Biochem

Question 1

what is the key regulatory step in steroid hormone biosynthesis?

Answer 1

STAR protein

Question 2

what does the star protein do?

Answer 2

brings cholesterol from the outer mitochondrial membrane to the inner

Question 3

what enzyme catalyzes the first step of steroid biosynthesis?

Answer 3

cholesterol desmolase

aka cholesterol side chain cleaving enzyme

Question 4

what is the difference between androgens and estrogens?

Answer 4

androgens have a ketone at C3

estrogens have a hydroxyl group at C3 and an aromatic ring

Question 5

what enzyme is needed for an androgen to be converted to an estrogen?

Answer 5

aromatase

Question 6

what is the sequence of enzymes in the steroid hormone biosynthesis pathway?

Answer 6

star protein -> cholesterol desmolase (pregnenelone) -> 3 beta hydroxysteroid dehydrogenase (progesterone) -> 17 alpha hydroxylase (17 alpha hydroxyprogesterone, androstenedione) -> aromatase (estrogens)

Question 7

which enzyme in the pathway is not a CYP enzyme?

Answer 7

3 beta hydroxysteroid dehydrogenase