MCAT Biology : Other Digestive Physiology

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

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Example Question #1 : Other Digestive Physiology

Calcium (Ca2+) levels are least directly involved in which of the following process?

Possible Answers:

Bone formation

Muscle contraction

Biotin and vitamin K production

Signal transduction

Correct answer:

Biotin and vitamin K production

Explanation:

Calcium plays an important role in many physiological functions, including signal transduction, muscle contraction, and bone formation. Of all of the processes listed in the answer choices, calcium is least directly related to biotin and vitamin K production. Biotin and vitamin K are synthesized by gut flora.  

Example Question #133 : Excretory And Digestive Systems

How could increasing the amount of fiber in one's diet reduce the occurrence of constipation?

Possible Answers:

Increase the volume of water entering the gut

Decrease the volume of water entering the gut

Increase absorption of other nutrients by gastrointestinal enterocytes

Increase absorption of fiber by gastrointestinal enterocytes

Correct answer:

Increase the volume of water entering the gut

Explanation:

This question asks us to understand osmolarity and osmosis. Osmosis is the property of water whereby it moves from a high concentration of water to a low concentration of water, while osmolarity refers to the tendency of solutes to affect the draw of water from one area to another. In more practical terms, this means that water moves from areas of low solute concentration to areas of high solute concentration. Fiber is not digestible by humans, thus it cannot be absorbed by the gastrointestinal enterocytes. Additionally, because fiber cannot be absorbed, it cannot affect the absorption of other compounds in the gut to a great extent. Fiber does, however, increase the number of solute particles in the gut, and so draws water from the circulation and tissues via osmosis. Increasing the flow of water into the lumen will add more water to stool and help relieve constipation.

Example Question #3 : Other Digestive Physiology

The vitamins include A, B, C, D, E, and K. Which vitamins are fat-soluble and which are water-soluble?

Possible Answers:

Vitamins A, D, E, and K are fat-soluble. Vitamins B and C are water-soluble.

Vitamins B and C are fat-soluble. Vitamins A, D, E, and K are water-soluble.

Vitamin C is the only water-soluble vitamin. The rest are fat-soluble.

All of the vitamins are fat-soluble. 

Correct answer:

Vitamins A, D, E, and K are fat-soluble. Vitamins B and C are water-soluble.

Explanation:

Fat-soluble vitamins include A, D, E, and K. Water-soluble vitamins include B and C. 

Example Question #2 : Other Digestive Physiology

Which of the following nutrients enters the lymphatic vessels (lacteals) of the villi upon absorption?

Possible Answers:

Disaccharides

Amino acids

Triglycerides

Nucleotide monomers

Monosaccharides

Correct answer:

Triglycerides

Explanation:

While carbohydrates and proteins are digested and absorbed directly into the bloodstream, dietary fats are packaged into chylomicrons and moved into the lacteal. The lymphatic system then transports the dietary fats to the large veins of the body via the thoracic duct. The majority of fats are absorbed by this process, but a smaller minority of shorter fatty acids are able to float freely into the bloodstream.

Example Question #3 : Other Digestive Physiology

What is the main site of water-soluble vitamin absorption?

Possible Answers:

Duodenum

Jejunum

Ileum

Large intestine

Correct answer:

Large intestine

Explanation:

The majority of food absorption occurs in the later two-thirds of the small intestine, the jejunum and the ileum. Water and water-soluble vitamins, however, are absorbed in the large intestine.

Example Question #4 : Other Digestive Physiology

In the human body, the colon primarily absorbs __________.

Possible Answers:

only salts

only water

water and salts

only nutrients

Correct answer:

water and salts

Explanation:

The colon extracts water and salts while forming feces. The colon also absorbs some nutrients that made it through the small intestine without being absorbed, but its main job is water and salt absorbtion. 

Example Question #5 : Other Digestive Physiology

What is the primary purpose of the colon?

Possible Answers:

Reabsorb salt and water

Absorb proteins and vitamins

Secrete water

Absorb fatty acids

Correct answer:

Reabsorb salt and water

Explanation:

The primary purpose of the colon is to reabsorb water and salt (NaCl) in order to dehydrate the stool into a compact form for defecation. On average, the colon reabsorbs 1.5L of water per day and moves excreted sodium from the stool back into systemic circulation for further use. Inhibition of sodium reabsorption by the cholera toxin is what leads to severe dehydration and diarrhea seen in the disease.

Example Question #6 : Other Digestive Physiology

A specific bacterium causes diarrhea in patients. Knowing this, which section of the digestive system would be most affected by the bacterium?

Possible Answers:

Large intestine

Small intestine

Liver

Stomach

Correct answer:

Large intestine

Explanation:

The primary roles of the large intestine are water and electrolyte absorption. If this role is impeded by a pathogen, diarrhea results. Dehydration can also be a secondary effect of large intestine damage, and can lead to death.

The small intestine is primarily involved in nutrient absorption and chemical digestion. The stomach is involved in mechanical digestion, and some chemical digestion. The liver produces bile, which can be secreted to emulsify fats.

Example Question #9 : Other Digestive Physiology

Which part of the large intestine rests along the posterior abdominal wall?

Possible Answers:

Transverse colon

Descending colon

Sigmoidal colon

Ascending colon

Rectum

Correct answer:

Transverse colon

Explanation:

The posterior abdominal wall is the location of many organs, one of which is the transverse colon. This part of the colon brings waste from one side of the body to the other, and hangs along the posterior wall in the abdominal cavity.

The colon consists of a few main parts. The ascending colon is the first region of the large intestine, connecting it to the small intestine. The ascending colon transitions into the transverse colon, which then becomes the descending colon. The descending colon transitions into the muscular sigmoidal colon, which terminates in the rectum.

Example Question #7 : Other Digestive Physiology

Which part of the colon moves digested food in the vertical direction?

Possible Answers:

Sigmoidal colon

Transverse colon

Appendigial colon

Descending colon

Ascending colon

Correct answer:

Ascending colon

Explanation:

The colon consists of a few main parts, including the ascending colon. The ascending colon is the first region of the large intestine, connecting it to the small intestine. The ascending colon transitions into the transverse colon, which then becomes the descending colon. The descending colon transitions into the muscular sigmoidal colon, which terminates in the rectum.

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