tymoczko3e

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PROBLEMS

Question 14.1

1. Fast and furious. Match each term with its description. ✓ 1

Digestion Cholecystokinin Zymogens Enteropeptidase α-Amylase Emulsion Bile salts Chylomicron K⁺/H⁺ ATPase Lipase	Activates trypsin Proenzymes Water–lipid droplets Digests carbohydrates The conversion of food into simple biochemicals Results in the secretion of digestion enzymes Acidifies the stomach Transports dietary lipids from intestinal cells to elsewhere in the body Hydrolyzes lipids Inserts into emulsions to facilitate lipase action
Correct Matches:

Question 14.2

2. Necessary but not sufficient. Why is digestion required for fuel metabolism even though no useful energy is harnessed in the process?

Question 14.3

3. Mother knows best. When your mother told you to chew your food well, she had your best biochemical interests at heart. Explain. ✓ 1

Question 14.4

4. Accessibility matters 1. Dietary proteins must be denatured for efficient digestion. Why? ✓ 1

Question 14.5

5. Deconstruction. Outline how starch and glycogen are digested. ✓ 1

Question 14.6

6. Safeguard. Trypsin inhibitor is a pancreatic polypeptide that binds trypsin with very high affinity, preventing it from digesting proteins. Why might a lack of trypsin inhibitor cause pancreatitus (inflammation of the pancreas)? ✓ 2

Question 14.7

7. Not too al dente. The digestion of macaroni is more efficient after the pasta has been heated in water. Why? ✓ 1

Question 14.8

8. Phase problems. What properties of lipids make their digestion more complicated than that of carbohydrates and proteins? How are lipids made accessible for digestion? ✓ 1

Question 14.9

9. Accessibility matters 2. Why is emulsification required for efficient lipid digestion? ✓ 1

Question 14.10

10. Humors are necessary. How would a lack of bile salts affect digestion?

Question 14.11

11. Doing their part. What is the role of micelles in lipid digestion?

Question 14.12

12. Precautions. Why are most digestive enzymes produced as zymogens? ✓ 2

Question 14.13

13. Dual roles. What two biochemical roles does CCK play? ✓ 2

Question 14.14

14. Electrolyte disturbance. Hyponatremia, or low blood sodium, results from excessive losses of fluid and sodium, or from dilution of sodium levels with excess fluid. Hyponatremia is treated by oral rehydration therapy, the administration of a solution of glucose and sodium. Suggest one role for the sodium.

Challenge Problem

Question 14.15

15. Zymogen activation. When very low concentrations of pepsinogen are added to an acidic medium, how does the halftime of activation depend on zymogen concentration? ✓ 2

Selected Readings for this chapter can be found online at www.whfreeman.com/tymoczko3e.

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