8.2. Transport of oxygen and carbon dioxide
A subsection of Biology, 9700, through 8. Transport in mammals
Listing 10 of 241 questions
Control of heartbeat is myogenic. This means the electrical activity controlling the rhythm of a regular heartbeat begins in the heart muscle itself. Atrial fibrillation (AF) is an abnormal heart rhythm that causes rapid and irregular contractions of the atria. Untreated cases of AF can lead to a stroke. A stroke is caused when a small blood clot, often forming in the left atrium, is carried by the blood to the brain where it blocks a small artery and leads to brain damage. List all of the structures through which a blood clot in the left atrium must travel to reach the blood vessels supplying the brain. The structures must be listed in the correct sequence. Explain why blocking a small artery in the brain leads to brain damage. A common cause of AF is when a small group of muscle cells in the wall of the left atrium starts to send out electrical impulses to the surrounding heart muscle cells. Explain how the control of heartbeat by the sinoatrial node can be disrupted by AF, resulting in rapid and irregular atrial contractions. Red blood cells are involved in the transport of oxygen and carbon dioxide in the blood. is a diagram representing the exchange of oxygen and carbon dioxide between a red blood cell in a capillary and a respiring cell. Some of the reactions that take place in the red blood cell are also shown. The diagram is not drawn to scale. capillary wall respiring cell CO2 4O2 Z Z endothelial cells CO2 + H2O 4O2 + Y red blood cell enzyme X H2CO3 carbonic acid HCO3 – hydrogencarbonate ion HbO8 + H+ oxyhaemoglobin H+ + basement membrane Identify enzyme X and molecule Y in . X Y The hydrogencarbonate ions shown in leave the red blood cell and are replaced by chloride ions. State why it is necessary for chloride ions to enter the red blood cell as hydrogencarbonate ions leave. Identify the aqueous environment, labelled Z in , that surrounds the respiring cell. Oxygen and carbon dioxide are also exchanged between blood capillaries and alveoli in the lungs. The gas exchange system has specialised cells to prevent harmful microscopic particles that are present in inhaled air from reaching the alveoli. These particles are associated with many respiratory diseases. Explain how specialised cells in the gas exchange system prevent harmful microscopic particles from reaching the alveoli.
9700_m22_qp_22
THEORY
2022
Paper 2, Variant 2
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Table 2.1 shows descriptions of three types of white blood cell. Complete Table 2.1 by stating the names of these three types of white blood cell. Table 2.1 description name of white blood cell A large cell that has a bean-shaped (kidney-shaped) nucleus. It can develop into a macrophage. A cell that has a large spherical nucleus and little cytoplasm. It responds to non-self antigens. A cell that has a lobed nucleus. It is phagocytic. Dromedary camels are classified in the family Camelidae and live in desert habitats of North Africa and Asia. In these hot, dry environments, dromedary camels can lose up to 30% of their body mass from dehydration, causing their blood to become more viscous . shows a drawing of red blood cells of a dromedary camel. is a drawing of human red blood cells. ×2000 ×2000 The llama is also classified in the family Camelidae. Llamas live in mountainous areas of South America, often at altitudes of 3500 m or higher. As the altitude above sea level increases, the air pressure decreases. The partial pressure of oxygen in the lungs of mammals at 3500 m is 6.4 kPa. shows the oxygen dissociation curve of adult human haemoglobin and adult llama haemoglobin. 0.0 2.0 4.0 6.0 8.0 partial pressure of oxygen / kPa 10.0 12.0 14.0 percentage saturation of haemoglobin with oxygen key adult llama haemoglobin adult human haemoglobin With reference to , explain how the differences between the oxygen dissociation curves for humans and llamas show that llamas are better adapted for living at high altitudes than humans. Sketch a curve on to show the effect of an increased carbon dioxide concentration on the percentage saturation of adult human haemoglobin with oxygen. Explain the importance of the Bohr shift in metabolically active organs, such as the liver.
9700_m24_qp_22
THEORY
2024
Paper 2, Variant 2
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Questions Discovered
241