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To study lipid digestion, a scientist placed a tube into the gut of a healthy 20-year-old man - AQA - A-Level Biology - Question 2 - 2020 - Paper 1
Question 2
To study lipid digestion, a scientist placed a tube into the gut of a healthy 20-year-old man. The end of the tube passed through the stomach but did not reach as fa... show full transcript
Worked Solution & Example Answer:To study lipid digestion, a scientist placed a tube into the gut of a healthy 20-year-old man - AQA - A-Level Biology - Question 2 - 2020 - Paper 1
Step 1
Use your knowledge of lipid digestion to explain the differences in the results for samples A and B shown in Table 1.
Answer
In sample A, the concentration of triglycerides is 0.6 mg cm³, while in sample B, it is 0.2 mg cm³. The decrease in triglycerides from sample A to sample B is indicative of the action of lipase, which breaks down triglycerides into fatty acids and glycerol. Consequently, the concentration of fatty acids increases from 2.7 mg cm³ in sample A to 3.3 mg cm³ in sample B, aligning with the expected outcome of lipid digestion where triglycerides are hydrolyzed, resulting in increased fatty acid levels.
Step 2
Explain why.
Answer
The samples were heated to 70 °C for 10 minutes to denature the enzyme lipase. This denaturation is essential to halt any ongoing digestive processes and prevent any further breakdown of lipids after the samples are collected. Without denaturation, lipase could continue to act on any remaining lipids, thus interfering with accurate analysis of the samples.
Step 3
Describe the role of micelles in the absorption of fats into the cells lining the ileum.
Answer
Micelles play a crucial role in the absorption of fats in the ileum as they help solubilize lipids. They do this by incorporating bile salts that make fatty acids more soluble in water. Micelles facilitate the transport and release of fatty acids to the epithelial cells lining the ileum, enhancing their concentration at the surface of these cells. This increased concentration aids in the diffusion of fatty acids into the cells. Moreover, micelles help in maintaining a gradient that favors absorption, ensuring efficient uptake of lipids.