8.2. Transport of oxygen and carbon dioxide
A subsection of Biology, 9700, through 8. Transport in mammals
Listing 10 of 241 questions
Cartilage is present in some parts of the gas exchange system to prevent collapse due to pressure changes during inhalation. State the parts of the gas exchange system in which cartilage is located. shows the changes that occur in atmospheric pressure and oxygen partial pressure as altitude changes. The highest altitude at which people live permanently is 5100 m. altitude / m atmospheric pressure / kPa oxygen partial pressure / kPa 10 000 Fig 3.1 With reference to : describe the effect of increasing altitude on both atmospheric pressure and the partial pressure of oxygen calculate the change in the atmospheric pressure when a person travels from sea level to an altitude of 3500 m. Show your working. answer When a person travels from 0 m (sea level) to a high altitude, gas exchange in the lungs is affected. A condition known as hypoxia results, where the body tissues do not receive an adequate oxygen supply. Explain how hypoxia occurs when a person ascends from sea level to a high altitude. At high altitudes, short-term responses by the body to hypoxia include: • a decrease in the volume of plasma in the blood • a decrease in the volume of blood pumped out of the heart per heart beat • an increase in the heart rate • an increase in the breathing rate. Suggest why a decrease in the volume of plasma in the blood may reduce the effects of hypoxia. Explain why an increase in the heart rate occurs in response to hypoxia. People with sickle cell anaemia have a form of haemoglobin that is unable to bind to oxygen efficiently. The cause of the condition is a mutation in the gene coding for the β-globin polypeptide of haemoglobin. Outline how this mutation can lead to an altered amino acid sequence of the β-globin polypeptide.
9700_s14_qp_22
THEORY
2014
Paper 2, Variant 2
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When haemoglobin in red blood cells travels through the capillaries of the lungs it binds with oxygen to form oxyhaemoglobin. When oxyhaemoglobin reaches respiring tissues, it dissociates to release oxygen. Explain what causes oxyhaemoglobin to dissociate readily in actively respiring tissues. When people move to high altitudes there is an increased production of red blood cells. Explain why more red blood cells are produced when people move to higher altitudes. Some people who move to live at high altitudes can develop chronic mountain sickness. One feature of this condition makes it difficult for the heart to pump blood around the body owing to the increased production of red blood cells. The EPAS1 gene codes for a type of protein called a transcription factor, which helps to regulate the transcription of genes involved in red blood cell production. Some people have a mutated version of this gene that prevents the over-production of red blood cells. Explain what is meant by transcription. Describe how a mutated version of the EPAS1 gene can cause a change in the transcription factor protein produced. Some transcription factors may prevent transcription. Suggest two ways in which they may do this. 1. 2.
9700_s14_qp_23
THEORY
2014
Paper 2, Variant 3
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Questions Discovered
241