Nutrition and Digestion：练习题

What is the name of the process by which food is moved through the esophagus by the rhythmic contraction of muscles?

In an experiment, 2 cm\(^3\) of saliva was added to a starch solution and kept at \(37^\circ\text{C}\). After 20 minutes, the mixture was tested with Benedict's solution and heated. What is the expected observation and the reason behind it?

The diagram below shows the human digestive system with various organs labeled. Which of the following correctly describes the functions of the organs labeled X (the liver) and Y (the pancreas)?

Organ X: Produces bile to emulsify fats.
Organ Y: Secretes digestive enzymes and neutralizes acidic chyme.

Which chemical is used to test for the presence of starch in a food sample, and what is the color change if starch is present?

The diagram shows a cross-section of the small intestine wall. What is the structural significance of the finger-like projections labeled X?

State the role of hydrochloric acid in the gastric juice produced by the stomach during the process of digestion.

Explain how the bile produced by the liver aids in the digestion of fats in the duodenum.

A student investigates the digestion of lipids in two test tubes. Test tube A contains oil and lipase. Test tube B contains oil, lipase, and bile salts. Explain why the contents of test tube B will likely turn acidic faster than test tube A.

(a) Name the three main types of food substances that must be digested before they can be absorbed into the human body.
(b) Explain two reasons why most food substances need to be digested before absorption can occur.

A student conducted an experiment to investigate the effect of temperature on the activity of amylase. She mixed starch solution with amylase and placed the test tubes in different water baths.
(a) Describe the chemical test used to confirm the presence of starch and state the expected color change if starch is present.
(b) Amylase is a type of chemical called an enzyme. Briefly explain the function of amylase in the human digestive system.
(c) If the experiment was conducted at \(80^{\circ}C\), predict whether starch would be broken down. Explain your answer.