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Medical Biochemistry > Ch. 18: Lipids III: Plasma Lipoproteins > Flashcards

Ch. 18: Lipids III: Plasma Lipoproteins Flashcards

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USMLE® Step 1 flashcards
1
Q

Apoliproteins: ApoA-I

Associated lipoprotein?
Function/characteristics?

A

HDL

Activates lecithin:cholesterol acyltransferase (LCAT)

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2
Q

Apoliproteins: ApoB-48

Associated lipoprotein?
Function/characteristics?

A

Chylomicrons

Derived from apoB-100 gene via RNA editing in intestinal epithelium
Lacks LDL receptor-binding domain of apoB-100

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3
Q

Apoliproteins: ApoB-100

Associated lipoprotein?
Function/characteristics?

A

VLDL, IDL, LDL

Binds to LDL receptor

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4
Q

Apoliproteins: ApoC-I

Associated lipoprotein?
Function/characteristics?

A

Chylomicrons, VLDL, IDL, HDL

May also activate lecithin:cholesterol acyltransferase (LCAT)

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5
Q

Apoliproteins: ApoC-II

Associated lipoprotein?
Function/characteristics?

A

Chylomicrons, VLDL, IDL, HDL

Activates lipoprotein lipase (LPL)

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6
Q

Apoliproteins: ApoC-III

Associated lipoprotein?
Function/characteristics?

A

Chylomicrons, VLDL, IDL, HDL

inhibits lipoprotein lipase (LPL)

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7
Q

Apoliproteins: ApoD

Associated lipoprotein?
Function/characteristics?

A

HDL

Associated with lecithin:cholesterol acyltransferase (LCAT)

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8
Q

Apoliproteins: ApoE

Associated lipoprotein?
Function/characteristics?

A

Chylomicron remnants, VLDL, IDL, HDL

Binds to LDL receptor

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9
Q

Lipoprotein lipase (LPL):

What time of enzyme is this?
In what tissues is it concentrated?
What is its function?

A

Serine esterase

Muscle & adipose tissue

Main enzyme in processing chylomicrons & VLDL (via hydrolysis of FAs from TAGs)

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10
Q

Hepatic lipase:

What are its functions?
What does it respond positively to? Negatively to?

A

Continues lipolysis of VLDL & IDL ➡️ LDL
Hydrolyzes PLs and HDL-TAGs

➕: androgens
➖: ⬆️ estrogen

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11
Q

Lecithin:cholesterol acyltransferase (LCAT):

What does it circulate with?
What is its function?

A

HDL, LDL, ApoD, Cholesteryl ester transfer protein (CETP)

Transfers LCFAs from PLs to cholesterol ➡️ forms cholesterol esters (for storage & transport in lipoprotein core)

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12
Q

Acyl-CoA:cholesterol acyltransferase (ACAT):

Location?
What is its function?

A

Intracellular enzyme

Esterifies free cholesterol via linking to an FA ➡️ for storage in liver parenchymal cells

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13
Q

What is the forward cholesterol transport pathway?

A

Transport cholesterol from liver ➡️ peripheral cells & tissues

(via VLDL ➡️ IDL ➡️ LDL)

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14
Q

What is the reverse cholesterol transport pathway?

A

Transport of cholesterol from extrahepatic tissues ➡️ liver, for excretion in bile

(via HDL)

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15
Q

Hyperlipoproteinemia: phenotype I

Lipoprotein in excess?

A

Chylomicrons

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16
Q

Hyperlipoproteinemia: phenotype IIa

Lipoprotein in excess?

A

LDL

17
Q

Hyperlipoproteinemia: phenotype IIb

Lipoprotein in excess?

A

LDL

VLDL

18
Q

Hyperlipoproteinemia: phenotype III

Lipoprotein in excess?

A

Beta-VLDL

19
Q

Hyperlipoproteinemia: phenotype IV

Lipoprotein in excess?

A

VLDL

20
Q

Hyperlipoproteinemia: phenotype V

Lipoprotein in excess?

A

Chylomicrons

VLDL

21
Q

Lipid-lowering drugs: Cholestyramine & colestipol

Characteristics/Function?

A

Non-absorbable resins

Interrupt enterohepatic circulation of bile acids

22
Q

Lipid-lowering drugs: Nicotinic acid

Characteristics/Function?

A

➖ hepatic secretion of VLDL, suppresses mobilization of FAs ➡️ ⬇️ VLDL & LDL

23
Q

Lipid-lowering drugs: Clofibrate, gemfibrozil

Characteristics/Function?

A

➕ LPL ➡️ rapid turnover of VLDL

Gemfibrozil: ➖ VLDL secretion

24
Q

Lipid-lowering drugs: Probucol

Characteristics/Function?

A

Blocks intestinal cholesterol transport ➡️ ⬇️ plasma cholesterol (no effect on TAG)

⬇️ HDL cholesterol levels

25
Q

Lipid-lowering drugs: Statins

Characteristics/Function?

A

➖ regulatory step of cholesterol biosynthesis

➖ hepatic cholesterol synthesis, upregulates LDL receptor activity ➡️ ⬇️ serum cholesterol & LDL cholesterol

Medical Biochemistry (23 decks)

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