To investigate the kinetics of lipid digestion, a researcher set up a simulated duodenal bioreactor containing a constant concentration of lipase and bile salts. A lipid emulsion containing triglycerides was introduced at time t=0t = 0t=0. Small samples of the reaction mixture were withdrawn at specific time intervals.
The concentrations of triglycerides and free fatty acids in the samples were determined and recorded in Table 1.
Table 1
| Sample | Time of collection / min\text{min}min | Concentration of fatty acids / mg cm−3\text{mg cm}^{-3}mg cm−3 | Concentration of triglycerides / mg cm−3\text{mg cm}^{-3}mg cm−3 |
|---|---|---|---|
| X | 15 | 1.2 | 2.4 |
| Y | 45 | 4.8 | 0.0 |
Use your knowledge of lipid digestion to explain the differences in the concentrations of triglycerides and fatty acids between Sample X and Sample Y.
Immediately upon withdrawing each sample from the bioreactor, the researcher heated it to 90∘C90^\circ\text{C}90∘C for 10 minutes before analysis. Explain why this step is necessary.
Explain how micelles facilitate the absorption of fatty acids into the epithelial cells lining the small intestine.
12 exam-style questions on AQA A Level Biology Digestion and absorption, covering Digestion and absorption. Each one has a worked solution and a mark scheme showing where the marks go.