]

19.
(a)

Excess amino acids cannot be stored [1]
Deamination removes the amino group, forming toxic ammonia, which is converted to less toxic urea [1]
[2]

(b)

High hydrostatic pressure in the glomerulus (due to wider afferent arteriole than efferent) [1]
Forces small molecules (water, glucose, urea, ions) out of the blood [1]
Through the basement membrane and podocytes into Bowman’s capsule [1]
[3]

20.
(a)

Action potential travels down T-tubules [1]
Stimulates sarcoplasmic reticulum to release calcium ions [1]
Calcium binds to troponin, moving tropomyosin away from myosin-binding sites on actin [1]
[3]

(b)

ATP binds to myosin head, causing it to detach from actin [1]
Hydrolysis of ATP provides energy to cock the myosin head for the next power stroke [1]
[2]