Cholesterol & Steroids (Module 3 Lecture 4)

Question 1

Describe the structure of cholesterol.

Answer 1

Tetracyclic ring structure attached to a long hydrocarbon chain and a polar OH on the C3.

Question 2

Why are cholesterol esters important?

Answer 2

1. CE’s are more hydrophobic than cholesterol.

2. CE’s are how cholesterol is transported between cells in lipoproteins and stored intracellularly as lipid droplets.

Question 3

What two enzymes are involved in CE formation?

Answer 3

1. ACAT: Intracellular enzyme which transfers fatty acid from acyl-CoA.
2. LCAT: Extracellular enzyme which transfers fatty acid from lecithin (phosphatidylcholine).