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Biochem II > Exam 2 Steroid Hormones > Flashcards

Exam 2 Steroid Hormones Flashcards

1
Q

Agents that are produced in endocrine tissues and exert their effectiveness on other tissue types

A

Hormones

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2
Q

Hormones interact with ______ that results in changes of gene expression

A

Receptors

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3
Q

When a hormone exerts effects on the same cell

A

Autocrine

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4
Q

When a hormone exerts effects on adjacent cells

A

Paracrine

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5
Q

Hormone binding is affected by which two factors?

A
  1. Hormone concentration

2. Receptor activity/concentration

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6
Q

Factors that affect hormone concentration (5)

A
  1. *** The rate of synthesis and secretion of hormones
  2. Proximity of the target cell to the hormone (dilution effect)
  3. Dissociation constant (Kd) of the hormone with the plasma transport protein
  4. Conversion of hormone from inactive to active forms
  5. Rate of clearance from plasma by digestion, metabolism, or excretion
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7
Q

Factors that affect cell response to hormones (5)

A
  1. *** Number, activity, and state of occupancy of cell receptors
  2. Metabolism of the hormone in the cell
  3. Presence of other factors required for cell response
  4. Up- or downregulation of the receptor due to binding ligand
  5. Downregulation of a receptor
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8
Q

Hormones are present in very (low / high) concentrations?

A

Low

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9
Q

Two characteristics of receptors involved with hormone binding

A
  1. Have to be very discriminating to target ligand

2. Must bind saturation kinetics

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10
Q

Receptors have at least _______ domains?

A

Two

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11
Q

The binding of a single hormone to a receptor and coupling to intracellular signaling

A

Receptor-effector coupling

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12
Q

Group of hormones that undergo facilitative diffusion and bind to intracellular receptors

A

Group 1 - lipophilic

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13
Q

Group of hormones that bind on the surface of the membrane and initiate intracellular signal cascades

A

Group 2 - hydrophilic

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14
Q

Gene transcription is regulated almost exclusively by which group of hormones?

A

Group 1 - lipophilic

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15
Q

What hormone is the adrenal gland stimulated by, and what is the result?

A

Adrenal gland is stimulated by adrenalcorticotropic hormone (ACTH) that causes the expression of an esterase that hydrolyzes cholesterol from the membrane

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16
Q

Cholesterol is transported to what structure in the cell after release from the membrane?

A

Mitochondria

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17
Q

The side chain cleavage enzyme that converts cholesterol into pregnenolone (aka desmolase)

A

CYP450scc

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18
Q

The two steps involved in side chain cleavage of cholesterol

A
  1. Hydroxylations at C20 and C22

2. Side chain cleavage to get C21 pregnenolone

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19
Q

Key branching point for the formation of ALL steroid hormones is what structure?

A

Pregnenolone (C21)

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20
Q

Pregnenolone can be modified to form what three classes of steroids?

A

Mineralcorticoids, glucocorticoids, and androgens

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21
Q

If 17-hydroxylation of pregnenolone occurs first, what steroid hormones are created?

A

Androgens (Androstene), and Glucocorticoids (Cortisol)

22
Q

All steroid hormones undergo which enzyme?

A

3-beta-dehydrogenation/isomerization

23
Q

What enzyme is particular to only mineralcorticoids?

A

18 hydroxylation

24
Q

Which enzyme in steroid synthesis is a dual function enzyme?

A

CYP450c17

25
Q

What is the action of CYP450c17

A
  1. Catalyzes 17-hydroxylation

2. Catalyzes 17,20 lyase activities

26
Q

Mineralcorticoids undergo enzymes of which numbers?

A

3 –> 21 –> 11 –> 18

27
Q

Glucocorticoids undergo enzymes of which numbers?

A

3 –> 17 or P450c17 –> 21 –> 11

28
Q

Androgens undergo enzymes of which numbers?

A

17 or P450c17 –> 17,20 lyase or P450c17 –> 3

29
Q

What effect do statins have on the production of steroid hormones? (increase / decrease)

A

Decrease production

30
Q

Earliest committed step for mineralcorticoids?

A

21-hydroxylase

31
Q

Earliest committed step for glucocorticoids?

A

21-hydroxylase (other tract)

32
Q

Earliest committed step for androgens?

A

17,20 Lyase or second P450c17

33
Q

Androgens and estrogens are synthesized in the testes and ovaries via which two molecules?

A

Androstenedione and testosterone

34
Q

Which pathway is the most common pathway in the testes for the formation of androstenedione?

A

delta5 pathway

35
Q

Outline the delta-5 pathway in the testes

A
  1. Pregnelone undergoes 17-hydroxylation
  2. Then 17,20 lyase of 17-hydroxypregnenolone
  3. Then hydroxy dehydrogenation/isomerization to androstenedione
36
Q

How is testosterone metabolized?

A

Via 17-oxidation and 5alpha-reduction

37
Q

How many ketosteriods are produced in peripheral tissues?

A

17

38
Q

How is dihydrotestosterone (DHT) produced from testosterone, and what enzyme is involved?

A

5alpha reduction of the double bonded ring of testosterone by a 5alpha reductase in the periphery

39
Q

What is the most abundant form form of estrogen?

A

17beta-estradiol (*diol means two OH groups)

40
Q

What are estrogens derived from, and by which complex?

A

Derived from androgens via the aromatase complex

41
Q

Estrone is formed via the aromatization of which molecule?

A

Androstenedione

42
Q

17beta-estradiol is formed via the aromatization of which molecule?

A

Testosterone

43
Q

How many hydroxylations are involved in the aromatase complex, and what are the cofactors?

A

Three hydroxylations via NADPH and O2

44
Q

What molecule is the key branch point in the formation of estrogens?

A

Androstenedione

45
Q

What tissue is progesterone manufactured?

A

Corpus luteum

46
Q

Progesterone is taken up by the _______ cells to produce ________ and __________

A

theca cells to produce androstenedione and testosterone

47
Q

Once testosterones are created from progesterone, they are secreted and picked up by _________ cells, which express ______ to make estriol and estrone

A

granulosa cells which express aromatase

48
Q

What is the structural difference between mineralcorticoids and glucocorticoids?

A

Glucocorticoids have an 18-hydroxyl group

49
Q

Mineralcorticoids go through the _______ step first, because they don’t have a 17-hydroxyl

A

Isomerase

50
Q

Glucocorticoids and androgens go through the _______ step first

A

17-hydroxylation

Biochem II (7 decks)

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