MCAT Biology : Digestive Enzymes and Cell Types

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #52 : Digestive System

Autodigestion of the stomach mucosal lining is prevented by which type of stomach cells?

Possible Answers:

G cells

Enterochromaffin-like (ECL) cells

D cells

Goblet cells

Correct answer:

Goblet cells

Explanation:

Goblet cells secrete a thick layer of mucous to prevent autodigestion of the stomach wall by enzymes secreted into the lumen, such as pepsin, and the low pH of the stomach contents. D cells secrete somatostatin to prevent gastric acid secretion, G cells secrete gastrin to promote acid secretion into the gastric lumen, and enterochromaffin-like (ECL) cells secrete histamine to promote acidification of the gastric lumen.

Example Question #11 : Digestive Enzymes And Cell Types

Which of the following cell types is known to secrete the peptide hormone that stimulates parietal cells to secrete hydrochloric acid?

Possible Answers:

G cells

Parietal cells

Mucous cells

Chief cells

Correct answer:

G cells

Explanation:

G cells secrete the large peptide hormone gastrin, which travels through blood to stimulate parietal cells to secrete hydrochloric acid. 

Mucous cells produce mucus to protect the epithelial lining of the stomach from the harsh acidic environment. Chief cells are found in the exocrine glands and secrete pepsinogen, which is activated by the low pH of the stomach to become pepsin. Pepsin catalyzes the breakdown of protein into peptides. 

Example Question #561 : Biology

Which process of digestion incorrectly pairs the enzyme or compound with its function in the small intestine?

Possible Answers:

Lipase digests fat

Peptidase digests protein

Amylase digests starch

HCO3- lowers the pH in the intestine

Correct answer:

HCO3- lowers the pH in the intestine

Explanation:

During digestion, the small intestine plays a major role in absorption and digestion of compounds. Because the contents of the stomach are extremely acidic, bicarbonate serves to neutralize hydrochloric acid, and raises the pH to an optimal level at which the enzymes can break down food.

Amylase is present in both saliva and the small intestine and breaks down starches and carbohydrates. Peptidase disrupts peptide bonds and digests proteins into amino acids. Lipase acts to hydrolyze lipids.

Example Question #52 : Digestive System

Stool testing determined that an individual has steatorrhea (excess fat in stool). A deficiency in which of the following could cause this problem?

Possible Answers:

Amylase

Trypsin

Lipase

Pepsin

Chymotrypsin

Correct answer:

Lipase

Explanation:

Lipase is the correct answer because it is the enzyme that is responsible for digesting fats in the small intestine. Trypsin, chymotrypsin, and pepsin digest protein. Amylase digests carbohydrates.

Example Question #553 : Systems Biology And Tissue Types

Which enzyme, released from the duodenum, stimulates the pancreas to release bicarbonate from its acinar cells?

Possible Answers:

Cholecystokinin

Trypsin

Secretin

Gastrin

Correct answer:

Secretin

Explanation:

Secretin is released from the duodenum in response to an influx of chyme, containing digested food and stomach acid, from the antrum of the stomach. In order not to damage the walls of the small intestine, the pancreatic acinar cells produce and secrete bicarbonate to mediate the pH of the chyme entering the small intestine. Secretin stimulates this release of bicarbonate from the pancreatic cells.

Gastrin stimulates acid secretion in the stomach, trypsin breaks down amino acids, and cholecystokinin increases contraction of the gallbladder to expel bile salts into the lumen of the duodenum through the sphincter of Oddi.

Example Question #52 : Digestive System

Which answer choice incorrectly matches an enzyme to the environment in which it works?

Possible Answers:

Lipase—acidic

Pepsin—acidic

Gastrin—acidic

Carboxypeptidase—basic

Trypsin—basic

Correct answer:

Lipase—acidic

Explanation:

Pepsin and gastrin are secreted into the acidic environment of the stomach, while lipase, trypsin, and carboxypeptidase are secreted into the basic environment of the small intestine. Acidic chyme from the stomach must be neutralized in the duodenum before the enzymes in the small intestine can begin digestion, creating the basic environment for these enzymes to function.

Lipase does not function in an acidic environment.

Example Question #112 : Excretory And Digestive Systems

Which one of the following digestive enzymes is NOT produced by the pancreas?

Possible Answers:

Chymotrypsin

Lipase

Trypsinogen

Carboxypeptidase

Pepsin

Correct answer:

Pepsin

Explanation:

Pepsin is a protease that is secreted by the chief cells located in the stomach. All of the other choices are digestive enzymes secreted by the pancreas. Lipase helps to digest fats, carboxypeptidase and chymotrypsin both break down proteins, and trypsinogen is a zymogen of trypsin.

Example Question #12 : Digestive Enzymes And Cell Types

Which of these enzymes would result in the biggest loss of digestion, if absent from the small intestine?

Possible Answers:

Trypsin

Pancreatic amylase

Chymotrypsin

Pancreatic lipase

Correct answer:

Trypsin

Explanation:

Trypsin is created by the pancreas, and is responsible for the degradation of proteins in the lumen of the small intestine. More importantly, activated trypsin activates all of the other enzymes present in the small intestine. If trypsin is absent, virtually no digestion would take place.

Example Question #551 : Systems Biology And Tissue Types

The pancreas is responsible for secreting which enzyme?

Possible Answers:

Lipase

Gastrin

Pepsin

Pepsinogen

Correct answer:

Lipase

Explanation:

The pancreas is responsible for secreting both lipase and amylase, which are needed to break down fats and starches, respectively. The pancreas is stimulated to release its respective enzymes about two to three hours after a fatty or carbohydrate-rich meal. These enzymes enter the duodenum through the ampulla of vater. In the duodenum, ingested fats and sugars are broken down to be absorbed later in the jejunum.

Gastrin is released by G cells and stimulates the release of hydrochloric acid in the stomach. Chief cells release pepsinogen into the acidic environment, allowing the conversion of pepsinogen to pepsin.

Example Question #13 : Digestive Enzymes And Cell Types

Lipase, produced by the pancreas, is responsible for breaking down which macromolecule?

Possible Answers:

Fat

Nucleic acids

Carbohydrates

Protein

Correct answer:

Fat

Explanation:

Lipase is produced by the pancreas in response to the ingestion of meals high in fat, and is responsible for cleaving fats into monoglycerides and triglycerides. Proteins are broken down by pepsin and trypsin, nucleotides are broken down primarily by high acid content, and starches and carbohydrates are broken down by amylase.

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