Steroidogenesis and Metabolism

Question 1

any of various compounds containing a 17-carbon 4-ring system and including the sterols and the numerous hormones and glycosides

Answer 1

Steroid

Question 2

lipid structure consisting of 4 linked hydrocarbon rings forming the bulky steroid structure and a hydrocarbon tail linked to one end of the steroid and a hydroxyl group linked to the other end.

Answer 2

Cholesterol

Question 3

Steroidogenesis can occur in what organs

Answer 3

Adrenal cortex, testes, ovaries, ovarian corpus luteum, and the placenta

Question 4

This protein is essential for the transport of cholesterol to P450scc in the inner mitochondrial membrane

Answer 4

StAR – Steroidogenic acute regulatory protein

Question 5

All mammalian steroid hormones a re formed from cholesterol via ______ thru a series of reactions

Answer 5

Pregnenolone

Question 6

What are the steroids made in zona glomerulosa

Answer 6

Mineralocorticoids (principal product is aldosterone)

Question 7

What are the steroids made in zona fasciculata

Answer 7

Glucocorticoids esp cortisol

Question 8

What are the steroids made in zona reticularis

Answer 8

Androgens – dehydroepiandrosterone

Question 9

Major regulator of salt balance

Answer 9

Aldosterone

Question 10

Shape of the right adrenal gland

Answer 10

Pyramidal

Question 11

Shape of the left adrenal gland

Answer 11

Cresentic

Question 12

Enzymes involved in steroidogenesis are found either in _____ or _____

Answer 12

Mitochondria or in the cytoplasmic reticulum

Question 13

This is a smooth ER enzyme that acts upon either progesterone or more commonly pregnenolone

Answer 13

17 a-hydroxylase

Question 14

Most potent natural glucocorticoid hormone in humans

Answer 14

Cortisol

Question 15

11B hydroxylase is a _____ enzyme

Answer 15

Mitochondrial

Question 16

Synthesis of aldosterone follows the mineralocorticoid pathway and occurs in the

Answer 16

Zona glomerulosa

Question 17

Pregnenolone is converted to progesterone by the action of what enzymes?

Answer 17

3a-hydroxysteroid dehydrogenase (3a-OHSD) and δ5,4-isomerase.

Question 18

How does K ions exert a stimulatory effect on aldosterone secretion?

Answer 18

K ions cause depolarization of the z. glomerulosa cells, allowing Ca ions to enter. The increase in intracellular Ca fuels the Ca dependent intracellular events triggered by angiotensin II

Question 19

Main extracellular stimuli which regulate aldosterone secretion

Answer 19

Ang II, K+, and ACTH

Question 20

The major androgen or androgen precursor produced by the adrenal cortex is

Answer 20

Dehydroepandrosterone (DHEA)

Question 21

Most potent adrenal androgen

Answer 21

Testosterone

Question 22

Reduction of adrostenedione at the C17 position results in the formation of

Answer 22

Testosterone

Question 23

What is the adrenogenital syndrome

Answer 23

Adrenal androgen production increases markedly if glucocorticoid biosynthesis is impeded by the lack of one of the hydroxylases

Question 24

2 pathways where testosterone is metabolized

Answer 24

Oxidation at the 17 position

Reduction of the A ring double bond and the 3 ketone

Question 25

Among the 2 pathways where testosterone is metabolized, which is the more efficient one?

Answer 25

The oxidation at the 17 position

Question 26

Most significant metabolic product of testosterone

Answer 26

DHT

Question 27

Dihydrotestosterone is formed from testosterone through action of which enzyme

Answer 27

5a reductase

Question 28

90% of testosterone produced is ozidized into

Answer 28

17 ketosteroids

Question 29

Testicular androgens are synthesized in the interstitial tissue by the

Answer 29

Leydig cells

Question 30

The immediate precursor of the gonadal steroids, as for the adrenal steroids,

Answer 30

Cholesterol

Question 31

The conversion of cholesterol to pregnenolone in the ovary and the testis is promoted by

Answer 31

LH

Question 32

The rate limiting step in testicular steroidogenesis is

Answer 32

Delivery of cholesterol to the inner membrane of the mitochondria by StAR

Question 33

Pregnenolone can also be converted to testosterone by what pathway

Answer 33

Dehydroepiandrosterone or | Δ5 pathway

Question 34

T or F conversion of estrogens occurs mainly in the adrenal cortex

Answer 34

F: it is more in the peripheral tissues and ovaries

Question 35

Primary estrogen of ovarian origin

Answer 35

17B estradiol

Question 36

Estriol is produced from the

Answer 36

Placenta

Question 37

This is formed if the substrate of the aromatase enzyme complex is testosterone

Answer 37

Estradiol

Question 38

These are the source of androstenedione and testosterone

Answer 38

Theca cells

Question 39

Only steroid that is not bound to protein

Answer 39

Aldosterone

Question 40

Major site of cortisol metabolism

Answer 40

Liver

Question 41

Estrone and estradiol and their metabolites undergo which reactions

Answer 41

Sulfation by sulfotransferases and | Glucoronidation by glucoronyltransferases

Question 42

The catecholamines are synthesized from tyrosine in the

Answer 42

Chromafin cells of the adrenal medulla

Question 43

Major product of the adrenal medulla is

Answer 43

Epinephrine

Question 44

The conversion of tyrosine to epinephrine requires four sequential steps

Answer 44

Ring hydroxylation Decarboxylation Side chain hydroxylation to form norepi N-methylation to form epi

Question 45

Immediate precursor of catecholamines

Answer 45

Tyrosine

Question 46

Rate limiting enxyme in catecholamine biosynthesis

Answer 46

Tyrosine hydroxlase

Question 47

T or F catecholamines can cross the BBB that’s why there’s enough supply to the brain from the systemic circulation

Answer 47

F: catecholamines can’t cross the BBB that’s why they must be synthesized locally

Question 48

Precursor of dopamine that can cross the BBB

Answer 48

L-dopa

Question 49

DBH uses ____ as electron donor; ____ at the active site and _____ as modulator

Answer 49

Ascorbate- electron donor Copper at active site Fumarate – modulator

Question 50

Conversion of norepi to epi occurs in the

Answer 50

Cytoplasm

Question 51

PNMT catalyzes the N-methylation of norepinephrine to form epinephrine in the

Answer 51

Epinephrine forming cells of the adrenal medulla