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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, a simple qualitative test can be performed. First, start by taking a sample of the solution. Next, use test strips or reagents specific for starch and glucose. For starch, iodine solution can be employed; if the sample turns blue-black, starch is present. For glucose, Benedict's reagent can be used; by heating the solution with the reagent, a color change – from blue to green/yellow/orange/red, depending on the concentration – would indicate the presence of glucose. This method effectively identifies the substances present in the solution.
Step 2
Explain how this experiment represents a simple model of kidney dialysis treatment.
Answer
This experiment serves as a simple model of kidney dialysis treatment by mimicking the selective permeability of the dialysis membrane. In kidney dialysis, waste products like urea and excess salts need to be removed from the blood, while essential components like glucose should remain in the bloodstream. The dialysis membrane allows certain molecules to pass through while blocking others, similar to how nephron membranes function in a kidney. The experiment's setup, with the solution in the dialysis tube, represents the patient's blood, showcasing how it interacts with the dialysate to remove waste after a set duration.
Step 3
Explain how substances are exchanged between the blood entering the nephron and the filtrate leaving the collecting duct.
Answer
Substances are exchanged between the blood entering the nephron and the filtrate leaving the collecting duct through various processes that occur in different parts of the nephron. Initially, blood enters the nephron through the glomerulus, where filtration happens due to high pressure. Here, small solutes, including water, salts, glucose, and waste products, pass into the Bowman’s capsule as filtrate. As this filtrate moves through the proximal convoluted tubule, reabsorption occurs, where useful substances like glucose and essential ions are transported back into the bloodstream. In the loop of Henle, the counter-current mechanism helps concentrate urine by allowing water to be reabsorbed in the descending limb and salts in the ascending limb. Finally, after passing through the distal convoluted tubule and the collecting duct, further adjustments of water and solute levels occur under hormonal control before the remaining filtrate exits as urine.