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Block 3 Week 4 Meg > Valencik: Lipid transport > Flashcards

Valencik: Lipid transport Flashcards

1
Q

4 pathways of lipid transport

A

Food –> any tissue
Liver –> other tissues
Other tissues –> liver
Adipose tissue –> other tissues

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2
Q

What gets transported in lipid transport?

A 
Free fatty acids
Triglycerides
Cholesterol
Cholesterol esters
Phospholipids
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3
Q

Plasma lipid level are higher than blood (blank) and vary with dietary intake

A

glucose

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4
Q

Stored in adipose tissue, mobilize to provide energy to other tissues. Travel in the blood stream noncovalently attached to albumin.

A

free fatty acids

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5
Q

(blank) TAGs need to be used or stored. (blank) TAGs need to be used or stored.

A

dietary; synthesized

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6
Q

Storage form of cholesterol

A

cholesterol esters

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7
Q

Lipids with a hydrophilic phosphate head group

A

phospholipids

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8
Q

Macromolecular assemblies of protein and lipid aggregates

A

Lipoproteins

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9
Q

What is the protein component called in a lipoprotein?

A

apolipoprotein

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10
Q

What does the lipid component of the lipoprotein include?

A

TAGs, free fatty acids, cholesterol, cholesterol esters, phospholipids, other lipids and their derivatives

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11
Q

Two components of the lipoprotein that are amphipathic?

A

apolipoprotein and phospholipid monolayer

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12
Q

Two components of the lipoprotein that are hydrophobic?

A

cholesterol ester and triglyceride

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13
Q

When plasma lipoproteins are separated by electrophoresis, which component travels the least? What travels the furthest?

A

chylomicrons travel the least, HDL travels the most. LDL and VLDL travel in between.

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14
Q

During electrophoresis of lipoproteins, protein/lipid ratio determines how far each lipoprotein travels. If it has more lipids, it will be (blank) and travel (blank).

A

lighter; further

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15
Q

Chylomicrons and VLDLs are both very (blank). Which one is about 1micrometer in diameter? Which one is about 10-80nm in diameter?

A

hydrophobic; chylomicrons; VLDLs

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16
Q

LDLs and HDLs are much smaller in diameter than (blank)

A

chylomicrons

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17
Q

Chylomicrons have a high (blank) ratio

A

volume/surface

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18
Q

HDLs are (blank) rich and dense

A

protein

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19
Q

When fasting, where are most triglycerides found?

A

VLDLs

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20
Q

What makes up about 70% of plasma cholesterol when fasting?

A

LDL cholesterol

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21
Q

What are free fatty acids bound to?

A

albumin

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22
Q

Chylomicrons are only present when you’ve eaten a (blank) meal

A

fatty

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23
Q

(blank) contain the highest fraction of TAGs

A

chylomicrons

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24
Q

(blank) have the highest fraction of total cholesterol

A

LDLs

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25
Q

When fasting, where are the most TAGs found?

A

VLDLs

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26
Q

When fasting, where is the most cholesterol found?

A

LDL

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27
Q
  1. Fat is ingested in the diet and bile salts emulsify dietary fats in the small intestine forming mixed (blank)
A

micelles.

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28
Q
  1. Intestinal lipases degrade (blank)
A

TAGs

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29
Q
  1. Fatty acids and other breakdown products are taken up by the intestinal mucosa and converted into (blank)
A

TAGs

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30
Q
  1. TAGs are incorporated, with cholesterol and apolipoproteins, into (blank)
A

chylomicrons

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31
Q
  1. Chylomicrons move through the (blank) and bloodstream to the tissues.
A

lymphatic system

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32
Q
  1. Lipoprotein lipase, activated by (blank) in the capillary, converts TAGs to fatty acids and glycerol.
A

apoC-II

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33
Q
  1. (blank) enter cells
A

Fatty acids

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34
Q
  1. Fatty acids are (blank) as fuel or (blank) for storage
A

oxidized; reesterified

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35
Q

So, when we eat triglycerides, we start with a TAG that is digested by (blank) to produce free fatty acid and diacylglycerol. The DAG is taken to a MAG.

A

pancreatic lipase

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36
Q

Monoacylglycerol can enter the enterocyte where it can be acted on by (blank) to form new TAGs that can be repackaged to make new chylomicrons.

A

Acyl-CoA synthase

37
Q

Life span of a chylomicron

A

<1 hour

38
Q

3 Roles of apolipoproteins

A
  1. regulate plasma lipid metabolizing enzymes
  2. facilitate lipid transfer
  3. mediate endocytosis
39
Q

Chylomicrons are exocytosed into the lymphatic system and transport these two things to the rest of the body

A

“dietary” cholesterol and TAGs

40
Q

This apolipoprotein is only found on chylomicrons

A

ApoB-48

41
Q

From where do chylomicrons acquire additions apolipoproteins in the blood? What are some of these apolipoproteins?

A

From HDLs; apoC-II and apoE

42
Q

Chylomicrons want to dump their TAGs. Once they acquire apoC-II, they can bind to (blank) and hydrolyze 80-90% of TAGs. While doing this, they can also recycle some of their apos back to (blank)

A

lipoprotein lipase; HDL

43
Q

Activity of LPL is dependent on (blank)

A

apoC-II

44
Q

During TAG hydrolysis, surface phospholipids and apolipoproteins A and C peel off the surface and are transferred to HDL. This leaves behind a chylomicron (blank)

A

remnant

45
Q

Chylomicron remnants, containing primarily (blank), apoE and apoB-48, are taken up by, the liver through interaction with an apoE dependent receptor.

A

cholesterol esters

46
Q

How do lipids get transported from the liver to other tissues that need them?

A

VLDLs

47
Q

In the liver, excess carbohydrates and fats are used to synthesize (blank) and lipids

A

TAGs

48
Q

TAGs, lipids, and cholesterol are packaged into (blank)

A

VLDLs

49
Q

VLDLs are exocytosed (blank) into the blood and delivered to extra-hepatic tissues

A

directly

50
Q

The free fatty acids from TAGs are stored or used to produce energy through (blank)

A

B-oxidation

51
Q

Like chylomicrons, VLDLs quickly obtain (blank) and (blank) and additional cholesterol esters from HDLs.

A

apoCs and apoEs

52
Q

What is apo are “nascent” VLDLs born with?

A

ApoB-100

53
Q

What’s the lifespan of VLDLs?

A

< 1 hour

54
Q

What’s the difference between ApoB48 found on chylomicrons and ApoB100 found on VLDLs? What is this an example of?

A

Encoded by the same gene, but apoB-100 is much longer; tissue-specific RNA editing

55
Q

In the (blank), the RNA is post-transcriptionally altered and has a STOP codon early on to generate a shorter apo than in the liver.

A

intestine

56
Q

VLDL travels down a similar path to chylomicrons but (blank) is slower

A

hydrolysis

57
Q

Similar to chylomicrons, lipoprotein lipase frees FAs into the tissue and is coupled to the loss of apolipoproteins to (blank)

A

HDL

58
Q

These are generated as VLDLs lose their apoCs to HDL

A

IDL

59
Q

VLDLs acquire more cholesterol esters from HDLs through the activity of this protein

A

CETP

60
Q

Two types of VLDL remnants. 50% contain lots of (blank) and are endocytosed by the liver. Smaller ones become (blank) on their way to becoming LDLs.

A

apoE; IDLs

61
Q

What enzyme is attached to hepatocytes via heparin and takes IDLs to LDLs?

A

hepatic lipase

62
Q

Hepatic lipase, unlike lipoprotein lipase, is independent of (blank)

A

apoC-II

63
Q

LDLs are (blank)% cholesterol esters and (blank)% phospholipids and only carry this apolipoprotein.

A

40%; 20%; apoB-100

64
Q

Lifespan of LDLs

A

3 days

65
Q

What fraction of LDLs can bind to hepatocytes and be endocytosed? What fraction cannot?

A

2/3; 1/3

66
Q

3 things can happen if LDLs are providing excess intracellular cholesterol

A
  1. ACAT creates cholesterol esters for storage
  2. HMG-CoA reductase transcription repressed
  3. LDL receptor transcription repressed
67
Q

If LDLs are not cleared by LDL receptors, how are they cleared?

A

macrophages endocytose LDLs via scavenger receptors

68
Q

Scaveneger receptors have a higher affinity for (blank) or (blank) LDLs

A

oxidized; acetylated

69
Q

3 ways in which lipids are transferred from other tissues to the liver

A
  1. ApoE mediated endocytosis of remnant particles containing cholesterol esters
  2. CE from HDL are transferred to hepatocytes via SR-BI
  3. Large HDLs with ApoEs are endocytosed
70
Q

HDLs are released from the liver and intestine and are rich in (blank)

A

phospholipids

71
Q

HDLs do not contain these two things

A

cholesterol; cholesterol esters

72
Q

When made by the liver, HDLs have these apolipoproteins

A

apoA-I, apoA-II, apoC-I, apoC-II, apoE

73
Q

When made by the intestine, HDLs have this apolipoprotein

A

apoA-I

74
Q

HDLs are converted to (blank) and (blank)

A

HDL3 and HDL2

75
Q

HDL particles dock to the cell surface through (blank) or (blank) binding. (blank) pumps free cholesterol from the cell surface into the HDL.

A

apoA-I; apoE; ABCA1

76
Q

The cholesterol is processed in 2 steps. First, (blank) binds to the surface of the HDL and is activated by (blank) to catalyze the esterification of cholesterol.

A

LCAT; apoA1

77
Q

…Then, once a CE is formed, (blank) transfers CEs to lipoprotein remnants or LDLs

A

CETP

78
Q

So, excess cellular cholesterol is returned to the liver via lipoprotein remnants or LDLs as (blank). This occurs in an apoE dependent manner.

A

cholesterol esters

79
Q

Another way cholesterol can be delivered to hepatocytes is by HDLs remaining intact but giving off C and CEs to hepatocytes via (blank) and (blank)

A

hepatic lipase; SR-BI

80
Q

Finally, a few HDLs will acquire enough (blank) to be endocytosed themselves.

A

apoE

81
Q

What is the key way that cholesterol is transported to hepatocytes?

A

CETP dependent transfer of CEs to remnants

82
Q

Deficiency in triglyceride transfer protein. Therefore, no ApoB lipoproteins are assembled

A

ABlipoproteinemia

83
Q

Absence of ABCA1 protein. Therefore apoAs can’t acquire lipids and mature HDLs don’t form.

A

Tangier disease

84
Q

Absence of ApoClll (a LPL inhibitor).

A

Apo CIII deficiency

85
Q

Cholesterol esters cannot be transferred to other remnants.

A

CETP deficiency

86
Q

When do lipids get transferred from adipose tissue to other tissues?

A

during starvation

87
Q

4 enzymes involved in glycerolneogenesis in the liver and adipose tissue

A
  1. pyruvate carboxylase
  2. malate DH
  3. PEPCK
  4. G3PDH
88
Q

(blank) activity induced by thiazolidinediones

A

PEP Carboxykinase

89
Q

Involved in the stimulation of human fat cell lipolysis

A

ATGL lipase

Block 3 Week 4 Meg (6 decks)

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