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Flashcards in lipid digestion Deck (42):
1

Composition of lipids in the human diet
90%: ?
10%: ?

90%: TAG
10%: Phospholipids, Cholesterol, FFA

2

For the following location, list what enzymes for lipid digestion can be found there:
mouth

lingual lipase

3

For the following location, list what enzymes for lipid digestion can be found there:
stomach

lingual lipase and gastric lipase

4

For the following location, list what enzymes for lipid digestion can be found there:
Small intestine

pancreatic enzymes and bile salts

5

In regards to lipid digestion, where does absorption occur?

jejunum

6

All 3 ligases have the same activity. What is this?

Remove FAs from positions 1 and 3 - leaving 2 FFA and one 2-monoacylglycerol

7

Lingual lipase is secreted by cells at the back of the tongue and has a pH optimum. Why is its activity slow?

because the enzyme is only active at the surface of the lipid droplet

8

Gastric lipase is secreted by the gastric mucosa. It has a pH optimum. Like lingual lipase, it is limited by the surface of the lipid droplet. How is its activity increased?

peristaltic movement

9

The FFA produced ruing the reaction of lipids with gastric lipase act as ____

detergents

10

Gastric digestion may account for up to ___% of total TAG hydrolysis

30

11

The pancreas secretes ____ and ____

lipase; procolipase

12

Procolipase (secreted by pancreas) is converted to colipase by ____

trypsin

13

Lipase alone is inhibited by ____ ____

bile salts

14

How is inhibition of lipase by bile salts prevented?

Colipase binds lipase to mixed micelles

15

What are the major products of pancreatic lipase?

FFA and 2-monoacylglycerol

16

___% of the TAG may be hydrolyzed to glycerol

20

17

Phospholipase A2 is secreted as a zymogen (prophospholipase A2). It is activated by what? What else is required for this reaction?

trypsin; bile salts

18

Describe the action of Phospholipase A2

removes one FA molecule from the 2 position of phospholipids to yield one FFA and one lysophospholipid

19

Bile salts are produced in the ____ and derived from ____

liver; cholesterol

20

Bile salts are secreted into and stored where?

gall bladder

21

What are the 3 components of bile and what do they form?

bile salts, phospholipid, and cholesterol - form micelles

22

True or false? Fat soluble vitamins are not included in the micelles

False; they are included

23

What do mixed micelles allow?

the distribution of the products of lipid digestion to the intestinal epithelium for absorption

24

Do short and medium chain FAs need help from bile salts to enter the intestinal epithelial cells for absorption?

no

25

Absorption of cholesterol into the intestinal epithelium is poorly understood. What is the most important carrier protein that is known?

NPC1L1

26

Intestinal epithelial cells contain ABC transporter proteins which pump sterols out of the cell. What would the effect be on cholesterol absorption, if plant sterols were consumed?

decrease in cholesterol absorption by:
-competing with cholesterol

27

Virtually all FFA and MAG are absorbed but only ___-___% of dietary cholesterol is absorbed

30-40%

28

Bile salts are absorbed essentially completely in the ____

ileum

clinical note: can be used to lower cholesterol

29

Absorbed lipids are repackaged as ____ by the intestinal epithelial cells

chylomicrons

30

Where in the cell are FAs transported to in order to become TAGs?

ER

31

In TAG synthesis, the FFAs are first converted to FA-CoAs by what enzyme?

acyl-CoA synthase

32

The remainder of the TAGs are synthesized by what pathway?

phophatidic acid pathway

33

Short and medium chain FAs enter the hepatic portal vein as FFA. They are transported to the ___ by binding to ___

liver; albumin

34

The major apo-portein added to form chylomicrons is called ___-___

B-48

35

Apo-proteins are synthesized where in the cell? Apo-proteins join newly formed lipids (creating chylomicrons) where in the cell?

rough ER; golgi

36

The major function of chylomicrons is what?

get TAGs in the blood stream

37

This disorder of lipid digestion is caused by anything that interrupts lipid digestion/absorption. Symptoms are presence of excess fat in stool and greasy and foul-smelling stools.

Steatorrhea

38

If a patient's stool contains large amounts of FAs and is clay colored, what is the likely diagnosis?

Insufficient bile (biliary obstruction)
digestion proceeds but absorption is compromised due to lack of bile salts; this also gives the stool a clay color

39

If a patient's stool contains large amounts of TAG and there is a decreased absorption of fat and fat soluble vitamins, what is the likely diagnosis?

insufficient pancreatic enzymes (cystic fibrosis, pancreatitis)

40

This drug is an inhibitor of gastric and pancreatic lipase. It reduces fat absorption by preventing TAG digestion. Side effect may be similar to steatorrhea

Orlistat

41

This drug causes FAs to become resistant to lipase, but fat soluble vitamins may be passed through with the drug itself.

Olestra

42

This drug inhibits NPC1L1 and diminishes cholesterol absorption

Ezetimibe