Cholestrol Biosynthesis Flashcards
Assertion: HMGR is regulated by both phosphorylation and gene expression.
Reason: Cellular cholesterol levels influence both HMGR activity and transcription.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: AMP-activated protein kinase (AMPK) inhibits HMGR activity.
Reason: AMPK phosphorylates HMGR, reducing its enzymatic function.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: Insulin stimulates cholesterol biosynthesis.
Reason: Insulin activates phosphatases that dephosphorylate and activate HMGR.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: Elevated intracellular cholesterol decreases HMGR synthesis.
Reason: High sterol levels inhibit HMGR gene transcription.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: LDL receptors play a role in plasma cholesterol regulation.
Reason: LDL receptor-mediated endocytosis removes cholesterol from circulation.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: Cholesterol biosynthesis begins with the synthesis of mevalonate.
Reason: Mevalonate is synthesized from HMG-CoA by HMG-CoA reductase.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: HMG-CoA reductase is a key enzyme in cholesterol biosynthesis.
Reason: It catalyzes the conversion of HMG-CoA to acetyl-CoA.
C. Assertion is true, but the reason is false.
Correct Answer: C
Assertion: Fatty acid synthase complex contains multiple enzyme activities.
Reason: The complex is responsible for the de novo synthesis of fatty acids.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: Mevalonate is a precursor in cholesterol synthesis.
Reason: Mevalonate is formed via reduction of HMG-CoA.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: Cholesterol is utilized in bile acid synthesis.
Reason: Bile acids are formed from cholesterol in the liver.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: Cholesterol promotes degradation of HMGR.
Reason: Cholesterol induces polyubiquitination of HMGR, targeting it for proteasomal degradation.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: HMGR is embedded in the endoplasmic reticulum membrane.
Reason: Its sterol-sensing domain detects changes in intracellular cholesterol levels.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: Statin drugs lower intracellular cholesterol levels.
Reason: Statins inhibit HMGR, reducing mevalonate and cholesterol synthesis.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: The flux through the mevalonate pathway influences HMGR degradation.
Reason: High pathway flux increases HMGR degradation via proteolysis.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
Assertion: Glucagon suppresses cholesterol biosynthesis.
Reason: It increases phosphorylation of HMGR through AMPK activation.
A. Both assertion and reason are true, and the reason is the correct explanation.
Correct Answer: A
