Practise 59 real questions on Transport in mammals from 2021 to 2026. See the answer and explanation as soon as you answer.
Transport in mammals is one of the 11 main topics in our A Level Biology (Cambridge (CAIE) 9700) question bank, and about 9% of its real questions come from it. Tayyari Karo has 59 real questions on this topic from 2021 to 2026, from Paper 1, Paper 2; 51 are multiple choice and marked instantly, and the rest are structured questions with a model answer. By difficulty: 35 medium, 23 hard, 1 easy.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
These are real past-paper questions. Think of your answer first, then open the explanation.
Which reactions would be affected by an inhibitor of carbonic anhydrase?
1 CO2 + haemoglobin ⇌ carbaminohaemoglobin
2 CO2 + H2O ⇌ H2CO3
3 H2CO3 ⇌ H+ + HCO3−
Answer: D. 2 and 3 only
Carbonic anhydrase catalyses reactions 2 and 3.
Which statement correctly compares blood plasma and tissue fluid in a healthy person?
Answer: A. Blood plasma contains more protein than tissue fluid.
Large plasma proteins mostly cannot cross capillary walls, so blood plasma contains more protein than tissue fluid.
Which statement is correct about how oxygen combines with haemoglobin?
Answer: B. One oxygen molecule can combine with each haem group of the haemoglobin molecule.
Haemoglobin has four haem groups, each of which can bind one oxygen molecule, giving cooperative (positive) binding as each oxygen binds.
Which reactions would be slowed down by an inhibitor of carbonic anhydrase? 1 CO2 + haemoglobin → carbaminohaemoglobin. 2 CO2 + H2O → H2CO3. 3 H2CO3 → H+ + HCO3-.
Answer: D. 2 and 3 only
Carbonic anhydrase specifically catalyses the reversible conversion of CO2 and H2O to carbonic acid (reaction 2), whose subsequent dissociation into H+ and HCO3- (reaction 3) depends on carbonic acid being formed; reaction 1 (formation of carbaminohaemoglobin) does not involve carbonic anhydrase.
Which statements about the Bohr shift are correct?
1 The shift is accelerated by the action of carbonic anhydrase.
2 A decrease in blood pH will cause oxyhaemoglobin to dissociate.
3 A decrease in carbon dioxide concentration will cause more oxygen to bind to haemoglobin.
Answer: A. 1, 2 and 3
Carbonic anhydrase speeds up the conversion of CO2 to carbonic acid, generating H+ that lowers pH and shifts the oxygen dissociation curve, so all three statements correctly describe aspects of the Bohr shift: carbonic anhydrase accelerates it, lower pH causes oxyhaemoglobin to release oxygen, and lower CO2/higher pH favours oxygen binding.
A shortage of protein in the diet of children can lead to a disease (kwashiorkor) that causes excess tissue fluid to build up in the abdomen. What explains why a build-up of excess tissue fluid can occur in this disease?
Answer: B. A shortage of plasma proteins increases blood water potential; less tissue fluid returns to the blood.
Plasma proteins lower (make more negative) the water potential of blood, drawing tissue fluid back in at the venous end of capillaries by osmosis; a shortage of plasma proteins raises (makes less negative) blood water potential, so less tissue fluid returns to the blood, and it accumulates in the tissues.
| Session | Paper 1 | Paper 2 |
|---|---|---|
| May/June 2026 | 5 | 1 |
| May/June 2025 | 4 | 1 |
| October/November 2025 | 4 | 1 |
| May/June 2024 | 4 | 1 |
| October/November 2024 | 4 | 1 |
| May/June 2023 | 6 | 1 |
| October/November 2023 | 5 | – |
| May/June 2022 | 3 | – |
| October/November 2022 | 5 | 1 |
| May/June 2021 | 6 | – |
| October/November 2021 | 5 | 1 |
59 real A Level Biology (9700) questions on Transport in mammals from 2021 to 2026, from Paper 1, Paper 2. Each one shows the year, session and paper it came from.
Yes. Every question shows the correct answer and a short explanation the moment you answer.
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