Lesson 3.3.4.1.2

3.3.4.1.2 Haemoglobin and oxygen transport Quiz: AQA Biology, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.3.4.1.2, Haemoglobin and oxygen transport: 20 multiple choice questions for the AQA Biology (7402), Unit 3: Organisms exchange substances with their environment, written with Revision Ninja.

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The 20 questions

  1. What is the quaternary structure of haemoglobin?

    • Four polypeptide chains, each with a haem group that binds one oxygen molecule.
    • A single polypeptide chain folded into a globular shape with no prosthetic group.
    • A long, unbranched chain of amino acids with a glycosidic bond at each binding site.
    • Two polypeptide chains joined by disulfide bridges, with a haem group on each chain.

  2. What is the Bohr effect?

    • An increase in carbon dioxide concentration reduces the affinity of haemoglobin for oxygen, shifting the dissociation curve right.
    • A rise in the pH of the blood causes haemoglobin to lose its quaternary structure and stop binding oxygen.
    • A fall in temperature causes haemoglobin to release all its oxygen immediately into the blood plasma.
    • An increase in carbon dioxide concentration increases the affinity of haemoglobin for oxygen, shifting the curve left.

  3. Why does the oxyhaemoglobin dissociation curve have a sigmoid shape?

    • The binding of the first oxygen changes the shape of haemoglobin, making the binding of further oxygen molecules easier.
    • Oxygen binds to each haem group independently with the same affinity, giving a straight line.
    • The binding of the first oxygen blocks further binding sites, so each following oxygen binds more slowly.
    • Haemoglobin contains a single binding site, so the curve rises in a straight line to full saturation.

  4. Which statement describes the loading of oxygen at the lungs?

    • Haemoglobin releases oxygen at the lungs because the carbon dioxide concentration is low there.
    • Haemoglobin is unaffected by oxygen partial pressure, so loading depends only on the heart rate.
    • Haemoglobin has a low affinity for oxygen, so it becomes unsaturated in the lungs.
    • Haemoglobin has a high affinity for oxygen, so it becomes almost fully saturated in the lungs.

  5. Which statement describes the unloading of oxygen in respiring muscle tissue?

    • Haemoglobin is destroyed by the muscle tissue, so the oxygen is released into the cytoplasm.
    • Carbon dioxide and a lower oxygen partial pressure cause haemoglobin to release oxygen to the tissue.
    • Haemoglobin releases oxygen only when the pH of the blood is above 8, which is rare in tissues.
    • Haemoglobin binds more oxygen because the carbon dioxide concentration in the muscle is high.

  6. Many animals have haemoglobins with different oxygen transport properties. Which adaptation does this reflect?

    • Animals in low-oxygen environments often have haemoglobins with a higher affinity for oxygen.
    • Animals in all environments have identical haemoglobin, so oxygen transport is the same for all.
    • Animals in low-oxygen environments always have haemoglobin with a lower affinity for oxygen.
    • Animals in low-oxygen environments have no haemoglobin, because it is produced only at high oxygen levels.

  7. A haemoglobin solution has a saturation of 60 percent at a partial pressure of oxygen of 4 kPa. What does this tell us about the solution?

    • At this partial pressure, 60 percent of the red blood cells have lost their haemoglobin entirely.
    • At this partial pressure, 60 percent of the haemoglobin binding sites carry oxygen.
    • At this partial pressure, 40 percent of the haemoglobin molecules have broken down into polypeptides.
    • At this partial pressure, 60 percent of the oxygen in the solution is dissolved in the plasma.

  8. Why is the Bohr effect important in an exercising muscle?

    • It increases the binding of oxygen to haemoglobin in the muscle, which blocks respiration.
    • It converts carbon dioxide into oxygen so that the muscle can respire aerobically.
    • It stops the release of oxygen to the muscle, so that the muscle conserves its energy supply.
    • It increases the release of oxygen to the muscle where carbon dioxide production is high.

  9. A researcher finds that the dissociation curve of an animal's haemoglobin lies to the left of human haemoglobin. What does this indicate?

    • The animal's haemoglobin has a lower affinity for oxygen at a given partial pressure.
    • The animal's haemoglobin cannot bind oxygen at any partial pressure in the environment.
    • The animal's haemoglobin is identical to human haemoglobin in every oxygen transport property.
    • The animal's haemoglobin has a higher affinity for oxygen at a given partial pressure.

  10. What is the role of red blood cells in oxygen transport?

    • They contain haemoglobin, which binds oxygen in the lungs and releases it in the tissues.
    • They contain xylem vessels, which carry oxygen from the lungs to the tissues by mass flow.
    • They contain phloem, which carries oxygen dissolved in sugar solutions to the heart.
    • They contain myoglobin, which binds oxygen in the plasma and carries it to the lungs.

  11. Which statement about the affinity of fetal haemoglobin for oxygen is consistent with its role?

    • Fetal haemoglobin has a higher affinity for oxygen, so oxygen can move from maternal blood to the fetus.
    • Fetal haemoglobin has a lower affinity for oxygen, so the fetus receives less oxygen from the mother.
    • Fetal haemoglobin is identical to adult haemoglobin, so it provides no advantage for oxygen transfer.
    • Fetal haemoglobin has no affinity for oxygen, so the fetus relies entirely on carbon dioxide transport.

  12. A student states that the oxygen dissociation curve shows haemoglobin binding oxygen at a constant rate. Which evaluation is correct?

    • The claim is partly correct, because binding is constant only in the presence of carbon dioxide.
    • The claim is correct, because haemoglobin binds oxygen at the same rate regardless of partial pressure.
    • The claim is wrong, because binding is cooperative, so the rate changes as more oxygen binds.
    • The claim is correct, because the sigmoid curve shows a constant gradient across the whole range.

  13. Which pigment is found in muscle tissue and has a higher affinity for oxygen than haemoglobin?

    • Myoglobin
    • Chlorophyll
    • Melanin
    • Carotene

  14. A person's blood has a low concentration of haemoglobin. What is the most likely effect on oxygen transport?

    • Less oxygen can be carried in the blood, so tissues may receive less oxygen for respiration.
    • Oxygen is carried entirely in the plasma, so haemoglobin concentration has no effect.
    • More oxygen is carried in the blood, because each haemoglobin molecule binds more oxygen.
    • The person's dissociation curve shifts to the right, so they absorb more oxygen at the lungs.

  15. Which of these is the correct sequence for the loading and unloading of oxygen by haemoglobin?

    • Loading and unloading both occur at the heart, which pumps oxygen to the lungs and tissues.
    • Loading at the tissues where oxygen partial pressure is low, then unloading at the lungs.
    • Loading and unloading both occur at the lungs, which controls the oxygen supply to all tissues.
    • Loading at the lungs where oxygen partial pressure is high, then unloading at tissues where it is low.

  16. A rise in temperature during exercise shifts the dissociation curve to the right. What is the effect on oxygen delivery?

    • Oxygen delivery is unchanged, because temperature has no effect on the affinity of haemoglobin.
    • Oxygen is released into the lungs, so the blood becomes depleted of oxygen before reaching the muscles.
    • Oxygen is released more readily to the working muscles, which helps to meet their demand.
    • Oxygen is bound more tightly to haemoglobin, so less oxygen is available to the muscles.

  17. In the lungs the oxygen partial pressure is high, and in a resting tissue it is lower. Which statement describes haemoglobin in the tissue?

    • It has a higher saturation in the tissue than in the lungs, so it stores oxygen in the tissue.
    • It releases oxygen in the lungs and binds oxygen in the tissue, which reverses the normal sequence.
    • It has a lower saturation in the tissue than in the lungs, so it releases oxygen to the tissue.
    • It has the same saturation at both sites, because oxygen partial pressure has no effect on binding.

  18. Which of these changes would shift the oxyhaemoglobin dissociation curve to the right?

    • A decrease in temperature of the blood at the tissue.
    • A rise in the pH of the blood as it passes through the lungs.
    • A decrease in carbon dioxide concentration in the blood.
    • An increase in carbon dioxide concentration in the blood.

  19. A student claims that haemoglobin is the best oxygen carrier for all animals. Evaluate this claim.

    • The claim is accurate, because haemoglobin is identical in every animal species that has been studied.
    • The claim is too strong, because animals have different haemoglobins adapted to their own environments.
    • The claim is accurate, because myoglobin carries less oxygen than haemoglobin in every animal tissue.
    • The claim is wrong, because haemoglobin carries no oxygen at all and only binds carbon dioxide.

  20. Why does myoglobin store oxygen in muscle more effectively than haemoglobin would?

    • It has a higher affinity for oxygen, so it binds oxygen even at the low partial pressures found in muscle.
    • It has a lower affinity than haemoglobin, so it releases oxygen more readily into the blood plasma.
    • It carries carbon dioxide away from the muscle, which frees its oxygen binding sites for storage.
    • It is found only in red blood cells, which store oxygen for the whole body at all times.

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