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M1 Biochemistry > Exam 1- Plasma Lipoproteins > Flashcards

Exam 1- Plasma Lipoproteins Flashcards

1
Q

Function of plasma lipo-proteins

A

Transport hydrophobic materials in aqueous solution (plasma)

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2
Q

List lipoprotein subclasses in order of size, density, and lipid content

A

Increasing size, decreasing density, and decreasing lipid content:
HDL —> LDL —> IDL —> VLDL —> Chylomicrons

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3
Q

Function of Chylomicron, HDL, LDL & VLDL

A

Chylomicron: Gut —> tissues (transfers dietary fat)
HDL: tissues —> liver (gut) (collect fat from peripheral tissues)
LDL & VLDL: Liver —> tissues

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4
Q

Difference between free and esterified cholesterol

A

Esterified cholesterol: fa added to cholesterol which is the most hydrophobic molecule known

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5
Q

Apoproteins definition

A

Apoproteins associated with the lipoprotein coat, mediates the interactions of lipoproteins with cells (& each other)

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6
Q

Amino acid residues associated with hydrophilic and lipophilic component of apoproteins

A

Lipophilic: methionine, leucine, alanine, valine

Hydrophilic: aspartate, threonine, arginine, histidine

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7
Q

Define inside and outside of a lipoprotein

A

Core- Cholesterol ester

Coat-
phospholipid and unesterified cholesterol

Wrapped around it- apolipoprotein

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8
Q

Lipoprotein lipase (LPL) - Function & location

A

In adipose tissue & striated muscle

Interacts with chylomicrons and VLDL via apo C-II

To release 3 free fatty acids & glycerol

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9
Q

Hepatic Lipase- Function & Location

A

Function: liver, and also plasma & macrophages

Function: TAG —> 2-monoacylglycerol + 2 free fatty acids

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10
Q

Hepatic Lipase- secondary function and health implication

A

Also acts to bind lipoprotein particles, mediating their interactions with receptors such as the LDL R and SRB1

Influence atherosclerotic plaque formation

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11
Q

Lecithin: Cholesterol Acyl transferase (LCAT)

A

In HDL: made in liver, activated by apoA1

Lecithin (phosphatidylcholine) + Cholesterol —> Lysolecithin + Cholesterol ester

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12
Q

Cholesteryl ester transfer protein (CETP)

A

Bound to HDL

Transfer cholesterol esters from HDL —> LDL & VLDL
- allows you to move cholesteryl esters with having to de-esterify and re-esterify

Transfer TAG’s from LDL & VLDL —> HDL

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13
Q

Inhibition of CETP raises

A

HDL cholesterol and may be used to treat cardiovascular disease

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14
Q

ABCA1 transporter- Function & Location

A

Location: macrophages, brain, liver, adrenal, etc

Function: mediates transport of cholesterol, phospholipids, and other metabolites from cells —> HDL

ACBA1 is essential for & represents RLS of HDL

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15
Q

Apolipoprotein associated with HDL

A

ApoA-I, apoA-II, and apo-E

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16
Q

Describe characteristics of HDL (4)

A
  • synthesized in the liver as an apoA-I, apoA-II, and apo-E containing particle
  • upon release from the liver into the blood, acquires cholesterol from peripheral tissues via ABC’s or C-II from plasma
  • its unesterified cholesterol is esterified by LCAT
  • HDL also acts as a reservoir for apo C-II and E donating them to VLDL & chylomicrons as they are encountered in circulation
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17
Q

As HDL acquires more cholesterol esters, it is transformed from ______ to ______. And then interacts with _______ on the __________ that facilitates __________________________________.

A

HDL3 —> HDL2
SRB1 (scavenger receptor type B1), liver
The removal of the cholesterol esters and returns the HDL to the circulation

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18
Q

Note another way that HDL can be internalized

A

ApoE is recognized by the LDL R and so HDL may also be internalized via that route

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19
Q

_____ is sometimes called “good cholesterol” because _________

A

HDL

It removes cholesterol from peripheral tissues and is associated with lowered risk of atherosclerosis

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20
Q

Antiatherogenic effects of HDL are dependent on

A

Concentration and quality

21
Q

Role of HDL

A

Redistribution of lipids from cells with excess cholesterol (ex. Macrophages) to cells requiring cholesterol or to the liver for excretion

22
Q

HDL precursors (_______) synthesized in ____ are mostly _____ or derived from surface material from _______

A

Pre-beta HDL

Liver and intestine

Apo-A1

Chylomicrons

23
Q

Reverse cholesterol transport

A

Pre-beta HDL, HDL3, and HDL2 can accept cholesterol from peripheral tissues back to the liver

24
Q

ApoE allows HDL2 particles to expand by

A

Enrichment with CE of the core after LCAT converts free cholesterol to cholesterol ester

25
Q

Larger HDL (_______ or ________) with ApoE can deliver cholesterol to the liver via the _______

A

HDL1 or HDL2

LDL R

26
Q

Significance of HDL with ApoM

A

Higher quality HDL in terms of anti-atherosclerotic properties.
It contains sphingosine-1-phosphate involved in reverse transport

27
Q

HDL types in order of increasing size

A

Pre-beta HDL (apoA-1) —> HDL 3 —> HDL 2 —> HDL 1

HDL 2 & 1 have ApoE and can therefore bind LDL R’s on liver

28
Q

ABCA1 in other tissues (not liver or intestine) functions to

A

Add further cholesterol resulting in a discoid also HDL that is rich in free cholesterol

29
Q

LCAT acts to

A

Esterify free cholesterol to cholesterol esters which result in a spherical HDL

30
Q

Phospholipids transfer protein (PLTP) acts to

A

Liberate phospholipids from other lipoprotein classes to add to HDL

31
Q

Apolipoproteins in chylomicrons

A

Apo-B-48 and C-II

32
Q

Chylomicrons carry _____ from _____

A 
Dietary fat (TAG’s and cholesterol) 
Gut
33
Q

Chylomicrons are synthesized in

Delivered via

A

Intestinal mucosa

Delivered via the thoracic duct into the venous circulation

34
Q

In capillaries of muscle and adipose, LPL recognizes ______ and removes _____

A

ApoCII (on chylomicrons)

TAG’s

35
Q

Remnant chylomicrons depleted of ____, are taken up by the ____ and are incorporated into _____

A

TAG’s and apoCII
Liver
VLDL

36
Q

Exogenous & Endogenous pathway

A

Dietary fat packaged into chylomicrons
Capillaries remove free fatty acids (TAG’s)
Leaves smaller and more dense lipoprotein which is taken up into the liver
Repackaged and released as VLDL from liver (endogenous)

37
Q

Fat that ends up as VLDL is both

A

Fat not used up by body from chylomicrons and fat synthesized in the liver

38
Q

VLDL apolipoproteins

A

B-100, C-II, E

39
Q

Apolipoproteins associated with IDL

A

B-100, C-II, E

40
Q

Apolipoproteins associated with LDL

A

B-100

41
Q

VLDL is synthesized in the _____
Contains _______
As travels in the blood, it loses ________ to _______ via the action of ________
And its cholesterol population is progressively more esterified by _______

A 
Liver
TAG’s, cholesterol, apoB-100, C-II, and E 
TAG’s and apo C-II 
Adipose and muscle 
LPL
LCAT
42
Q

LDL contains _______ and is very rich in _______

A

ApoB100 and some ApoE

Cholesterol esters

43
Q

Peripheral tissues that have LDLR on their surfaces can bind _____ via its _____.

A

LDL
ApoB100 and apoE
LDL is disassembled and its cholesterol is used by tissues

44
Q

The family of lipoproteins that carries TAG’s and cholesterol to the peripheral tissues from the liver

A

VLDL, IDL, LDL

45
Q

Describe synthesis and release of apolipoprotein B

A

Synthesized in the RER
Incorporated into particles with TAG, cholesterol, and phospholipids in the SER
After the addition of carbohydrate residues in G, they are released from the cell by reverse pinocytosis
Chylomicrons pass into lymphatic system
VLDL secreted into space of Disse and then into hepatic sinusoids through fenestrae in the endothelial lining

46
Q

Lipoprotein a

A

Variant of lDL with associated apo(a)

Independent risk factor for atherosclerosis and consequent heart attack and stroke

47
Q

Sequence of lipoprotein (a) similar to

A

Plasminogen (dissolves fibrin clots)

Significance might be in its ability to interfere with fibrinolysis

48
Q

LDL receptor - state 5 components

A

Binding, internalization, and disassembly of LDL
Regulated by cellular cholesterol
Determines LDL level in blood
Defective in familial hypercholesterolemia
Induced by Statin drugs

M1 Biochemistry (17 decks)

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