Lipid Digestion Flashcards Preview

MBOD Block 4 > Lipid Digestion > Flashcards

Flashcards in Lipid Digestion Deck (57):
1

What is a lipid?

Water insoluble biological compound soluble in fat solvents

2

What properties define whether a substance is called a lipid or not?

Solubility properties

3

Give some examples of lipids

Fatty acids, TAG, TG, cholesterol, membrane phospholipids, steroid hormones, etc.

4

Describe the structure of a fatty acid

Long chain carboxylic acid

5

What is the name for a 16C saturated FA?

Palmitic acid (ionized form = palmitate)

6

From which end does the numbering system using ω start? α?

Hydrocarbon end; Acid end

7

What is a 18C monounsaturated FA?

Oleate

8

What is the major dietary lipid?

Triacylglycerol (TAG)

9

What composes bile salts?

Cholesterol esters (planar ring structure with hydroxyl groups facing towards hydrophilic surface,
and steroidal surface facing hydrophobic areas)

10

WhatdigestsTGintomonoacylglycerolsanddiacylglycerols?

Lipase (gastric or pancreatic)

11

What protein binds to lipase and stabilizes it by displacing a bile salt in a micelle?

Colipase

12

What enzyme cleaves cholesterol esters?

Cholesterol esterase

13

What enzyme cleaves FA from TAG at the 2 position?

phospholipaseA2

14

Through what circulation are bile salts returned to the liver?

enterohepatic circulation

15

How much (percentage) of the bile salt pool is excreted?

5%

16

How is a FA activated?

Acylated by addition of CoAsh (high energy thioester) utilizing ATP to AMP, produces FA‐CoA

17

How many high energy phosphate bonds are required for FA activation in their oxidative
catabolism?

2

18

What carries FA into the lymphatic system?

Chylomicrons

19

What composes most of a chylomicron?

TAG’s

20

Are cholesterols present in chylomicrons?

Yes (hydroxyl groups pointed out)

21

If the B –apoprotein gene is going to produce a protein destined for the liver how much of the
AA transcript is produced?

100%, thus its termed ApoB‐100

22

If the B –apoprotein gene is going to produce a protein destined for the intestine how much of
the AA transcript is produced?

48%, thus ApoB‐48

23

What transfers proteins to ApoB particles?

Micosomal TG transfer protein (MTP)

24

What organelle is responsible for apo particle maturation and secetion?

Golgi

25

Where are chylomicrons synthesized?

Intestinal epithelial cell

26

Where is a TG converted to 2‐MG or FA ? (free fatty acids)

Intestional Lumen

27

Where is the TG resynthesized?

Intestinal epithelial cell

28

Where are nascent chylomicons?

Lymph

29

What forms a mature chylomicron?

ApoCII added by HDL+ApoE

30

What activates mature CM?

LPL

31

Where does the released FA travel to?

Muscles, adipose tissue, etc.

32

Where does the glycerol travel to?

Liver (glycerol cycle)

33

Does the same glycerol cleaved take part in TAG resynthesis for instance in adipocytes?

No, it’s a new glycerol molecule

34

What are some examples of lipids? (8)

1. fatty acids
2. TAGs or triglycerides
3. membrane phospholipids
4. cholesterol
5. steroid hormones
6. vitamins
7. 2nd messengers
8. PGs

35

When is a fatty acid saturated?

no double bonds within the long chain hydrocarbon

36

T/F Fatty acids are fuel molecules in metabolism

True

37

What is the major source of dietary fatty acids?

TAG

38

What gives bile acids and salts their hydrophilic and hydrophobic side to allow them to be detergents?

-OH groups are all on the same side so the side with the -OH is hydrophilic

39

Outline the steps in digestion of TAG to formation of chylomicrons

1. TG in intestinal lumen converted to 2-MG and fatty acids
2. Resynthesized into triglycerides
3. Starts to assemble into small ApoB-48 particles at RER
4. Incorporated into chylomicrons
5. Onto the golgi complex
6. Packaged for secretion for lymph
7. MTP is microsomal TG transfer protein

40

Which digestive enzyme requires protein colipase to stabilize and localize lipase near the bile salt-TG particle?

pancreatic lipase

41

What are the enzymes in order of introduction of the TG to the chylomicrons?

1. lingual lipase (short and medium TAG)
2. gastric lipase
3. pancreatic lipase (lipase, colipase, bile salts)

42

If short or medium chains of TAG are present in the digestion process, what enzymes are necessary?

only lingual lipase as this will allow it to bypass the gut and go straight to the liver

43

T/F Bile salts are recycled by entero-hepatic circulation

True, 95% saved

44

Describe the intestinal resynthesis of TG

1. activation of fatty acids
2. TAG synthesis
3. 2-MG
4. DAG
5. TAG

45

Where do chylomicrons go?

lymph

46

Where does the lipase activity to make FA occur? Where are chylomicrons made?

-gut lumen of the cell contains the lipase activity
-chylomicrons are made in mucosal cells

47

What is present outside on the structure of a lipoprotein?

cholesterol, peripheral apoprotein, amphipathic lipids

48

What is found in the interior of a lipoprotein?

choseserol ester, TAG, core of nonpolar lipids

49

What is the composition of a chylomicron in order of most to least?

TG>phospholipid>protein>cholesterol ester>cholesterol

50

What structure of the chylomicron will tell it the direction to take?

HDL + ApoE, ApoCii

51

What has the B-apoprotein gene?

VLDLs in the liver

52

If the B-apoprotein gene from the RER is sent to the liver, which gene will be present? Intestine?

Apo B-100 will be present in liver with 100% translated

Apo B-48 produced 48% of polypeptide due to RNA editing causing a stop codon

53

T/F For chylomicron synthesis to occur, an MTP is required

True, microsomal TG transfer protein

54

Where does the chylomicron go after it becomes a larger ApoB particle?

To golgi for maturation and secretion

55

Describe the path of chylomicrons wrt to the cellular components

1. brush border villae
2. SER and RER
3. Golgi
4. chylomicrons
5. lymph

56

What is the role of chylomicrons?

transport dietary TG

57

What is a water insoluble biological compound solubine in fat solvents such as alcohol, ether, chloroform which is defined by solubility properties?

lipid