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10 (a) A person with kidney disease may need kidney dialysis treatment - Edexcel - GCSE Biology - Question 10 - 2020 - Paper 1
Question 10
10 (a) A person with kidney disease may need kidney dialysis treatment. Figure 15 shows an experiment to show how a dialysis membrane works. (i) Describe the metho... show full transcript
Worked Solution & Example Answer:10 (a) A person with kidney disease may need kidney dialysis treatment - Edexcel - GCSE Biology - Question 10 - 2020 - Paper 1
Step 1
Describe the method that would be used to find out what is present in the solution in the beaker, after one hour.
Answer
To determine what is present in the solution in the beaker after one hour, the following method can be used:
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Sample Extraction: Collect a small sample of the solution from the beaker using a pipette or a syringe.
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Testing for Starch: Use iodine solution to test for the presence of starch. Add a few drops of iodine to the sample. A blue-black color indicates the presence of starch.
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Testing for Glucose: Use Benedict's test for glucose. To do this, mix the sample with Benedict's reagent in a test tube, then heat it in a water bath. A color change (green, yellow, or brick-red) indicates the presence of glucose.
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Observing Changes: Record any color changes observed during testing, and interpret these results to confirm the presence or absence of starch and glucose.
Step 2
Explain how this experiment represents a simple model of kidney dialysis treatment.
Answer
This experiment simulates kidney dialysis treatment by demonstrating the selective permeability of the dialysis membrane, akin to the filtration function of the kidneys.
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Permeability: The dialysis membrane allows certain molecules (like water and glucose) to pass through while preventing larger molecules (like starch) from doing so, mimicking how kidneys filter blood.
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Diffusion Process: Just as in kidney dialysis, where waste products diffuse out of the blood into the dialysis fluid, in this experiment, substances diffuse from the dialysis tube into the surrounding water or vice versa, simulating the exchange process in kidneys.
Step 3
Explain how substances are exchanged between the blood entering the nephron and the filtrate leaving the collecting duct.
Answer
Substances are exchanged in the nephron through processes of filtration, reabsorption, and secretion. The key structures involved include:
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Glomerulus: Blood enters the nephron through the afferent arteriole into the glomerulus, where high pressure facilitates the filtration of water, ions, glucose, and urea from the blood into the Bowman's capsule, forming the filtrate.
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Proximal Convoluted Tubule (PCT): Here, 65% of the filtrate is reabsorbed back into the blood, including vital substances like glucose, amino acids, and some ions via active transport.
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Loop of Henle: This structure creates a concentration gradient in the medulla, allowing for the reabsorption of water and some salts back into the bloodstream, concentrating the urine.
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Distal Convoluted Tubule (DCT): More regulation of ion balance and water reabsorption occurs here, as well as secretion of unwanted substances back into the filtrate.
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Collecting Duct: As the filtrate passes through the collecting duct, more water can be reabsorbed based on body needs, further concentrating the urine, with antidiuretic hormone (ADH) influencing this process.