Cholesterol and Cholesterol Esters Review Flashcards Preview

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Flashcards in Cholesterol and Cholesterol Esters Review Deck (12)

What is mevalonate?

Mevalonate is an important intermediate in cholesterol biosynthesis.


What reaction generates mevalonate?

The reaction generated by HMG-CoA reductase.


Why do we care about HMG-CoA reductase?

The reaction catalyzed by HMG-CoA reductase is the limiting enzyme in cholesterol biosynthesis


What drug targets HMG-CoA reductase?



What electron carrier is necessary for the synthesis of cholesterol?

NADPH! It is oxidized to NADP+ in the conversion of HMG-CoA to mevalonate


What is an important regulator of HMG-CoA reductase?

Cholesterol- the end product of cholesterol synthesis negatively feeds back to inhibit HMG-CoA reductase activity.


What enzyme is responsible for the conversion of cholesterol into a cholesterol ester?

ACAT: Acyl-CoA cholesterol acyl-transferase


What is the purpose of cholesterol esters?

Cholesterol esters make storage of cholesterols in LDLs and VLDLs etc more efficient.

Cholesterol esters = storage


What is the enzyme responsible for regulating the conversion of cholesterol to bile acids?

7-alpha hydroxylase


How does increased cholesterol affect HMG-CoA reductase?

HMG-CoA reductase is inhibited.

Remember: cholesterol negatively feedsback onto HMG-CoA reductase to inhibit it's activity (no cholesterol synthesis is needed)


How does high levels of cholesterol affect the activity of ACAT and 7-alpha-hydroxylase?

They are both activated. ACAT is responsible for the esterification of cholesterol for storage, and 7-alpha-hydroxylase is responsible for the production of bile acids (high cholesterol indicates food intake --> bile salts are needed for digestion)


Where in the cell is HMG-CoA synthase?

Only in the mitochondria.

HMG-CoA synthase