Digestion and absorption：練習題

During digestion and absorption, the concentration of sodium ions in the ileum lumen is higher than inside the epithelial cells. Which of the following is the direct energy source that drives the co-transport of amino acids into the epithelial cells?

In digestion and absorption, the transport of galactose from the lumen of the ileum into the epithelial cells occurs via a specific mechanism. Which of the following is required for this process to be successful?

Why is it physiologically advantageous for disaccharidases, such as maltase, to be membrane-bound in the ileum rather than secreted as soluble enzymes into the gut lumen?

What is the specific role of micelles during the absorption of the products of lipid digestion in the ileum?

During the digestion of proteins, what is the functional advantage of exopeptidases acting after endopeptidases?

In the process of digestion and absorption, explain how the hydrolysis of triglycerides differs from the absorption of the resulting monoglycerides and fatty acids in terms of crossing the ileum epithelial cell membrane.

Explain how the formation of micelles facilitates the absorption of the products of lipid digestion by the epithelial cells of the ileum.

During the digestion and absorption of carbohydrates, explain how the presence of membrane-bound disaccharidases in the ileum provides a more efficient mechanism for nutrient uptake than if these enzymes were secreted into the lumen.

The digestion of complex carbohydrates and proteins requires the coordinated action of several enzymes.

a) Describe the role of amylase and membrane-bound disaccharidases in the complete digestion of starch. (2 points)
b) Explain the co-transport mechanism by which amino acids are absorbed from the lumen of the ileum into the epithelial cells. Mention the role of sodium ions and ATP. (4 points)

Digestion involves the hydrolysis of large biological molecules into smaller units that can be absorbed across cell membranes.

a) Name the specific enzymes responsible for the hydrolysis of proteins and identify where membrane-bound dipeptidases are located in the digestive system. (2 points)
b) Describe the physical and chemical roles of bile salts in the digestion of lipids. (2 points)
c) Explain how the concentration gradient of sodium ions is maintained to allow the co-transport of glucose from the ileum into the epithelial cells. (1 point)