A-Level Biology Topic 8: Transport in Mammals MCQs – 30 Practice Questions with Answers (Cambridge 9700)
Free practice for Cambridge A-Level Biology 9700 on transport in mammals, with every question followed by a short explanation to help you check your understanding.
The Circulatory System and Blood Vessels
Q1. What type of circulation do mammals have?
- (A) A closed double circulation
- (B) An open circulation, with blood bathing tissues directly
- (C) A single circulation through the heart once per circuit
- (D) No circulation, with diffusion alone supplying all cells
Show Answer
Answer: A – Mammals have a closed double circulation, with blood in vessels and two passes through the heart.
Q2. Which vessel carries deoxygenated blood from the heart to the lungs?
- (A) The aorta
- (B) The pulmonary vein, carrying blood to the heart
- (C) The pulmonary artery
- (D) The vena cava
Show Answer
Answer: C – The pulmonary artery carries deoxygenated blood from the heart to the lungs.
Q3. Which vessel carries oxygenated blood from the lungs to the heart?
- (A) The pulmonary artery
- (B) The aorta
- (C) The vena cava
- (D) The pulmonary vein
Show Answer
Answer: D – The pulmonary vein carries oxygenated blood from the lungs to the heart.
Q4. Which vessel carries oxygenated blood from the heart to the rest of the body?
- (A) The vena cava
- (B) The aorta
- (C) The pulmonary artery
- (D) The pulmonary vein
Show Answer
Answer: B – The aorta carries oxygenated blood from the heart to the body tissues.
Q5. How are arteries adapted to carry blood at high pressure?
- (A) Thick muscular and elastic walls
- (B) They have valves and very thin walls
- (C) They are one cell thick throughout
- (D) They have no walls at all
Show Answer
Answer: A – Thick muscular and elastic walls let arteries withstand and smooth out high pressure.
Q6. Why do veins have valves?
- (A) To speed blood up to arterial pressure
- (B) To carry oxygen to the lungs
- (C) To prevent backflow
- (D) To filter out red blood cells
Show Answer
Answer: C – Valves in veins prevent backflow when blood pressure is low.
Q7. Why are capillary walls only one cell thick?
- (A) To withstand the highest blood pressure
- (B) To allow rapid exchange
- (C) To store large volumes of blood
- (D) To prevent any substances leaving the blood
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Answer: B – A one-cell-thick wall gives a short diffusion distance for exchange.
Q8. What is the main component of blood and tissue fluid?
- (A) Protein only
- (B) Lipid only
- (C) Red blood cells only
- (D) Water
Show Answer
Answer: D – Water is the main component of blood and tissue fluid.
Q9. Which property of water helps it act as a transport medium in blood?
- (A) It cannot dissolve any solutes
- (B) It boils at body temperature
- (C) It is a good solvent
- (D) It is always solid in the body
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Answer: C – Water acts as a solvent, carrying dissolved substances around the body.
Q10. How is tissue fluid formed at the arteriole end of a capillary network?
- (A) Pressure forces fluid out
- (B) Red blood cells burst open
- (C) Valves pump fluid backwards
- (D) The capillary wall dissolves
Show Answer
Answer: A – High pressure at the arteriole end forces fluid out, while large plasma proteins remain inside.
Oxygen and Carbon Dioxide Transport
Q11. What is the role of haemoglobin in red blood cells?
- (A) It carries carbon dioxide only
- (B) It binds and carries oxygen
- (C) It produces antibodies
- (D) It clots the blood
Show Answer
Answer: B – Haemoglobin inside red blood cells binds and transports oxygen.
Q12. What happens to carbon dioxide when it enters a red blood cell?
- (A) It is stored unchanged in the cell forever
- (B) It is turned into oxygen
- (C) It leaves the cell at once
- (D) It forms hydrogencarbonate ions
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Answer: D – Carbonic anhydrase catalyses the conversion of carbon dioxide towards hydrogencarbonate ions.
Q13. What is haemoglobinic acid?
- (A) Haemoglobin combined with oxygen
- (B) An enzyme in plasma
- (C) Haemoglobin plus hydrogen ions
- (D) A type of white blood cell
Show Answer
Answer: C – Haemoglobinic acid forms when haemoglobin takes up hydrogen ions during carbon dioxide transport.
Q14. What is carbaminohaemoglobin?
- (A) Haemoglobin plus carbon dioxide
- (B) Haemoglobin combined with oxygen only
- (C) Haemoglobin broken down in the liver
- (D) Plasma carrying dissolved oxygen
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Answer: A – Carbaminohaemoglobin is haemoglobin with carbon dioxide bound directly to it.
Q15. What is the chloride shift?
- (A) Chloride ions moving out of red blood cells as oxygen binds
- (B) Chloride ions enter as hydrogencarbonate leaves
- (C) Chloride ions leaving the body in urine only
- (D) Chloride ions turning into oxygen
Show Answer
Answer: B – In the chloride shift, chloride ions enter red blood cells as hydrogencarbonate ions leave them.
Q16. Why is the chloride shift important?
- (A) It stops all carbon dioxide transport
- (B) It destroys red blood cells
- (C) It prevents oxygen binding
- (D) It maintains electrical neutrality
Show Answer
Answer: D – The shift balances charge, so hydrogencarbonate can keep leaving the cell and more carbon dioxide can be taken up.
Q17. How is most carbon dioxide carried in the blood?
- (A) Dissolved in plasma as a gas only
- (B) Bound to platelets only
- (C) As hydrogencarbonate ions in the plasma
- (D) As oxygen in red blood cells
Show Answer
Answer: C – Most carbon dioxide is carried as hydrogencarbonate ions in the plasma.
Q18. What shape is the oxygen dissociation curve for adult haemoglobin?
- (A) A straight line
- (B) An S-shaped, or sigmoid, curve
- (C) A circle
- (D) A flat horizontal line
Show Answer
Answer: B – The adult haemoglobin dissociation curve is S-shaped.
Q19. At the high partial pressure of oxygen in the lungs, what does haemoglobin do?
- (A) It loads with oxygen readily
- (B) It releases all its oxygen at once
- (C) It turns into carbon dioxide
- (D) It stops binding any gas
Show Answer
Answer: A – At high partial pressure in the lungs, haemoglobin loads with oxygen.
Q20. At the low partial pressure of oxygen in respiring tissues, what does haemoglobin do?
- (A) It binds oxygen more tightly
- (B) It produces new red blood cells
- (C) It turns into plasma
- (D) It releases oxygen for respiration
Show Answer
Answer: D – At low partial pressure in respiring tissues, haemoglobin unloads oxygen.
The Heart and the Cardiac Cycle
Q21. What is the Bohr shift?
- (A) A shift of the dissociation curve to the left in respiring tissues
- (B) A shift of blood from arteries to veins
- (C) The curve shifts right in respiring tissues
- (D) A change in heart rate only
Show Answer
Answer: C – High carbon dioxide in respiring tissues shifts the curve right, so haemoglobin releases more oxygen there.
Q22. Why is the wall of the left ventricle thicker than the wall of the right ventricle?
- (A) The left ventricle holds more valves
- (B) It pumps blood around the whole body
- (C) The left ventricle is larger in volume only
- (D) The right ventricle does not contract
Show Answer
Answer: B – The left ventricle needs a thicker wall to generate the higher pressure for the systemic circulation.
Q23. Why are ventricular walls thicker than atrial walls?
- (A) Ventricles pump at higher pressure
- (B) Atria never contract
- (C) Ventricles store blood for longer
- (D) Atria carry only deoxygenated blood
Show Answer
Answer: A – Ventricles pump blood out of the heart, while atria only push blood a short distance into the ventricles.
Q24. During ventricular systole, what happens to pressure and valves?
- (A) Pressure falls and all valves open
- (B) Pressure stays constant and no valves move at all
- (C) The heart stops beating
- (D) Pressure rises, atrioventricular valves close
Show Answer
Answer: D – Rising ventricular pressure closes the atrioventricular valves and then opens the semilunar valves.
Q25. What initiates each heartbeat?
- (A) The vena cava
- (B) The aorta
- (C) The sinoatrial node
- (D) The pulmonary vein
Show Answer
Answer: C – The sinoatrial node initiates the impulse that starts each cardiac cycle.
Q26. What is the role of the atrioventricular node in the cardiac cycle?
- (A) It stops the heartbeat completely
- (B) It delays the impulse briefly
- (C) It pumps blood directly to the lungs
- (D) It closes the semilunar valves
Show Answer
Answer: B – The atrioventricular node delays the impulse, allowing atrial contraction to complete first.
Q27. What is the role of Purkyne tissue in the cardiac cycle?
- (A) It spreads the impulse through ventricles
- (B) It carries blood to the heart muscle itself
- (C) It opens the atrioventricular valves
- (D) It produces red blood cells
Show Answer
Answer: A – Purkyne tissue spreads the impulse through the ventricles, coordinating their contraction.
Q28. During diastole, what happens in the heart?
- (A) The chambers contract at maximum pressure
- (B) The valves all stay closed permanently
- (C) Blood stops moving entirely
- (D) The chambers relax and fill with blood
Show Answer
Answer: D – During diastole the heart muscle relaxes and the chambers fill with blood.
Q29. Which sequence correctly orders the main stages of the cardiac cycle?
- (A) Ventricular systole, atrial systole, diastole
- (B) Diastole, ventricular systole, atrial systole
- (C) Atrial systole, ventricular systole, diastole
- (D) Ventricular systole, diastole, atrial systole
Show Answer
Answer: C – The cycle runs through atrial systole, then ventricular systole, then diastole.
Q30. A patient has a blocked pulmonary artery. Which journey is directly affected?
- (A) Blood from the lungs to the left atrium
- (B) Blood from the heart to the lungs
- (C) Blood from the body to the right atrium
- (D) Blood from the left ventricle to the body
Show Answer
Answer: B – The pulmonary artery carries blood from the heart to the lungs, so a blockage affects that journey.
Work through any questions you missed again, then revise those areas before moving on to the next topic.