Final answer:
The role of hydroxymethyl-glutaryl CoA reductase (HMG-CoAR) is to synthesize cholesterol. It is a key enzyme in the cholesterol biosynthesis pathway and is a target for statins, which reduce cholesterol levels by inhibiting this enzyme.
Step-by-step explanation:
The role of hydroxymethyl-glutaryl CoA reductase (HMG-CoAR) is A. Synthesis of cholesterol. This enzyme is key in the cholesterol biosynthesis pathway, where it catalyzes the conversion of HMG-CoA to mevalonate, which is a crucial step in the production of cholesterol. The activity of HMG-CoA reductase is regulated by feedback inhibition, where excess cholesterol and intermediates such as mevalonate suppress the enzyme's activity. Additionally, it can be inactivated by phosphorylation with hormones like glucagon and epinephrine, or activated via dephosphorylation. Statins, a class of drugs used to lower cholesterol levels in the body, function by inhibiting HMG-CoA reductase, effectively reducing the synthesis of cholesterol.