AP Biology : Understanding Stomach Enzymes and Cell Types

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #1 : Digestive Physiology

Which compound is correctly matched to the type of cell that produces it?

Possible Answers:

Parietal cells secrete pepsinogen

Parietal cells secrete mucous

Chief cells secrete pepsin

Goblet cells secrete hydrochloric acid

Chief cells secrete pepsinogen

Correct answer:

Chief cells secrete pepsinogen

Explanation:

The stomach contains several cell types, each with a specific mechanism of action.

Chief cells produce pepsinogen, which is converted to pepsin by hydrochloric acid in the stomach. Parietal cells produce hydrochloric acid, allowing this conversion. Goblet cells produce the mucous lining of the stomach that protects the stomach epithelium from damage from the acidic environment of the gastric lumen.

Example Question #22 : Digestive System

Which enzyme is correctly paired with the macromolecule that it digests?

Possible Answers:

Peptidase catabolizes proteins

Lipase catabolizes carbohydrates

Amylase catabolizes proteins

Peptidase catabolizes lipids

Correct answer:

Peptidase catabolizes proteins

Explanation:

Amylase is an enzyme found in saliva and the small intestine that breaks starches down into sugars. The correct pairing for amylase would be carbohydrates.

Peptidases break peptide bonds, which are what hold amino acids together in proteins. Different peptidases are found in the stomach (pepsin) and the small intestine (trypsin). The correct pairing for peptidase is proteins.

Lipase is an enzyme that catalyzes the hydrolysis of triglycerides into free fatty acids in the small intestine. The correct pairing for lipase would be fats or lipids.

Example Question #3 : Digestive Physiology

Which of the following is most closely linked to the activation of pepsinogen?

Possible Answers:

G cell

Chief cell

Goblet cell

Parietal cell

Correct answer:

Parietal cell

Explanation:

Pepsinogen is an inactive enzyme (zymogen) that is released by chief cells into the stomach lumen. In order to be activated, the enzyme must be at a very low pH. This is accomplished by hydrochloric acid, which is released by the parietal cells in response to stimulation by gastrin. Parietal cells are, thus, most closely linked to the activation of pepsinogen.

Gastrin is released by G cells. Goblet cells secrete the mucous lining of the stomach.

Example Question #1 : Digestive Physiology

Which of the following cells in the stomach is necessary for the activation of pepsinogen?

Possible Answers:

Parietal cells

Goblet cells

G cells

Chief cells

None of these

Correct answer:

Parietal cells

Explanation:

Pepsinogen is released by chief cells in the stomach, and is the zymogen form of pepsin. Pepsinogen requires an acidic environment in order to be converted to pepsin. Parietal cells release hydrochloric acid into the stomach lumen, thus activating the enzyme.

G cells and goblet cells secrete gastrin and mucous, respectively, into the stomach.

Example Question #1 : Understanding Stomach Enzymes And Cell Types

Which stomach cell type secretes gastrin?

Possible Answers:

Parietal cells

Chief cells

G cells

Goblet cells

Oxyntic cells

Correct answer:

G cells

Explanation:

G cells secrete the hormone gastrin. Gastrin further stimulates stomach acid secretions via parietal (oxyntic) cells. Chief cells secrete pepsinogen, the inactive form of the enzyme pepsin, which degrades proteins. Goblet cells secrete mucous to protect the cells of the stomach from the acid.

Example Question #6 : Digestive Physiology

Which of the following enzymes becomes activated in a low pH environment?

Possible Answers:

Gastrin

Lysozyme

Trypsinogen

Pepsinogen

Chymotrypsinogen

Correct answer:

Pepsinogen

Explanation:

The only one of the enzymes listed that becomes activated in the presence of an acidic (low pH) environment is pepsinogen. When activated, pepsinogen forms into pepsin which occurs in the stomach because of the  (hydrochloric acid) present. Enzymes and/or hormones that have the suffix -ogen, or the prefix pro- are known as zymogens or prohormones, which are not active. Different environments/molecules activate these enzymes and proteins. This method of activation allows for more rapid usage, rather than having to synthesize these molecules from scratch when they are needed.

Example Question #4 : Understanding Stomach Enzymes And Cell Types

How is the zymogen protease activated in the stomach?

Possible Answers:

It reacts with the hydrochloric acid to become pepsin

It binds to chief cells to become pepsin

It is active upon secretion

It binds to parietal cells to become pepsin

It gets cleaved by trypsin to become catalytically active

Correct answer:

It reacts with the hydrochloric acid to become pepsin

Explanation:

To become active, hydrochloric acid in the stomach reacts with pepsinogen to make pepsin.

Example Question #8 : Digestive Physiology

In the stomach, the __________ cell secretes __________.

Possible Answers:

chief cell . . . hydrochloric acid

parietal cell . . . hydrochloric acid

chief cell . . . pepsin

chief cell . . . pepsinogen

parietal cell . . . pepsinogen

Correct answer:

chief cell . . . pepsinogen

Explanation:

The chief cells of the stomach secrete the proteolytic zymogen pepsinogen. This zymogen then becomes activated as pepsin in the stomach.

Example Question #9 : Digestive Physiology

The __________ cell secretes __________ in order to reduce the pH of the stomach to increase food digestion.

Possible Answers:

parietal . . . hydrochloric acid

parietal . . . hydrofluoric acid

chief . . . carbonic acid

parietal . . . bile

chief . . . hydrochloric acid

Correct answer:

parietal . . . hydrochloric acid

Explanation:

The parietal cells of the stomach begin secreting hydrochloric acid even upon the smell of food (before consumption takes place) in order to begin the digestion process. These cells are common targets of antacid medications to reduce acid reflux. 

Example Question #5 : Understanding Stomach Enzymes And Cell Types

The high concentration of __________ present in the stomach activates pepsinogen, allowing it to become active pepsin.

Possible Answers:

undigested food

ATP

hydrochloric acid

bile

saliva

Correct answer:

hydrochloric acid

Explanation:

Hydrochloric acid, produced by the parietal cells of the stomach, activates the zymogen pepsinogen. 

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