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IUSM Biochemistry > Cholesterol > Flashcards

Cholesterol Flashcards

1
Q

How much can diet change cholesterol levels?

A

10 - 15%

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2
Q

What do statins do?

A

Lower cholesterol by inhibiting HMG-CoA reductase

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3
Q

All 27 carbons in cholesterol are derived from ________

A

acetyl CoA

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4
Q

Cholesterol is a very hydrophobic molecule that has 27 carbons. On what carbon is the only hydrophilic OH group located?

A

3

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5
Q

How many rings does cholesterol have?

A

4

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6
Q

What are the two types of HMG CoA synthase? What pathways are they used in?

A

Mitochondrial - keytone bodies

Cytoplasmic - cholesterol

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7
Q

What is the major electron carrier for cholesterol synthesis?

A

NADPH

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8
Q

What is the rate limiting step of cholesterol synthesis catalyzed by? What type of energy input does it require?

A

HMG-CoA Reductase
Acetyl CoA -> Mevalonate
NADPH

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9
Q

What are two potential side effects of statins?

A

myopathy and rhabdomyolysis

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10
Q

What is a way to store cholesterol?

A

Cholesteryl Esters

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11
Q

High levels of cholesterol cause _________ of HMG-CoA reductase

A

proteolysis

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12
Q

What transcription factors control the transcription of HMG-CoA reductase?

A

Sterol regulatory element-binding proteins (SREBP)

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13
Q

Is HMG-CoA reductase activated by dephosphorylation or phosphorylation?

A

dephosphorylation

stimulated by insulin

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14
Q

What are the major sites of cholesterol synthesis?

A

Liver

Intestine

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15
Q

Bile acids are synthesized in ________ and sent to ________ for storage

A

liver

gall bladder

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16
Q

What is the rate limiting step of bile acid synthesis?

A

Cholesterol 7alpha-hydroxylase (CYP7A1) places OH on C7 of cholesterol

17
Q

What are the major components of bile?

A

Bile salts, water, cholesterol, bilirubin

18
Q

How do you convert bile acids to biles salts?

A

Create an amide bond by adding glycine or taurine

19
Q

What inhibits 7alpha-hydroxylase? in bile salt synthesis

A

bile salts

20
Q

80% of US gallstones are ________ stones

A

cholesterol

21
Q

VLDLs are produced primarily as a result of what process?

A

Made from carbohydrates as a result of breaking down glucose into acetyl-CoA

22
Q

Chylomicrons are made by the liver primarily with what?

A

Dietary triglycerides

23
Q

Why is the protein B-48 shorter than B-100?

A

Because there is a premature stop codon when it is being synthesized in the intestine.

24
Q

What is the name of the enzyme that converts cholesterol to cholesteryl ester by esterifying HDL cholesterol so it is retained in particles?

A

Lecithin Cholesterol Acyltransferase (LCAT)

25
Q

What enzyme transports cholesterol esters and TGs between lipoproteins?

A

cholesterol ester transfer protein (CETP)

26
Q

What is the major function of chylomicrons?

A

Transport dietary triglycerides

27
Q

What is the major function of VLDLs?

A

Transport endogenous triglycerides mainly from excess carbs

28
Q

What is the major function of LDLs?

A

Transport cholesterol to tissues

29
Q

What does a deficiecy in LDL receptors cause?

A

High blood cholesterol

30
Q

What scavenger receptor binds to HDL?

A

SR-B1

31
Q

What scavenger receptors are located on macrophages and bind oxidized LDL (superoxide)?

A

SR-A1 and SR-A2

32
Q

What are foam cells?

A

macrophages engorged with lipid

33
Q

cholesterol ester transfer protein (CETP) transfers cholesterol from _____ to ______

A

HDL to VLDL

34
Q

Inhibiting CETP raises what levels?

A

HDL

35
Q

What is the biggest health concern for people with familial hypercholesterolemia (FH)?

A

Heart Disease

36
Q

What is defective in a person with familial hypersholesterolemia (FH)?

A

Defective LDL receptor

Can’t take in LDLs so they stay in the bloodstream

37
Q

What is defective in Tangier Disease?

A

ABC A1

38
Q

What does ABC A1 do?

A

Transports cholesterol out of macrophages into HDL

39
Q

What happens to a person with Tangier Disease?

A

Extremely low levels of HDL, cholesterol accumulates in macrophages

IUSM Biochemistry (11 decks)

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