8.2. Transport of oxygen and carbon dioxide
A subsection of Biology, 9700, through 8. Transport in mammals
Listing 10 of 241 questions
Explain how the structure of red blood cells is suited to their function of transporting oxygen to body tissues. The circulating red blood cell is metabolically active but only lives for about 120 days. During this time, some important enzymes are gradually broken down and this may contribute to the death of the cell. Explain why the red blood cell is not able to replace important enzymes that have been broken down. Red blood cells are broken down by phagocytic cells in the liver and spleen. The haemoglobin is broken down into haem and globin before further processing. Some of the components of haemoglobin are re-used in the body. Name the mineral ion released from the breakdown of haem. State the products of globin hydrolysis. Haemoglobin plays an important role in carrying oxygen and carbon dioxide. summarises some of the events that occur as blood enters a capillary located in an area of actively respiring cells. CO2 CO2 Cl – Cl – HbCO2 H2CO3 H2O H2O red blood cell blood plasma capillary endothelium tissue fluid respiring tissue + X HbO8 Hb HCO3– HCO3– HHb H+ CO2 4O2 4O2 State the name of the enzyme that catalyses the reaction occurring at X. With reference to , describe and explain how carbon dioxide (CO2) and hydrogen ions (H+) play a role in the unloading of oxygen from haemoglobin.
9700_s11_qp_22
THEORY
2011
Paper 2, Variant 2
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In mammals, haemoglobin is used to transport oxygen and myoglobin is used to store oxygen in muscles. shows the oxygen dissociation curves for myoglobin, fetal haemoglobin and adult haemoglobin. percentage saturation with oxygen partial pressure of oxygen / kPa fetal haemoglobin adult haemoglobin myoglobin Name the cells in which haemoglobin is found. Use to determine the percentage saturation of myoglobin and adult haemoglobin when the partial pressure of oxygen is 3 kPa. myoglobin adult haemoglobin There is a large difference between the percentage saturation of myoglobin and that of adult haemoglobin at low partial pressures of oxygen. Suggest reasons for this. Fetal haemoglobin has a different oxygen binding affinity to that of adult haemoglobin, as shown in . Normally, after birth, the production of the fetal form stops and the adult form is produced. In a rare condition known as Hereditary Persistence of Fetal Haemoglobin (HPFH), fetal haemoglobin continues to be produced well into adulthood in addition to adult haemoglobin. This condition, however, usually lacks any symptoms. Explain, with reference to , the significance of the difference in oxygen binding affinity between fetal and adult haemoglobin. Suggest why HPFH usually lacks symptoms. Sketch on the dissociation curve you would expect for adult haemoglobin if the concentration of carbon dioxide is increased. percentage saturation of haemoglobin with oxygen partial pressure of oxygen / kPa adult haemoglobin
9700_s11_qp_23
THEORY
2011
Paper 2, Variant 3
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Haemoglobinopathies are inherited conditions linked to the structure and function of haemoglobin. Sickle cell anaemia is one of these conditions in which the transport and delivery of oxygen to tissues is less than normal. An investigation was carried out to discover the effect of sickle cell anaemia on the ability of blood to carry oxygen. Blood samples were taken from two people: • person L without sickle cell anaemia • person M with sickle cell anaemia. The percentage saturation of haemoglobin with oxygen was determined over a range of partial pressures of oxygen. shows oxygen haemoglobin dissociation curves for the two blood samples. partial pressure of oxygen / kPa percentage saturation of haemoglobin with oxygen M L P50 is the partial pressure of oxygen at which haemoglobin is 50% saturated with oxygen. It is taken as a measurement of the affinity of haemoglobin for oxygen. State the P50 for the two blood samples, L and M. L M With reference to , describe how the dissociation curve for person M differs from the dissociation curve for person L. Explain the advantage of the position of the dissociation curve for people with sickle cell anaemia. The partial pressure of oxygen in the lungs at sea level is about 13.5 kPa. At an altitude of 3000 metres the partial pressure of oxygen in the lungs is about 7.5 kPa. When people move from sea level to high altitude they become adapted to the low partial pressure of oxygen. Describe and explain how humans become adapted to the low partial pressure of oxygen at high altitude. Vaccination is used to control the spread of diseases, such as measles. Explain why vaccination cannot be used to prevent sickle cell anaemia.
9700_s12_qp_21
THEORY
2012
Paper 2, Variant 1
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Questions Discovered
241