8.2. Transport of oxygen and carbon dioxide
A subsection of Biology, 9700, through 8. Transport in mammals
Listing 10 of 241 questions
Haemoglobin is a complex protein molecule made of four separate subunits, as shown in . P The shading represents the two different polypeptides that form a molecule of haemoglobin. State the names of the two different polypeptides. Identify the structure labelled P in . shows some of the levels of protein structure. State the level of protein structure that is not shown in . Haemoglobin is involved in the transport of carbon dioxide. Molecules of carbon dioxide enter red blood cells as the cells travel in capillaries through muscle tissue. Some of these molecules are converted to carbonic acid. Explain how haemoglobin is involved in the transport of carbon dioxide molecules that are not converted to carbonic acid. When haemoglobin associates with oxygen it forms oxyhaemoglobin. State the precise site in the mammalian body where haemoglobin molecules bind with oxygen. The compound 2,3‑diphosphoglycerate (2,3‑DPG) is produced in red blood cells. 2,3‑DPG binds to haemoglobin and stabilises it. shows oxygen dissociation curves when red blood cells have high and low concentrations of 2,3‑DPG. percentage saturation of haemoglobin with oxygen partial pressure of oxygen / kPa low concentration of 2,3-DPG high concentration of 2,3-DPG P50 is the partial pressure of oxygen when haemoglobin is 50% saturated. The P50 is used to compare the affinity of haemoglobin for oxygen under different conditions. Use the information in to describe the effect of an increase in the concentration of 2,3‑DPG on the oxygen dissociation curve. Blood is stored in blood banks for use in hospitals during operations. The concentration of 2,3‑DPG in red blood cells decreases when blood is stored in a blood bank. State and explain the effect that the use of blood taken from a blood bank has on the supply of oxygen to the tissues of a person during an operation.
9700_w23_qp_23
THEORY
2023
Paper 2, Variant 3
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The graph shows the effect of different partial pressures of carbon dioxide (CO2) on the oxygen dissociation curve for haemoglobin. partial pressure of oxygen / kPa percentage saturation of haemoglobin with oxygen partial pressure CO partial pressure CO2 1.0 1.0 kPa kPa partial pressure CO partial pressure CO2 1.5 1.5 kPa kPa partial pressure CO2 1.0 kPa partial pressure CO2 1.5 kPa What is the change in percentage oxygen saturation of haemoglobin at a partial pressure of oxygen of 6 kPa as the partial pressure of carbon dioxide changes from 1.0 kPa to 1.5 kPa?
9700_w24_qp_13
MCQ
2024
Paper 1, Variant 3
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Malaria is an infectious disease caused by the protoctist, Plasmodium. As part of its lifecycle, Plasmodium infects human red blood cells. Researchers can compare haemoglobin from the red blood cells of a healthy person with haemoglobin from a person with malaria. Throughout the world, most deaths from malaria are caused by P. vivax and P. falciparum. Name one other species of Plasmodium that causes malaria. Plasmodium In the laboratory, oxygen at different partial pressures can be bubbled through a solution of haemoglobin to determine the percentage saturation of haemoglobin at each partial pressure. A graph constructed from the results is known as an oxygen dissociation curve. is an oxygen dissociation curve for normal adult haemoglobin in humans. partial pressure of oxygen / kPa percentage saturation of haemoglobin with oxygen In the experiment used to obtain the results shown in , the temperature and pH were standardised. Explain what the researchers would consider when deciding which temperature and pH to use in the experiment. Using a different, more rapid technique, researchers compared the haemoglobin contained in red blood cells of a healthy person with the haemoglobin of a person with malaria who had been infected with P. vivax. By analysing the results, the researchers concluded that the oxygen dissociation curve of a person with malaria would be shifted to the right. With reference to , explain how a shift to the right of the oxygen dissociation curve would affect oxygen loading in the lungs, and unloading in respiring tissues, in a person with malaria. A red blood cell that is infected with Plasmodium cannot carry out its function as effectively as a normal red blood cell. Describe how the size and structure of a red blood cell is related to its function, other than the fact that it contains a very large number of haemoglobin molecules.
9700_w24_qp_22
THEORY
2024
Paper 2, Variant 2
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Questions Discovered
241