AS Level Biology chapter 8: Transport in mammals MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
35 exam-style questions on Transport in mammals, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Transport of oxygen and carbon dioxide11 questions
The heart11 questions
Ten Transport in mammals questions with answers
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. What is the chloride shift?
A
movement of chloride ions from the plasma into the tissue fluid as CO2 enters the blood
B
movement of chloride ions out of red blood cells as oxygen enters
C
binding of chloride ions to haemoglobin so that it releases more oxygen
D
hydrogencarbonate ions move out of red cells as chloride ions move in
Show answer
Answer: D. HCO3− diffuses out of the red cell into the plasma, and Cl− moves in to maintain electrical neutrality.
2. How does a muscular artery differ from an elastic artery such as the aorta?
A
it has more smooth muscle, so it can constrict or dilate to control blood flow to an organ
B
it carries blood at a higher pressure than the aorta, because it is further from the heart
C
it has semilunar valves along its length to stop blood flowing backwards
D
it has a thicker layer of elastic fibres, so it stretches and recoils with every heartbeat
Show answer
Answer: A. Muscular arteries have a thick layer of smooth muscle to change their diameter; elastic arteries near the heart need more elastic tissue.
3. Why does tissue fluid contain very little protein compared with blood plasma?
A
plasma proteins are broken down by enzymes in the tissue fluid as soon as they leave
B
plasma proteins are too large to pass through the capillary wall
C
plasma proteins are taken up by red blood cells as blood passes through the capillary
D
plasma proteins are removed from the blood by the liver before it enters the capillaries
Show answer
Answer: B. Most plasma proteins are too large to leave, which is also why they lower the water potential of blood and help return water at the venous end.
4. How is carbaminohaemoglobin formed?
A
carbon monoxide binds to the iron in haem and stays there permanently
B
hydrogencarbonate ions bind to the amine groups of the haemoglobin polypeptides
C
carbon dioxide binds to the iron of the haem groups, in place of oxygen
D
carbon dioxide binds to amine groups of the haemoglobin polypeptides
Show answer
Answer: D. Some CO2 combines directly with amine groups on the globin chains, not with the iron, forming carbaminohaemoglobin.
5. A patient has a partly blocked coronary artery. What is the direct effect on the region of heart muscle that the artery supplies?
A
the blood in the ventricle cannot reach the aorta
B
the muscle cells receive too little oxygen to respire aerobically and release enough energy
C
the muscle cells receive too little blood from the vena cava to contract
D
the atrioventricular valve in that region can no longer close
Show answer
Answer: B. Coronary arteries branch from the aorta and supply the heart muscle itself with oxygen and glucose. A blockage starves that region of oxygen for aerobic respiration, so it may not contract properly. Blood in the heart chambers does not nourish the muscle.
6. When does the aortic semilunar valve open?
A
when pressure in the left ventricle exceeds pressure in the aorta
B
when pressure in the left atrium exceeds pressure in the left ventricle
C
when the ventricle relaxes
D
when pressure in the aorta exceeds pressure in the ventricle
Show answer
Answer: A. Valves open when the pressure behind them is greater than the pressure in front. When aortic pressure is higher, the valve closes.
7. What is the Bohr shift?
A
the fall in oxygen saturation of haemoglobin at high altitude, where the partial pressure is lower
B
a shift of the curve to the left at high CO2 concentration, so haemoglobin holds its oxygen more tightly
C
a shift of the curve to the right at high CO2 concentration, so haemoglobin releases oxygen more readily
D
the change that makes haemoglobin bind carbon dioxide instead of oxygen in respiring tissues
Show answer
Answer: C. More CO2 means more H⁺, which lowers haemoglobin's affinity for O2; the curve moves right and more oxygen is unloaded.
8. Fully saturated blood carries 20 cm3 oxygen per 100 cm3. Blood leaves the lungs 96% saturated and leaves a muscle 36% saturated. How much oxygen does 100 cm3 of blood release to the muscle?
A
7.2 cm3
B
19.2 cm3
C
12 cm3
D
60 cm3
Show answer
Answer: C. Saturation falls by 96 − 36 = 60%, and 60% of 20 cm3 = 12 cm3. 7.2 and 19.2 are the amounts still carried at 36% and 96%.
9. Why is there a short delay at the atrioventricular node (AVN)?
A
so the atria can empty completely before the ventricles begin to contract
B
so the wave of excitation can travel to the base of the ventricles first
C
so the SAN can recover before it fires again and starts the next beat
D
so the semilunar valves can close before the atrioventricular valves open
Show answer
Answer: A. The delay lets blood from the atria fill the ventricles completely before ventricular systole begins.
10. What is the main function of the elastic tissue in the wall of the aorta?
A
it stretches as the ventricle contracts and recoils afterwards, which smooths out the flow of blood
B
it closes to prevent backflow of blood into the ventricle during diastole
C
it contracts after each beat to push the blood on towards the arterioles
D
it lets oxygen and glucose diffuse quickly through the wall into the surrounding tissues
Show answer
Answer: A. Elastic fibres stretch at high pressure and recoil in diastole, keeping blood flowing and reducing pressure swings.
35, each with the answer and a short explanation, across 3 topics: The circulatory system, Transport of oxygen and carbon dioxide, The heart. Every chapter test draws ten of them, so you can take it many times.
Is the AS Level Biology chapter 8 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
