8. Transport in mammals
A section of Biology, 9700
Listing 10 of 589 questions
Carbon dioxide is transported in the blood in various forms. Describe how carbon dioxide molecules reach red blood cells from respiring cells. shows part of a capillary network and some cells of the surrounding tissue. X Y venule end arteriole end State three ways in which the blood at Y differs from the blood at X other than in the concentration of carbon dioxide. 1. 2. 3. An enzyme in red blood cells catalyses the reaction between carbon dioxide and water as blood flows through respiring tissues. CO2 + H2O H2CO3 enzyme H+ + HCO3 – Name the enzyme that catalyses this reaction. Explain the significance of this reaction in the transport of carbon dioxide. shows the effect of increasing the carbon dioxide concentration on the oxygen haemoglobin dissociation curve. partial pressure of oxygen / kPa percentage saturation of haemoglobin with oxygen partial pressure CO2 1.0 kPa partial pressure CO2 1.5 kPa State the percentage saturation of haemoglobin with oxygen at a partial pressure of 5 kPa of oxygen when the partial pressure of carbon dioxide is: 1.0 kPa 1.5 kPa The percentage saturation of haemoglobin with oxygen decreases as the partial pressure of carbon dioxide increases. Explain how this happens. Name the effect of increasing carbon dioxide concentration on the oxygen dissociation curve. Explain the importance of the effect of carbon dioxide on haemoglobin as shown in .
9700_s11_qp_21
THEORY
2011
Paper 2, Variant 1
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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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