Lipid Digestion And Absorption

Question 1

US adult consumption of lipids

Answer 1

81 g/day

90% TAG

10% cholesterol, cholesterol esters, phospholipids, free FAs

Question 2

Sterified fat

Answer 2

Lipid

Question 3

Acid stable lipases that function in the stomach between ph 4 to ph 6

Answer 3

Acid lipase

Question 4

Secreted from glands at the back of the tongue

Answer 4

Lingual lipase

Question 5

Secreted from gastric mucosa

Answer 5

Gastric lipase

Question 6

Lipid enzymes in the stomach typically target:

Answer 6

TAGs containing short and medium FA chains

Less than 12 carbons

Ex: milk fat

Question 7

Lipid enzyme are especially important when?

Answer 7

In neonates, when milk is primary food source

Question 8

2 complementary actions of emulsification

Answer 8

Mechanical agitation and bile salt secretion

Question 9

Increases the lipid droplet surface area via peristalsis of dietary material

Answer 9

Mechanical agitation (emulsification)

Question 10

Where are bile salts made?

Answer 10

Liver

Question 11

Where are bile salts stored?

Answer 11

Gall bladder

Question 12

Where are bile salts secreted?

Answer 12

Small intestine

Question 13

Coalescing

Answer 13

Forming one mass or whole, bile salts prevent this, detergent property

Question 14

Enzymes secreted from the pancreas into the small intestine digest:

Answer 14

TAG, cholesteryl esters, and phospholipids

Question 15

Has detergent properties that stabilize particles as they become smaller, preventing them from coalescing

Answer 15

Bile salts

Question 16

The removal of specific FAs by breaking ester bonds attaching the FAs

Answer 16

Digestion in small intestine

Question 17

Why are TAGs digested in the small intestines?

Answer 17

Because the TAg is too big for intestinal mucosal cells to endocytose efficiently

Question 18

What is pancreatic lipase and what does it do?

Answer 18

It’s an esterase, and it cleaves 2 free FAs and 1 2-monoacylglycerol for a TAG

Question 19

What is colipase and what does it do?

Answer 19

Pancreatic enzyme secreted into the small in the small intestine

Function: to anchor pancreatic lipase and promote its activity when inhibitory bile salts are present

Question 20

Colipase and pancreatic lipase

Answer 20

1:1 ratio

Question 21

What digests esterified cholesterol?

Answer 21

Cholesterol esterase

Question 22

What enzymes digest phospholipids?

Answer 22

Phospholipase A2 and Lysophospolipase

Question 23

Phospholipase A2 produces:

Answer 23

A Lysophospolipid and a free FA

Question 24

Lysophospolipase produces:

Answer 24

One FA and one glycerophosphoryl base

Question 25

What happens to glycerylphosphoryl bases? And what are they formed from?

Answer 25

They can be absorbed, digested more , or excreted in feces. They're produced by Lysophospolipase

Question 26

Cholesterol esterase produces what from what?

Answer 26

Cholesterol from a cholesterol ester. It cleaves the R-C=O group and replaces it with a hydrogen.

Question 27

Gut endocrine cells sense:

Answer 27

Lipids and partially digested proteins, low pH of chyme entering the intestine

Question 28

Gut Endocrine cells are found:

Answer 28

In the mucosa layer of the lower duodenum and jejunumq

Question 29

Gut endocrine cells secrete:

Answer 29

CCK and secretin

Question 30

What is CCK?

Answer 30

Small peptide hormone secreted to the blood in response to the presence of lipids and partially digested proteins

Question 31

What does CCK promote and cause release of?

Answer 31

Pancreatic enzyme secretion, and cause gall bladder to release bile

Question 32

What does CCK decrease?

Answer 32

Gastric motility, reducing release of gastric contents to the small

Question 33

What is secretin?

Answer 33

A small peptide hormone secreted to the blood in response to the low pH of chyme entering the intestine

Question 34

What does secretin promote?

Answer 34

Release of pancreatic juice, alkaline and bicarbonate rich

Question 35

Lipid digestion in the jejunum generates what 3 products?

Answer 35

Free FA, free cholesterol, and 2-monoacylglycerol

Question 36

What are micelles and what/where are they formed?

Answer 36

Disk shaped clusters of amphipathic lipids Formed in the jejunum? From free FA, free cholesterol, 2-mono acyl glycerol, bile salts, and fat-soluble vitamins

Question 37

What are the fat soluble vitamins

Answer 37

D, E, K, A

Question 38

What are enterocytes?

Answer 38

Intestinal mucosal cells

Question 39

How are micelles arranged?

Answer 39

HydrophoBic groups are Buried. And HydropHILic groups are exposed. To the aqueous solution

Question 40

Where are micelles soluble/absorbed?

Answer 40

Soluble in the intestinal lumen, absorbed in the brush border membrane of enterocytes

Question 41

Where does complex lipid biosynthesis occur?

Answer 41

ER

Question 42

converts long chain fatty acids to their activated form by using energy from ATP -> AMP to form fatty acyl CoA

Answer 42

Thiokinase (fatty acyl-CoA synthase)

Question 43

2-monoacylglycerol is converted to TAG by adding FAs

Answer 43

TAG synthase

Question 44

Esterifies cholesterol with a FA

Answer 44

Acyl CoA-cholesterol acyltransferase

Question 45

What are chylomicron?

Answer 45

TAG and cholesterol esters surrounded by a spherical layer of phospholipids, cholesterol, and Apolipoprotein B-48 Produced at ER of enterocytes Lymph contains chylomicrons called Chyle

Question 46

What enzyme degrades TAG in the circulating chylomicrons to free FAs and glycerol?

Answer 46

Lipoprotein lipase

Question 47

Fate of free FAs?

Answer 47

Usually taken up immediately by adjacent muscle/adipose tissue. If not, will circulate with serum albumin in blood til taken up.

Question 48

What is the fate of glycerol?

Answer 48

Taken up by the liver to produce glycerol-3-phosphate which enters glycolysis or gluconeogenesis

Question 49

Remaining components of chylomicron...

Answer 49

Endocytosed in the liver

Question 50

Poor digestion and decreased absorption can lead to:

Answer 50

Increased excretion of essential dietary lipids

Question 51

Cystic Fibrosis

Answer 51

Cystic- gallbladder Fibrosis - digestion Autosomal recessive Mutations will affect Cl ion channel, affecting hydration and viscosity of mucus Thick viscous mucus blocks the secretion of pancreatic enzymes, or pancreatic insufficiency Results in delayed growth and energy deficiency Treatment includes enzyme replacements and fat-soluble vitamin supplements