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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
2.1 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, taken 45 minutes after the meal, the concentration of fatty acids is 2.7 mg cm⁻³, while in sample B, taken 75 minutes after the meal, it is 3.3 mg cm⁻³. The concentration of triglycerides in sample A is 0.6 mg cm⁻³, but in sample B, it drops to 0.0 mg cm⁻³.
This indicates that triglycerides are progressively hydrolyzed by lipase into fatty acids and glycerol over time. The increase in fatty acids correlates with the time after the meal, suggesting that lipase activity is effective in breaking down triglycerides into fatty acids, leading to the observed increase in fatty acid concentration. Thus, the decrease in triglycerides and the increase in fatty acids demonstrate the enzymatic action of lipase and the hydrolysis of triglycerides.
Step 2
2.2 Explain why.
Answer
The scientist heated the samples to 70 °C for 10 minutes to denature the enzymes, including lipase. Denaturation alters the structure of the enzyme, rendering it inactive. This step ensures that no further digestion or hydrolysis of the fats occurs after the samples are collected, allowing for accurate measurement of lipid concentrations.
Step 3
2.3 Describe the role of micelles in the absorption of fats into the cells lining the ileum.
Answer
Micelles are structures that include bile salts and fatty acids, which facilitate the absorption of fats in the ileum. They help to solubilize fatty acids in the aqueous environment of the intestine, effectively transporting them to the intestinal cell membrane. Additionally, micelles bring fatty acids closer to the cells lining the ileum, where they can diffuse across the membrane. Once inside, fatty acids can be processed and utilized by the cells. Therefore, micelles play a crucial role in increasing the efficiency of fat absorption.