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Flashcards in Steroid Biosynthesis Deck (59)
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1

5 steroid hormone classes

Progestins
Glucocorticoids
Mineralocorticoids
Estrogens
Androgens

2

Progesterone is an example of the ______ hormone class.

Where is it synthesized, distributed, and what does it mediate?

Progestins

Synthesized in adrenal glands, ovaries, testes

Distributed to uterus

Mediates implantation and maintenance of pregnancy

3

Cortisol, cortisone, and corticosterone are examples of what class of hormone?

Where are they synthesized, distributed, and what do they mediate?

Glucocorticoids

Synthesized in adrenal glands

Distributed to many tissues/organs; increases BP and Na uptake in kidneys; mediates response to stress by increasing protein catabolism and gluconeogenesis and reducing inflammation

4

Aldosterone and 11-deoxycorticosterone are members of what hormone class?

Where are they synthesized, distributed, and what do they mediate?

Mineralocorticoids

Synthesized in adrenal glands

Distributed to kidney tubules, colon, parotid gland

Increases Na/H2O retention, K excretion, and BP

5

Estradiol and estrone are members of ______ hormone class

Where are they synthesized and distributed, and what do they mediate?

Estrogens

Synthesized in ovaries, placenta, adipose tissue

Distributed to primary and secondary reproductive organs

Mediate feminization, estrous cycle, inhibit testosterone synthesis

6

Testosterone, 5-alpha-dihydrotestosterone, and DHEA are members of what hormone class?

Where are they synthesized and distributed and what do they mediate?

Androgens

Synthesized in adrenal glands, ovaries, and testes

Distributed to primary and secondary reproductive organs and muscle

Mediate spermatogenesis, secondary male characteristics, bone maturation, and virilization

7

Cholesterol fate in liver

Used to synthesize bile acids

8

Cholesterol fate in adrenal glands, ovaries, and testes

Synthesize steroid hormones

9

Cholesterol fate in skin

Used to synthesize vit D

10

What are the main lipophilic ligands?

Steroid hormones

Fat-soluble vitamins = ADEK

11

Are growth factors hydrophilic or lipophilic ligands?

Hydrophilic

12

Precursor/starting material to cholesterol synthesis

Sterane ring

13

What are some examples of cholesterol-based lipophilic signaling molecules/ligands?

Cortisol
Estradiol
Thyroxine
Testosterone
Vitamin D3
Retinoic acid (makes Vit A)

14

T/F: most signaling molecules are hydrophobic and readily diffuse across the membrane

False, most are hydrophilic and require cell surface receptors

15

Would you classify steroid signaling as fast or slow responses?

Slow - because most of them initiate or repress gene expression which takes time

16

Steroid hormones are synthesized from cholesterol in the smooth ER of the adrenal cortex, ovaries, and testes

Where do these tissues obtain cholesterol?

Circulating LDL

De novo synthesis from acetyl CoA

Cholesterol esters stored in cytoplasmic lipid droplets

17

Which of the following requires the most 5-carbon IPP units to synthesize?

A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin K
E. Vitamin B

B. Vitamin D


Requires 6 IPP units, while vit A, E, and K require 4. Vitamin B is water soluble

18

The synthesis of steroid hormones begins with the RATE-LIMITING step catalyzed by ________, an enzyme that incorporates a carbonyl group on the D ring of cholesterol and cleaves off a 6-carbon piece of its side chain to form ____________

Desmolase

Pregnenolone

19

The rate limiting step of steroid hormone synthesis (the conversion of cholesterol to pregnenolone via RL enzyme desmolase) MUST be regulated. What is an important positive regulator of desmolase?

ACTH

20

Pregnenolone is an alcohol that acts as a modulator of NT signaling in the brain without being converted to other steroids. It affects the NMDA glutamate receptor involved in memory and learning.

Pregnenolone must be converted to _______ for synthesis of other proestrogens, this is done with enzymes _______ and __________

Progesterone

17-alpha-hydroxylase

3-beta-hydroxysteroid dehydrogenase

21

Once pregnenolone is converted to progesterone via 17-alpha-hydroxylase and 3-beta-hydroxysteroid dehydrogenase, what are the possible end products of steroid hormone synthesis?

17-alpha hydroxylase is involved in multiple arms of the steroid hormone synthesis pathway, so possible outcomes include:

Mineralocorticoids
Glucocorticoids
Estrogens
Androgens

22

What is unique about glucocorticoids as they relate to mineralocorticoids, and how do they compare to mineralocorticoids in terms of concentration?

Glucocorticoids have affinity for mineralocorticoid receptors and are 100 times more concentrated than mineralocorticoids

23

Which of the following is progesterone specifically converted to in a tissue specific manner?

A. Aldosterone in the adrenal cortex
B. Cortisol in the adrenal cortex
C. Estradiol from testosterone precursor in the ovaries
D. Testosterone and dihydrotestosterone in testes
E. All of the above

E. All of the above

24

Which of the following is most essential to formation of aldosterone or cortisol (i.e., not the enzyme important in other common pathways)

A. 21-alpha-hydroxylase
B. 17,20-lyase
C. 17-beta-hydroxysteroid dehydrogenase
D. Aromatase
E. 5-alpha reductase

A. 21-alpha-hydroxylase

25

Which of the following is most essential to the formation of androgens and estrogens (i.e., not the enzyme common to other hormone pathways)?

A. 21-alpha-hydroxylase
B. 17,20-lyase
C. 17-beta-hydroxysteroid dehydrogenase
D. Aromatase
E. 5-alpha reductase

B. 17,20 lyase

26

T/F: Desmolase is only found in tissues that produce steroid hormones, such as gonads and adrenal cortex

True

27

What specific type of hormone stimulates expression and activity of desmolase?

Peptide hormones

28

What are 3 examples of peptide hormones that stimulate the action of desmolase, where are they located, and what activates them?

ACTH - secreted from pituitary gland in stressful conditions; activated by corticotropin-releasing hormone (CRH) from hypothalamus

LH - secreted from pituitary gland; activated by gonadotropin-releasing hormone (GnRH) from hypothalamus

FSH - secreted from pituitary gland; activated by GnRH from hypothalamus

29

FSH in females affects menstruation, and stimulates estradiol production by activating the enzyme _____

Aromatase

30

A relatively common inherited defect is a deficiency in 21-hydroxylase enzyme. What does this lead to?

Hyponatremia and hypotension d/t decreased production of aldosterone

Hypoglycemia d/t decreased production of cortisol

Causes virilism in females