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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 the contents of the solution in the beaker after one hour, a sample can be taken from the beaker and tested using iodine solution. Iodine will turn blue-black in the presence of starch, indicating its presence in the solution. Another method is to use Benedict's test for glucose, where the solution is heated with Benedict's reagent; a color change will indicate the presence of glucose. The observations from these tests will reveal what substances have passed through the dialysis membrane.
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 by demonstrating the selective permeability of the dialysis membrane. Just as the dialysis membrane allows certain substances like water and small solutes to pass while retaining larger molecules, the kidneys filter blood to regulate the composition of bodily fluids. The experiment mimics the essential function of dialysis, facilitating the removal of waste products from the blood while retaining essential metabolites.
Step 3
Explain how substances are exchanged between the blood entering the nephron and the filtrate leaving the collecting duct.
Answer
In the nephron, blood enters through the afferent arteriole into the glomerulus, where filtration occurs. During this process, small molecules such as water, glucose, and ions pass through the glomerular membrane into Bowman's capsule, forming the filtrate. Larger molecules, such as proteins and blood cells, remain in the bloodstream.
In the renal tubule, reabsorption occurs: glucose and certain ions are reabsorbed into the bloodstream from the filtrate via active transport in the proximal convoluted tubule. In contrast, waste products like urea remain in the filtrate.
Ultimately, filtrate flows into the collecting duct, where further adjustments occur based on the body’s needs, with water reabsorption regulated by antidiuretic hormone (ADH). This process ensures that waste is excreted efficiently while retaining essential substances in the blood.