AP Biology : Understanding Emulsification

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #34 : Digestive System

A patient is admitted to the hospital with severe abdominal pain. A scan reveals that the gall bladder has multiple stones in it, and one is blocking the cystic duct.

Which of the following molecules would be inadequately absorbed during gall bladder obstruction?

Possible Answers:

Fatty acids

Monosaccharides

All molecule types will be inadequately absorbed

Amino acids

Correct answer:

Fatty acids

Explanation:

The gall bladder is important because of its storage and release of bile during digestion. Bile is important in the emulsification (or breaking up) of nonpolar fats in the aqueous small intestinal fluid. Cystic duct obstruction would result in bile being unable to reach the small intestine, and triglycerides would be unable to be properly emulsified and absorbed.

Example Question #35 : Digestive System

Where is bile stored when digestion is not occurring?

Possible Answers:

Adrenal glands

Kidney

Spleen

Appendix

Gall bladder

Correct answer:

Gall bladder

Explanation:

The liver produces bile, which travels down the bile duct to be released into the small intestine, specifically the duodenum. When the duct is not open, bile backs up and gets stored in the gall bladder. Once the duct is open, when the small intestine senses the presence of food, the gall bladder will release the bile to emulsify fats during digestion.

Example Question #36 : Digestive System

Which of the following does NOT play a role in the emulsification of dietary lipids?

Possible Answers:

Phospholipids

Bile salts

Lipase

Small intestine motility

Correct answer:

Lipase

Explanation:

Both bile salts and phospholipids are excreted from the bile duct into the upper small intestine (duodenum) to emulsify lipids. They are both amphipathic molecules, which means they have non-polar/lipophilic ends that can bind to lipids and polar/hydrophilic ends that can bind to water, thus emulsifying the lipids that they contact.

As these compounds are excreted from a single duct, small intestine motility allows them to mix with the contents of the small intestine and emulsify more lipids than they would be able to in a still environment. Small intestine motility also helps to break up large globules of dietary fat.

Once emulsified, dietary fat can be broken down by lipase, but lipase itself does not enhance emulsification.

Example Question #37 : Digestive System

Which organ stores the compound responsible for emulsifying lipids during digestion?

Possible Answers:

Small intestine

Pancreas

Gall bladder

Liver

Correct answer:

Gall bladder

Explanation:

Fats are generally composed of nonpolar lipids, making them hydrophobic and insoluble. In order to digest fats, they must be grouped together to increase their surface area and allow for enzyme interaction, digestion, and absorption.

Fat emulsification is the process of increasing the surface area of fats in the small intestine by grouping them into small clusters. This is the responsibility of bile, a liquid created by the liver and stored in the gallbladder. Actual digestion of the fats is then accomplished by lipase, an enzyme from the pancreas. Digested lipids are then transported into the lacteals of the microvilli for transportation through the lymphatic system before entering the blood.

Example Question #15 : Digestive Physiology

Bile is produced in the __________, stored in the __________, and released into the __________.

Possible Answers:

liver . . . gallbladder . . . small intestine

liver . . . gallbladder . . . large intestine

kidneys . . . gallbladder . . . small intestine

gallbladder . . . gallbladder . . . small intestine

Correct answer:

liver . . . gallbladder . . . small intestine

Explanation:

The liver is responsible for synthesizing bile salts; these salts are transferred into the gallbladder as bile. The gallbladder stores bile, which it then secretes into the small intestine. Bile contributes to digestion by breaking up large fat globules, a process known as emulsification. Fats are insoluble in water, so emulsification provides pancreatic lipase with more surface area on which to act. 

Neither the spleen nor the large intestine are relevant answers to this sentence. The large intestine helps remove undigested waste from the body, absorbs water from waste, and produces/absorbs vitamins (due to colonies of beneficial bacteria that live in the large intestine). The spleen is an organ responsible for filtering the blood and housing white blood cells; it is not involved in digestion.

Example Question #38 : Digestive System

Bile salts are amphipathic and essential for fat absorption. Which of the following nutrients will be difficult to absorb in a patient with an inability to secrete bile salts into the stomach?

I. Vitamin A

II. Vitamin B

III. Vitamin C

Possible Answers:

I and III

I only

II only

I and II

All of these

Correct answer:

I only

Explanation:

Bile salt emulsifies fat into chylomicrons to allow for absorption. Of the choices, only vitamin A is fat-soluble. Vitamins B and C are both water-soluble.

Example Question #39 : Digestive System

Bile salts emulsify dietary fats by breaking them down into smaller clusters and creating a molecule called a __________.

Possible Answers:

cluster

micelle

chylomicron

bolus

globule 

Correct answer:

micelle

Explanation:

Bile salts surround fat droplets in order to create micelles. These micelles are more accessible to the enzymes that have the ability to break them down further. Chylomicrons are lipoproteins that are important in transport and metabolism of lipids.

Example Question #1 : Understanding Emulsification

Bile salts make fat droplets more accessible to the enzyme __________.

Possible Answers:

lingual lipase

pancreatic lipase

trypsin

pepsin

chymotrypsin

Correct answer:

pancreatic lipase

Explanation:

Once large fat clusters are broken down by bile salts to become smaller micelles, pancreatic lipase has more surface area to access fats. The enzymes are able to reach the fat droplet through the gaps between bile salts. Fats are not emulsified by bile yet in the mouth, so lingual lipase acts upstream of bile to hydrolize long chain hydrocarbons. The other answer choices are proteases. 

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