Cholesterol Metabolism Flashcards
What are four functions of cholesterol?
membranes
bile acids
steroid hormones
vitamin D
What is the one precursor of Cholesterol and where does it come from?
Acetyl CoA and it comes from: pyruvate dehydrogenase,
b-oxidation of fatty acids, and oxidation of ketogenic amino acids (e.g. leucine, lysine)
Cholesterol synthesis happens in the nucleus and doesn’t require much energy. (T/F)
False, It happens in the cytosol and requires a lot of energy, that’s why the “on/off switch” is early in the synthesis pathway.
HMG CoA Reductase is controlled by..
transcription
degradation
phosphorylation
inhibited by statins
When there is high cholesterol, SCAP is inactive, but when there is low cholesterol SCAP does this.
SCAP cleaves the DNA binding domain of SREBP, which then translocates to the nucleus and regulates transcription of HMG CoA reductase.
High levels of what promote proteolysis of HMG CoA reductase?
Sterols
In the fasted state, HMG-CoA is phosphorylated and inactive (T/F)
T
Where is the main source for cholesterol synthesis? How can cholesterol be exported from there?
The Liver. Cholesterol can be exported as cholesterol esters (VLDL) or bile acids.
What inhibits bile acid production?
Bile acids inhibit the 7alpha-hydroxylase.
The majority of bile salts are recycled back to the liver, while a small portion is excreted in the feces. (T/F)
T
When bile salts act as detergents, they do what specifically to dietary fats?
Make dietary fats soluble and accessible to lipase.
Nascent chylomicrons are composed of what and where are they initially sent?
They are made of dietary fat and cholesterol in intestinal epithelial cells. They are first sent to the lymph.
Mature chylomicrons are made after what is combined with nascent chylomicrons?
HDL particles transfer ApoCII to nascent chylomicrons to make mature chylomicrons. ApoCII activates lipoprotein lipase (LPL).
What does nascent VLDL from the liver require to become mature?
Other than an education on proper manners, it needs ApoCII and ApoE from circulating high density lipoprotein (HDL) to become mature.
Familial hypercholesterolemia are formed from mutations in what?
The LPL receptor. Symptoms are: hyperlipidemia, premature CVD, and xanthomas
