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MBOD Block 4 > Lipid Digestion > Flashcards

Lipid Digestion Flashcards

1
Q

What is a lipid?

A

Water insoluble biological compound soluble in fat solvents

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2
Q

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

A

Solubility properties

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3
Q

Give some examples of lipids

A

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

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4
Q

Describe the structure of a fatty acid

A

Long chain carboxylic acid

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5
Q

What is the name for a 16C saturated FA?

A

Palmitic acid (ionized form = palmitate)

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6
Q

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

A

Hydrocarbon end; Acid end

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7
Q

What is a 18C monounsaturated FA?

A

Oleate

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8
Q

What is the major dietary lipid?

A

Triacylglycerol (TAG)

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9
Q

What composes bile salts?

A 
Cholesterol esters (planar ring structure with hydroxyl groups facing towards hydrophilic surface,
and steroidal surface facing hydrophobic areas)
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10
Q

WhatdigestsTGintomonoacylglycerolsanddiacylglycerols?

A

Lipase (gastric or pancreatic)

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11
Q

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

A

Colipase

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12
Q

What enzyme cleaves cholesterol esters?

A

Cholesterol esterase

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13
Q

What enzyme cleaves FA from TAG at the 2 position?

A

phospholipaseA2

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14
Q

Through what circulation are bile salts returned to the liver?

A

enterohepatic circulation

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15
Q

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

A

5%

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16
Q

How is a FA activated?

A

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

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17
Q

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

A

2

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18
Q

What carries FA into the lymphatic system?

A

Chylomicrons

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19
Q

What composes most of a chylomicron?

A

TAG’s

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20
Q

Are cholesterols present in chylomicrons?

A

Yes (hydroxyl groups pointed out)

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21
Q

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

A

100%, thus its termed ApoB‐100

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22
Q

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

A

48%, thus ApoB‐48

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23
Q

What transfers proteins to ApoB particles?

A

Micosomal TG transfer protein (MTP)

24
Q

What organelle is responsible for apo particle maturation and secetion?

A

Golgi

25
Q

Where are chylomicrons synthesized?

A

Intestinal epithelial cell

26
Q

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

A

Intestional Lumen

27
Q

Where is the TG resynthesized?

A

Intestinal epithelial cell

28
Q

Where are nascent chylomicons?

A

Lymph

29
Q

What forms a mature chylomicron?

A

ApoCII added by HDL+ApoE

30
Q

What activates mature CM?

A

LPL

31
Q

Where does the released FA travel to?

A

Muscles, adipose tissue, etc.

32
Q

Where does the glycerol travel to?

A

Liver (glycerol cycle)

33
Q

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

A

No, it’s a new glycerol molecule

34
Q

What are some examples of lipids? (8)

A
  1. fatty acids
  2. TAGs or triglycerides
  3. membrane phospholipids
  4. cholesterol
  5. steroid hormones
  6. vitamins
  7. 2nd messengers
  8. PGs
35
Q

When is a fatty acid saturated?

A

no double bonds within the long chain hydrocarbon

36
Q

T/F Fatty acids are fuel molecules in metabolism

A

True

37
Q

What is the major source of dietary fatty acids?

A

TAG

38
Q

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

A

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

39
Q

Outline the steps in digestion of TAG to formation of chylomicrons

A
  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
Q

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

A

pancreatic lipase

41
Q

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

A
  1. lingual lipase (short and medium TAG)
  2. gastric lipase
  3. pancreatic lipase (lipase, colipase, bile salts)
42
Q

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

A

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

43
Q

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

A

True, 95% saved

44
Q

Describe the intestinal resynthesis of TG

A
  1. activation of fatty acids
  2. TAG synthesis
  3. 2-MG
  4. DAG
  5. TAG
45
Q

Where do chylomicrons go?

A

lymph

46
Q

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

A
  • gut lumen of the cell contains the lipase activity

- chylomicrons are made in mucosal cells

47
Q

What is present outside on the structure of a lipoprotein?

A

cholesterol, peripheral apoprotein, amphipathic lipids

48
Q

What is found in the interior of a lipoprotein?

A

choseserol ester, TAG, core of nonpolar lipids

49
Q

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

A

TG>phospholipid>protein>cholesterol ester>cholesterol

50
Q

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

A

HDL + ApoE, ApoCii

51
Q

What has the B-apoprotein gene?

A

VLDLs in the liver

52
Q

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

A

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
Q

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

A

True, microsomal TG transfer protein

54
Q

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

A

To golgi for maturation and secretion

55
Q

Describe the path of chylomicrons wrt to the cellular components

A
  1. brush border villae
  2. SER and RER
  3. Golgi
  4. chylomicrons
  5. lymph
56
Q

What is the role of chylomicrons?

A

transport dietary TG

57
Q

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

A

lipid

MBOD Block 4 (15 decks)

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