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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, taken 45 minutes after the meal, the concentration of fatty acids is 2.7 mg cm⁻³, while the concentration of triglycerides is 0.6 mg cm⁻³. This indicates that lipase is acting on the triglycerides, breaking them down into fatty acids and glycerol. By 75 minutes in sample B, the concentration of fatty acids has increased to 3.3 mg cm⁻³ while the concentration of triglycerides has dropped to 0.0 mg cm⁻³. This suggests that almost all triglycerides have been hydrolyzed, resulting in a higher concentration of fatty acids. The increase in fatty acids is due to the hydrolysis of triglycerides, showing that lipid digestion is occurring effectively over time.
Step 2
Explain why.
Answer
The scientist heated the samples to 70 °C to denature the enzymes, particularly lipase, which would inhibit further digestion and hydrolysis of fats. This ensures that the concentrations measured reflect the state at the time of collection without additional enzymatic action altering the results.
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 lipid absorption by including bile salts and fatty acids. They facilitate the efficient transport of fatty acids to the epithelial cells lining the ileum. Micelles are soluble in water, allowing them to bring and release fatty acids to the intestinal lining. Once near the intestinal cells, fatty acids can diffuse into the cells, where they may be further processed before entering the lymphatic system. This process enhances the uptake of fats, allowing for effective absorption into the body.