plumiHaemoglobin and oxygen dissociation: OCR A‑Level Biology A questions
OCR A-Level Biology A past-paper questions on 3.1.2.5 Haemoglobin and oxygen dissociation, 2016–2025, with mark schemes and examiner’s reports where available.
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Q21(b)
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All 24 questions on Haemoglobin and oxygen dissociation, as a list
- June 2025, Paper 1, Q21(b) (4 marks): Explain how the structure of haemoglobin allows it to transport oxygen from the lungs to the tissues. [4]
- June 2025, AS Paper 1, Q11 (1 mark): Carbon dioxide is transported around the body either in the blood plasma or inside erythrocytes. Which statement is true about the transport of carbon dioxide?
- June 2025, AS Paper 1, Q12 (1 mark): The graph shows oxygen dissociation curves for adult haemoglobin, fetal haemoglobin and myoglobin. Myoglobin is a respiratory pigment found in muscle that acts
- June 2025, AS Paper 1, Q13 (1 mark): Which option describes the Bohr effect? A At the same partial pressure of oxygen, haemoglobin has a higher percentage saturation of oxygen. B Oxygen dissociates
- June 2024, AS Paper 1, Q24(a)(ii) (1 mark): Name the enzyme in an erythrocyte that allows haemoglobinic acid to be formed. [1]
- June 2023, Paper 1, Q16(c)(i) (1 mark): Sketch the oxygen dissociation curve for fetal haemoglobin. Answer on Fig. 16.3. [1]
- June 2023, Paper 1, Q16(c)(ii) (3 marks): Explain how the different affinities of maternal and fetal haemoglobin enable transfer of oxygen from the maternal circulation to the fetus. [3]
- June 2022, Paper 3, Q6(b) (3 marks): Haemoglobin plays a crucial role in transporting oxygen in animals. Several ions also have roles in oxygen transport. Three ions are listed in the table below.
- June 2022, AS Paper 2, Q4(d)(i) (2 marks): Explain how haemoglobin acts as a buffer. [2]
- June 2022, AS Paper 2, Q4(d)(ii) (2 marks): Fig. 4.2 shows the shape of oxygen dissociation curves for haemoglobin for a person at rest and during exercise. The changes to the dissociation curve at differ
- November 2021, AS Paper 1, Q15 (1 mark): Which of the options, A to D, best describes the chloride shift? A hydrogen carbonate ions and chloride ions moving into red blood cells B hydrogen carbonate io
- November 2020, Paper 3, Q6(a)(i) (2 marks): Outline why it is important that fetal haemoglobin has a higher oxygen affinity than adult haemoglobin. [2]
- November 2020, Paper 3, Q6(a)(ii) (2 marks): Myoglobin is a protein found in muscles. Oxygen binds to myoglobin. A student described the oxygen dissociation curve for myoglobin as follows: • When oxygen fi
- November 2020, Paper 3, Q6(b) (1 mark): Haemocyanin is an oxygen‑binding pigment that is found in many invertebrate animals, including lobsters. Fig. 6.2 shows the oxygen dissociation curves for haemo
- November 2020, AS Paper 1, Q17 (1 mark): The graph below shows the oxygen dissociation curve for adult human haemoglobin. 100 80 60 saturation of haemoglobin with oxygen (%) 40 20 0 0 20 40 60 80 100 p
- June 2019, Paper 1, Q2 (1 mark): Myoglobin is a protein found in muscle. Myoglobin has a very high affinity for oxygen at most partial pressures of oxygen. The figure below shows dissociation c
- June 2019, Paper 1, Q18(c) (2 marks): Squid blood contains a blue oxygen-carrying protein called haemocyanin. High partial pressures of carbon dioxide reduce the affinity for oxygen of haemocyanin.
- June 2019, AS Paper 1, Q10 (1 mark): Which of the following, A to D, shows the reaction catalysed by carbonic anhydrase? CO2 + H2O → H2CO3 A CO2 + Hb → HbCO2 B H+ + Hb → HHb C Hb + 4O2 → HbO8 D You
- June 2018, AS Paper 1, Q13 (1 mark): Carbon dioxide release during respiration can affect the % oxygen saturation of haemoglobin. The tertiary structure of haemoglobin is affected when carbon dioxi
- June 2016, AS Paper 1, Q24(a) (2 marks): Calculate the percentage increase in oxygen carried in fully saturated blood compared with oxygen carried in fully saturated plasma. Show your working. Answer =
- June 2016, AS Paper 1, Q24(b)(iii) (2 marks): Explain why erythrocytes do not make use of any of the oxygen that they are transporting. [2]
- June 2016, AS Paper 1, Q24(c)(i) (2 marks): • 100 cm3 of blood contains 20.1 cm3 of oxygen when fully saturated. • Calculate the volume (cm3) of oxygen being transported to the tissues per minute. Show yo
- June 2016, AS Paper 1, Q24(d)(i) (1 mark): What name is given to a change in the oxygen dissociation curve due to increasing carbon dioxide concentration? [1]
- June 2016, AS Paper 1, Q24(d)(ii) (2 marks): Letter T in Fig. 24 indicates the partial pressure of oxygen in actively respiring tissues. Explain why the blood off-loads more oxygen to actively respiring ti
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