21. The majority of the digestive enzymes are produced in the

A. pancreas.

B. stomach.

C. liver.

D. mouth.

22. Pepsin is active in the

A. mouth.

B. stomach.

C. small intestine.

D. large intestine.

23. Mucus production in the gastrointestinal tract

A. activates enzymes.

B. maintains the appropriate pH for enzyme action.

C. protects the lining of the GI tract from digestive action.

D. initiates the process of digestion.

24. Bile acts as a(an)

A. coagulant.

B. inhibitor.

C. enzyme.

D. emulsifier.

25. Which of the following statements best describes the enterohepatic circulation?

A. It is the movement of fat-soluble vitamins from intestine to liver.

B. It is the recycling of bile between intestine and liver.

C. It is the movement of all nutrients from intestine to liver.

D. None of the above relates to the enterohepatic circulation.

26. During the process of digestion the pH in the stomach is ________ the pH in the small intestine.

A. higher than

B. lower than

C. the same as

D. similar to but not the same as

27. Which of the following is true about bicarbonate ions?

A. They provide a favorable pH for enzyme action.

B. They neutralize acids.

C. They indirectly provide protection to the lining of the duodenum from the acidic effects of chyme.

D. All of the above are true.

28. Under normal conditions, the body absorbs up to ________ percent of the nutrients in food.

A. 97

B. 92

C. 87

D. 82

29. The process in the small intestine in which a cell forms a vesicle to surround and engulf a nutrient is called

A. passive diffusion.

B. facilitated diffusion.

C. active transport.

D. endocytosis.

30. In facilitated diffusion, what helps nutrients cross the membrane wall?

A. concentration gradient

B. carrier proteins

C. “cell drinking”

D. amino acids