Chapter 15 Dietary Lipid Metabolism

Question 1

Overview

1. describe lipids: traits and function

Answer 1

1. heterogenous group of water-insoluble (hydrophobic) molecules.
2. found in compartments; called droplets of TAG in adipocytes or serum/ plasma associated called lipoproteins circulating in the body
3. fat soluble vitamins, regulatory coenzyme functions
4. major source of energy for the body

Question 2

Digestion Absorption Secretion and Utilization

1. What is the components of TAG
2. what are dietary lipids primarily consist out of ?
3. where does lipid digestion begin
4. where is lipid digestion continued and completed ?

Answer 2

1. Glycerol back bone and three fatty acids attached to it; C1 is saturated C2 is not and C3 may or maybe not
2. cholesterol, cholesteryl esters, phospholipids and nonestrified (free) FA called FFA
3. in the stomach
4. in small intestine

Question 3

Lipid Digestion: STOMACH

1. What enzyme catalyzes the digestion fats ?
2. Give an example of an important role of lingual lipase ?

Answer 3

1. lingual lipase and gastric lipase. Mouth then stomach
2. lipid digestion in infants ( milk fat is primary source of calories)

Question 4

Emuslification

Emulsification

1. where does emulsification happen/occur
2. what are the two mechanisms of emulsification ?

Answer 4

1. occurs in the duodenum
2. detergent properties using bile slats and mechanical peristalsis

Emuslsification is accomplished by two complementary mechanisms, namely use of the detergent properties of the conjugated bile salts and mechanical mixing du e to peristalsis

Question 5

Degradation by Pancreatic Enzymes

1. what lipid constituents are digested in the small intestine by pancreatic enzymes ?
2. How is TAG degraded ?
3. when TAG is degraded; what are the primary products ?
4. what other enzyme binds to lipase and helps the reaction in degradation, and state where is it released ?

Answer 5

1. TAG, cholesteryl esters, and phospholipids
2. hydrolyzed by esterase and pancreatic lipase-removes- FA at C1 and C3
3. 2 MAG and a FFA
4. colipase; release from zymogen

Question 6

1. The average daily intake of lipids by U.S. is around 78 g. 90 percent and greater is made up of which constituent in that 78 grams.
2. where do digetion of dietary lipids begin ?
3. where is digestion of dietary lipids completed ?

Answer 6

1. Triglycerols
2. begins in the stomach
3. in the small intestine

Question 7

Bile salts

1. where are bile salts made ?
2. where are bile salts stored
3. Bilsalts are amphipathic derivatives of :
4. name the the constitutents of a conjugated bile salt?

Answer 7

1. in the liver
2. in the gallbladder
3. cholesterol
4. consist of hydroxylated sterol ring and a side chain to which ( GLYCINE or TAURINE) is covalently attached by an AMIDE linkage

The emulsifying agents interact with the dietary lipid droplets and the aqueous duodenal contents, therby stabilizing the droplets as they become SMALLER from PERISTALSIS. trait ( PREVENTION OF COALESCING)

Question 8

Control of Pancreatic Secretion

1. Enzymes coming from the pancrease plays a role in degradation of lipids in the small intestine. What basic control system regulates this process ?
2. In response to the presence of lipids in the duodenum and the jujenum, their cell mucosa produces a peptide hormone. What is this peptide hormone
3. CCK acts on which orgran
4. How does CCK act on the gallbladder
5. what hormone decreases gastric “motility” -resulting in a slower relase of gastric contents released in the small intestine

Answer 8

1. It is hormonally controlled
2. CCK cholecystokinin
3. gallbladder
4. CCK acts on the gallbladder causing it contract and release bile, a mixture of bile salts, phospholipids and free cholesterol
5. cholecystokinin

Question 9

Secretin

1. A peptide hormone released as well from intestinal cells and causes the pancreas to release BICARBONATE ?
2. what is the role of bicarbonate in digestion
3. Secretin is released in response to

Answer 9

1. Secretin
2. neutralize the pH of intestinal contents
3. low pH of chyme entering the intestine from the stomach

Overall:
CCK: contraction of pancreas: slows motility
Secretin: responds to low pH of chyme entering the intestine from the stomach (High in bicarb)

Question 10

Resyntheis of Triacylglycerol and cholesteryl esters

1. Long chain FA are first converted into their activated form. What is this form called ?
2. what enzyme converts a long chain FA to its active form ( Fatty acyl coa) ?
3. which lengths of fatty acids do not require to be incorporated in the chylomicron and instead directly enter into the blood.
4. which length of fatty acids are NOT converted to their CoA derivatives and are not reestrified to 2 MAG ?

The “mixture” of lipids absorbed by the enterocytes migrates to the smooth endoplasmic reticulum (SER) where biosyntheis of complex lipids takes place

Answer 10

1. Fatty Acyl Coa
2. THIOKINASE (fatty acyl coenzyme A (CoA ) synthetase
3. short and medium chain length fatty acids
4. short and medium chain length fatty acids

Question 11

Chylomicrons

1. what is a chylomicron
2. what is found in a chylomicron
3. what is the role of a chylomicron

Answer 11

1. A droplet of fat in blood or lymph AFTER absorption from the small intestine
2. consists of ultra small parts of phospholipids cholesterol and triglycerides
3. Fat transport (to various parts of the body)