AP Biology : Understanding Other Digestive Physiology

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #21 : Digestive Physiology

Which of the following enzymes does NOT directly contribute to protein digestion?

Possible Answers:

Gastrin

Chymotrypsin

Trypsin

Pepsin

Correct answer:

Gastrin

Explanation:

Gastrin is secreted in the stomach, and stimulates the secretion of hydrochloric acid by parietal cells. The other three enzymes directly aid in the digestion of proteins. Trypsin and chymotrypsin are released from the pancreas into the duodenum, and pepsin digests proteins located in the stomach. Each of these has different cleavange targets within protein sequences and can be used as a restriction enzyme in experimental procedures.

Example Question #22 : Digestive Physiology

Which of the following functions is NOT accomplished by the liver?

Possible Answers:

Blood filtration

Vitamin storage

Glycogen storage

Antibody creation

Correct answer:

Antibody creation

Explanation:

The liver is a very important organ with many interrelated functions, however, the liver is not responsible for the creation of antibodies. This is done by plasma cells, a key cell type in the immune system.

Example Question #23 : Digestive Physiology

Which of the following statements about the hormone secretin is false?

Possible Answers:

It stimulates bicarbonate secretion in the pancreas

All of these choices are correct

It inhibits motility in the stomach

It is released when acid enters the duodenum, where it is secreted

Correct answer:

All of these choices are correct

Explanation:

Secretin is a hormone released by the duodenum in response to an influx of acid. The hormone targets the stomach, to reduce the amount of acid that can pass through to the small intestine, and the pancreas, to increase secretion of bicarbonate, which neutralizes the acidity.

Example Question #24 : Digestive Physiology

Which of the following statements about cholecystokinin (CCK) and gastrin is true?

Possible Answers:

Both hormones target the stomach, but for different functions

Both hormones are secreted only by the duodenum

Both hormones target the pancreas, but for different functions

Both hormones target the gall bladder to release bile

Correct answer:

Both hormones target the stomach, but for different functions

Explanation:

Cholecystokini (CCK) targets the stomach to inhibit motility, while gastrin targets the stomach to increase motility. Gastrin is secreted by the duodenum and the stomach, but targets only the stomach. CCK, however, targets the stomach, pancreas, and gall bladder.

Example Question #25 : Digestive Physiology

Which enzyme operates at the lowest pH?

Possible Answers:

Carboxypeptidase

Pepsin

Amylase

Trypsin

Lipase

Correct answer:

Pepsin

Explanation:

Pepsin is the only enzyme out of the given choices that functions in the stomach, where the pH is very low (acidic). Trypsin, carboxypeptidase, and lipase all function within the small intestine, where the pH is usually more basic to neutralize the pH of chyme as food is digested. Amylase is found in saliva and functions in the mouth, where pH is about neutral.

Example Question #26 : Digestive Physiology

One of the functions of the liver is __________.

Possible Answers:

to produce bile, triglycerides, and cholesterol

to produce insulin in its specialized beta cells

to physically digest food

to act as the main storage center for bile

to secrete epinephrine and norepinephrine

Correct answer:

to produce bile, triglycerides, and cholesterol

Explanation:

The liver has a large number of functions, including metabolizing toxins, synthesizing proteins, and storing glucose in the form of glycogen. The only answer choice that describes liver functions is the production of bile, triglycerides, and cholesterol.

The pancreas produces insulin from beta cells, the gall bladder stores bile, and the adrenal medulla secretes epinephrine and norepinephrine. Physical digestion takes place mainly in the mouth and stomach, not the liver.

Example Question #1 : Understanding Other Digestive Physiology

Which of the following statements about the pancreas is incorrect?

Possible Answers:

The pancreas is the body's main site of glycogen storage

The pancreas secretes hydrolytic enzymes through the pancreatic duct and into the small intestine

The pancreas secretes the hormones insulin and glucagon

The pancreas secretes bicarbonate to neutralize chyme

Correct answer:

The pancreas is the body's main site of glycogen storage

Explanation:

Glycogen is stored primarily in cells of the liver and muscles. The pancreas is responsible for secreting hydrolytic enzymes into the small intestine via the pancreatic duct. Along with these digestive enzymes the pancreas releases bicarbonate, which reacts in an acid-base reaction with acidic stomach chyme to pervent it from damaging the intestine. The pancreas also releases insulin and glucagon, among other hormones.

Example Question #28 : Digestive Physiology

What macromolecule is digested first by chemical means?

Possible Answers:

Nucleic acids

Carbohydrates

Fats

Proteins

Correct answer:

Carbohydrates

Explanation:

Carbohydrates begin their digestion in the mouth, where salivary amylase is produced.

Fats are emulsified by bile and digested by lipase in the small intestine. Nucleic acids are also digested in the small intestine by nucleases. Proteins begin their digestion in the stomach, where the low pH of gastric juice begins the breakdown process and pepsin begins to cleave peptide bonds. Protein digestion continues in the small intestine with other protease enzymes.

Example Question #29 : Digestive Physiology

Which of the following is a true statement with regard to digestive enzymes?

Possible Answers:

Proteases only exist in the mouth

Amylase breaks down amino acids

Proteases only exist in the small intestine

Most water absorption is performed in the stomach

Lipases digest fats

Correct answer:

Lipases digest fats

Explanation:

Amylase breaks down starch in the mouth and small intestine. Proteases are found in the stomach and small intestine. Water absorption occurs in the intestines (mostly the large intestine). Lipases break down lipids; fats are a type of lipid.

Example Question #2 : Understanding Other Digestive Physiology

Ammonia is a byproduct of digestive absorption. It is converted to urea by the liver and expelled in the urine.

Which macromolecule is responsible for the presence of the ammonia byproduct during digestion and absorption?

Possible Answers:

Fatty acids

Proteins

All macromolecules create an ammonia byproduct

Carbohydrates

Correct answer:

Proteins

Explanation:

In order to answer this question, visualize the macromolecules as their monomers. The chemical formula for ammonia is , so the monomer will need to include nitrogen. Carbohydrates are chains of monosaccharides and are only composed of carbon, hydrogen, and oxygen. Fatty acids are nonpolar molecules, and are composed of only carbon and hydrogen. Proteins are composed of amino acid monomers. Amino acids have an amino terminus, which includes a nitrogen atom. As a result, only proteins have the nitrogen atom which can be used in the byproduct of ammonia.

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