9. Gas exchange
A section of Biology, 9700
Listing 10 of 240 questions
Some tissues of the gas exchange system include cells that are able to produce and secrete mucins. Mucins are stored in vesicles in these cells, ready for secretion. Once outside the cell, mucins adsorb water to form mucus. Name the structures in the gas exchange system that produce and secrete mucins. Mucins are described as glycosylated proteins. The process of glycosylation involves the addition of sugar components after polypeptides are synthesised. Suggest one location in the cell where glycosylation of mucin could occur. The processes that occur in the production and secretion of mucins are listed. translation exocytosis glycosylation transcription Complete Table 2.1 by writing the processes in the correct order in which they would take place. Table 2.1 first process second process third process fourth process Chloride ions move out of the mucin-producing cells at the same time as mucin is secreted. Suggest and explain how the exit of chloride ions helps the formation of mucus from mucin. The gas exchange system includes some cells that are able to divide by mitosis. Explain why it is important to have these cells in the gas exchange system.
9700_s19_qp_22
THEORY
2019
Paper 2, Variant 2
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The cilia of ciliated epithelial cells show variation in length, within an individual and between different individuals. Samples of ciliated epithelial tissue were removed from the airways of healthy people and the mean cilia length for each individual was calculated. The people in the study formed two groups: • people who were exposed to a harmful environmental factor • people who were not exposed to a harmful environmental factor. The results are shown in . mean length of cilia / μm percentage frequency Key: people not exposed to a harmful environmental factor people exposed to a harmful environmental factor Name the type of variation shown for mean cilia length in each group of people in . Suggest two harmful environmental factors that people might have been exposed to that could explain the difference between the two curves in . The development and final length of cilia of epithelial cells is controlled by many genes. summarises the interactions of some of these genes. The arrows represent the genes being switched on. regulatory gene A regulatory gene B 6 structural genes 2 structural genes 11 structural genes regulatory gene C With reference to , explain how genes such as A, B and C are able to switch on other genes. Describe how microarray analysis can be used to identify the genes switched on by the product of gene C. Microarray analysis has shown that ciliated epithelial cells and other epithelial cells in the airways express genes that code for receptor proteins on cell surface membranes. These receptor proteins detect specific chemicals. When the receptor proteins bind to specific chemicals, this causes coughing, constriction of the airways and an increase in cilia activity. In people who have asthma, the response can be severe and life-threatening. Suggest how knowledge of the genes for these receptor proteins could help in the treatment of asthma.
9700_s19_qp_43
THEORY
2019
Paper 4, Variant 3
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A student was asked to describe the differences between four microscope slides of sections taken from different parts of the gas exchange system. slide 1 not present: cartilage, glands present: few goblet cells, ciliated epithelial cells, smooth muscle slide 2 present: incomplete cartilage rings, glands, goblet cells, ciliated epithelial cells, smooth muscle slide 3 not present: cartilage, glands, goblet cells, smooth muscle present: squamous epithelial cells slide 4 present: plates of cartilage, glands, goblet cells, ciliated epithelial cells, smooth muscle Which is the correct identification of the parts of the gas exchange system?
9700_s20_qp_13
MCQ
2020
Paper 1, Variant 3
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shows the site of gas exchange in the mammalian lung. red blood cells elastic fibres W X Y State two ways in which carbon dioxide is transported in the blood. Table 4.1 shows the partial pressures of oxygen (pO2) and carbon dioxide (pCO2) at locations W, X and Y in . Table 4.1 partial pressure locations within tissue W X Y pO2 / kPa 13.87 5.33 13.87 pCO2 / kPa 5.33 6.00 5.55 With reference to and Table 4.1, describe the exchanges that occur as blood flows from X to Y. Elastic fibres are present in tissues at the site of gas exchange in the lungs. Describe the roles of elastic fibres in the gas exchange system and in the cardiovascular system. Scientists in Peru investigated the effect of moving from sea level to high altitude on the composition of blood. The scientists studied 10 students. Each student had lived at sea level since birth and then moved to live in the Andes at a height of 4500 metres above sea level. The scientists took samples of blood from each student before they moved to live at high altitude. The scientists took further blood samples at intervals after the students had moved to high altitude. The relative proportions of red blood cells and plasma in each sample were determined. The total volume of blood for each student was also determined at each sampling time. As the students were all of different body mass, the total volumes were converted to a volume per kg of body mass (cm3 kg–1). shows for each sampling time: • the mean volume of blood per kg of body mass • the proportions of red blood cells and plasma. time / months after moving to high altitude red blood cells plasma Key mean volume of blood per kg of body mass / cm3 kg–1 7 to 8 5 to 6 3 to 4 1 to 2 0 (at sea level) The percentage of mean blood volume that is represented by red blood cells for the samples taken at sea level is 48%. Calculate the percentage of mean blood volume that is represented by red blood cells at 5 to 6 months after living at high altitude. Show your working and give your answer to the nearest whole number. answer = % Describe and explain the results in .
9700_s20_qp_21
THEORY
2020
Paper 2, Variant 1
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Collagen is a major component of the cartilage found in some of the structures of the human gas exchange system. Cells that synthesise and secrete the components of cartilage are known as chondrocytes. is a transmission electron micrograph of a chondrocyte. With reference to , explain two features of the chondrocyte that show how the cell is adapted to its function. Describe the distribution of cartilage in the human gas exchange system. Outline the function of cartilage in the human gas exchange system. shows part of the primary structure of a collagen polypeptide. gly glu arg gly glu gln gly ala pro gly Name the type of covalent bond formed between the amino acids shown in . shows the molecular structure of the amino acid glycine . N H H C C O H O H H With reference to and and the function of collagen, explain how the structure of a collagen polypeptide makes it suitable to form a collagen molecule.
9700_s20_qp_22
THEORY
2020
Paper 2, Variant 2
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is a photomicrograph of a section through two different types of blood vessels, X and Y. X Y Name the two types of blood vessel shown by X and Y in . X Y State the reasons for your identification of the type of blood vessel shown by Y in . Tissue fluid and lymph are formed when blood arrives in the capillary networks of body tissues. Explain why tissue fluid is more similar to blood plasma than it is to blood. Explain why the tissue fluid formed after blood arrives in the capillary network has a higher concentration of amino acids than the newly formed lymph draining away from the network. The trachea, bronchi and bronchioles in the gas exchange system require a supply of glucose and oxygen from the blood for the functioning of smooth muscle. Outline the function of smooth muscle in the gas exchange system.
9700_s20_qp_23
THEORY
2020
Paper 2, Variant 3
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Questions Discovered
240