8.2. Transport of oxygen and carbon dioxide
A subsection of Biology, 9700, through 8. Transport in mammals
Listing 10 of 241 questions
and are photomicrographs showing the distribution of tissues in the lungs. is a photomicrograph of a section through part of the lungs. is a high-power view of the area indicated on . A B section enlarged in C D A State the names of the tissues A, B and D. A B D Describe the role of the glands labelled C in in maintaining the health of the gas exchange system. Hyperventilation occurs when a person breathes too fast or too deeply. The effects of hyperventilation are: • a decrease in the partial pressure of carbon dioxide in alveolar air • an increase in the pH of the blood. shows the change in the oxygen dissociation curve as a result of hyperventilation. percentage saturation of haemoglobin with oxygen partial pressure of oxygen (pO2) / kPa Key pH 7.4 pH 7.7 State the percentage saturation of haemoglobin at a pO2 of 4.0 kPa. pH = 7.7 kPa pH = 7.4 kPa Use the information in to state and explain the effect of hyperventilation on the supply of oxygen to the respiring tissues.
9700_s22_qp_21
THEORY
2022
Paper 2, Variant 1
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The enzyme carbonic anhydrase has been found in a wide range of organisms and acts as a catalyst in many tissues. Studies have shown that there are differences in the protein structure of the enzyme and differences in the number and organisation of introns and exons of the gene coding for the enzyme. All carbonic anhydrase enzymes catalyse the same reversible reaction, shown in . carbonic anhydrase CO2 H2O + carbon dioxide hydrogen ions water X Y H2CO3 HCO3 – H+ + With reference to , name X and Y. X Y Carbonic anhydrase enzymes can have different primary structures. Suggest how all carbonic anhydrase enzymes can catalyse the same reaction, even though they have different primary structures. Genes coding for proteins in eukaryotes consist of introns and exons. Outline the similarities and differences between the introns and the exons of genes coding for proteins such as carbonic anhydrase. All mammals have the same type of carbonic anhydrase, known as α-carbonic anhydrase. Many different forms, or isoforms, of α-carbonic anhydrase have been identified in mammals. There are 15 isoforms of α-carbonic anhydrase (CA) in humans. Cells of different tissues have one or more isoforms. Within cells the isoforms may be in different locations. Red blood cells contain two isoforms, CA1 and CA2. Suggest the location of CA1 and CA2 in red blood cells and give a reason for your answer. Isoform CA6 forms part of human breast milk. Mammary gland cells package CA6 in Golgi vesicles for release from the cells. Name the transport mechanism associated with CA6 secretion. Human CA isoforms in some epithelial cells in the eye have a role in the formation of the clear fluid of the eye known as aqueous humour. Overactivity of the enzyme may lead to a harmful increase of pressure within the eye and cause a condition known as glaucoma. Acetazolamide is a therapeutic drug that can be used in the treatment of glaucoma. It acts as a reversible non-competitive inhibitor. Describe the mechanism of action of acetazolamide as a reversible non-competitive inhibitor of carbonic anhydrase.
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THEORY
2022
Paper 2, Variant 2
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is a longitudinal section of a capillary in muscle tissue as viewed with a transmission electron microscope. magnification ×2000 State the evidence, visible in , that identifies the cells inside the capillary as red blood cells. Explain how the structure of the capillary wall is related to its functions. is a diagram showing some of the events that occur as blood flows through a capillary in a respiring tissue. CO2 CO2 CO2 CO2 CO2 O2 O2 CO2 + H2O H2O red blood cell O2 O2 O2 O2 O2 carbonic anhydrase H2CO3 HCO3 – HCO3 – H+ cells of respiring tissue An increase in respiration results in an increase in the carbon dioxide concentration in the blood and the release of more oxygen from red blood cells to tissues. Explain how an increase in carbon dioxide in the blood leads to the release of more oxygen from red blood cells. Chloride ions are a constituent of blood plasma. The concentration of chloride ions in the plasma of deoxygenated blood is between 2–4 mmol dm–3 lower than in the plasma of oxygenated blood. Explain why the concentration of chloride ions in the blood plasma of deoxygenated blood is lower than in the plasma of oxygenated blood.
9700_s23_qp_21
THEORY
2023
Paper 2, Variant 1
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Blood contains white blood cells and red blood cells. is a photomicrograph showing different types of blood cell. X Y Z Identify cell X and cell Y in . X Y The width of one of the cells in is represented by the line Z. The actual width of cell Z is 8 µm. Calculate the magnification used to produce the image shown in . Write down the formula you will use to make your calculation. formula magnification = x Carbonic anhydrase is an enzyme found in red blood cells. Describe how carbonic anhydrase is involved in the release of oxygen from red blood cells at respiring tissues. Sulfonamide is a competitive inhibitor of carbonic anhydrase. shows the effect of increasing substrate concentration on the rate of the reaction catalysed by carbonic anhydrase. Sketch a curve on to show the effect of sulfonamide on the rate of reaction catalysed by carbonic anhydrase. rate of reaction substrate concentration
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THEORY
2023
Paper 2, Variant 3
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Questions Discovered
241