Cholesterol Flashcards
How much can diet change cholesterol levels?
10 - 15%
What do statins do?
Lower cholesterol by inhibiting HMG-CoA reductase
All 27 carbons in cholesterol are derived from ________
acetyl CoA
Cholesterol is a very hydrophobic molecule that has 27 carbons. On what carbon is the only hydrophilic OH group located?
3
How many rings does cholesterol have?
4
What are the two types of HMG CoA synthase? What pathways are they used in?
Mitochondrial - keytone bodies
Cytoplasmic - cholesterol
What is the major electron carrier for cholesterol synthesis?
NADPH
What is the rate limiting step of cholesterol synthesis catalyzed by? What type of energy input does it require?
HMG-CoA Reductase
Acetyl CoA -> Mevalonate
NADPH
What are two potential side effects of statins?
myopathy and rhabdomyolysis
What is a way to store cholesterol?
Cholesteryl Esters
High levels of cholesterol cause _________ of HMG-CoA reductase
proteolysis
What transcription factors control the transcription of HMG-CoA reductase?
Sterol regulatory element-binding proteins (SREBP)
Is HMG-CoA reductase activated by dephosphorylation or phosphorylation?
dephosphorylation
stimulated by insulin
What are the major sites of cholesterol synthesis?
Liver
Intestine
Bile acids are synthesized in ________ and sent to ________ for storage
liver
gall bladder
What is the rate limiting step of bile acid synthesis?
Cholesterol 7alpha-hydroxylase (CYP7A1) places OH on C7 of cholesterol
What are the major components of bile?
Bile salts, water, cholesterol, bilirubin
How do you convert bile acids to biles salts?
Create an amide bond by adding glycine or taurine
What inhibits 7alpha-hydroxylase? in bile salt synthesis
bile salts
80% of US gallstones are ________ stones
cholesterol
VLDLs are produced primarily as a result of what process?
Made from carbohydrates as a result of breaking down glucose into acetyl-CoA
Chylomicrons are made by the liver primarily with what?
Dietary triglycerides
Why is the protein B-48 shorter than B-100?
Because there is a premature stop codon when it is being synthesized in the intestine.
What is the name of the enzyme that converts cholesterol to cholesteryl ester by esterifying HDL cholesterol so it is retained in particles?
Lecithin Cholesterol Acyltransferase (LCAT)
What enzyme transports cholesterol esters and TGs between lipoproteins?
cholesterol ester transfer protein (CETP)
What is the major function of chylomicrons?
Transport dietary triglycerides
What is the major function of VLDLs?
Transport endogenous triglycerides mainly from excess carbs
What is the major function of LDLs?
Transport cholesterol to tissues
What does a deficiecy in LDL receptors cause?
High blood cholesterol
What scavenger receptor binds to HDL?
SR-B1
What scavenger receptors are located on macrophages and bind oxidized LDL (superoxide)?
SR-A1 and SR-A2
What are foam cells?
macrophages engorged with lipid
cholesterol ester transfer protein (CETP) transfers cholesterol from _____ to ______
HDL to VLDL
Inhibiting CETP raises what levels?
HDL
What is the biggest health concern for people with familial hypercholesterolemia (FH)?
Heart Disease
What is defective in a person with familial hypersholesterolemia (FH)?
Defective LDL receptor
Can’t take in LDLs so they stay in the bloodstream
What is defective in Tangier Disease?
ABC A1
What does ABC A1 do?
Transports cholesterol out of macrophages into HDL
What happens to a person with Tangier Disease?
Extremely low levels of HDL, cholesterol accumulates in macrophages
