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Endocrine System > Synthesis of Steroid Hormones > Flashcards

Synthesis of Steroid Hormones Flashcards

1
Q

The steroid hormone-receptor complex enhances the synthesis of ______________ .

A

mRNA through transcription

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2
Q

Transcription of the human ______ gene encoding _______ in adult tissues is largely limited to the adrenal and gonad, although it may also be expressed in skin.

A

CYP17A1

P450c17

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3
Q

____________ are important beyond the context of male genital differentiation and androgen action.

A

5α-reductases

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4
Q

______________ mediate the interconversions of androstenedione and testosterone, DHEA and androstenediol, estrone and estradiol.

A

17β-hydroxysteroid dehydrogenases (17βHSDs)

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5
Q

Wich enzyme catalyze the following reactions?

  • Converts pregnenolone to progesterone
  • 17α-hydroxypregnenolone to 17α- hydroxyprogesterone (17OHP)
  • DHEA (dehydroepiandrostedione) to androstenedione
  • Androstenediol to testosterone
A

3βHSD

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6
Q

The _________ use NAD+ as their cofactor to oxidize hydroxysteroids to ketosteroids, and the __________ mainly use NADPH to reduce ketosteroids to hydroxysteroids.

A

Dehydrogenases

Reductases

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7
Q

The enzyme present in the Endoplasmic Reticulum that catalyzes 21- hydroxylation in the synthesis of both glucocorticoids and mineralocorticoids are:

A

P450c21

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8
Q

______________ result in the loss of all steroidogenesis, indicating that all steroidogenesis is initiated by this one enzyme.

A

P450scc mutations

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9
Q

________increasing blood sugar and acting as an immunosuppressant.

A

Cortisol (Glucocoticoid)

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10
Q

____________ activate molecular oxygen using their heme center and add electrons from the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH).

A

All P450 enzymes

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11
Q

What property made the stereoid hormones to diffuse through the cell membrane of the target cell), interacting once inside with soluble nuclear receptors?

A

Lipid Soluble

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12
Q

A cytochrome P450 may be either type 1 when its found in ______________

A

Mitochondria

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13
Q

__________ is the enzymatic rate- limiting step in steroidogenesis.

A

P450scc

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14
Q

_________ is the microsomal P450 enzyme that catalyzes both 17α- hydroxylase and 17,20-lyase activities, principally in the adrenal and gonads.

A

P450c17

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15
Q

The enzyme present in the Endoplasmic Reticulum that catalyzes aromatization of androgens to estrogens are:

A

P450aro

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16
Q

The first and rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone by which single enzyme?

A

P450scc (CYP11A1)

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17
Q

Within mitochondria, _________ is converted to _________ by an enzyme in the inner membrane called CyP11A1.

A

Cholesterol

Pregnelone

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18
Q

__________ is the first, rate-limiting, and hormonally regulated step in the synthesis of all steroid hormones. This process involves oxidative scission of the __________ to yield __________.

A
  • Conversion of cholesterol to pregnenolone in mitochondria
  • C20-22 bond
  • Pregnenolone
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19
Q

Steroid hormones are all synthesized from cholesterol and hence have closely related structures based on:

A

Cyclopentanophenanthrene 4-ring structure

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20
Q

In wich disorder affected females are phenotypically normal but fail to undergo adrenarche and puberty, and males have absent or incomplete development of the external genitalia?

A

Male Pseudohermaphroditism (46,XY disorder of sex development)

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21
Q

If it expresses the cholesterol side-chain cleavage enzyme, P450scc, which catalyzes the first step in steroidogenesis, is said that the cell is:

A

Steroidgenic

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22
Q

___________ is the cholesterol side-chain cleavage enzyme catalyzing the series of reactions formerly termed “20,22 desmolase.”

A

Mitochondrial P450scc

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23
Q

_________is expressed in steroidogenic tissues (ovarian granulosa cells, placenta), in brain, and in nonsteroidogenic tissues, especially fat and bone

24
Q

21- hydroxylase deficiency has an incidence of 1 in 15,000 to 1 in 20,000 births, causing more than 90% of all cases of:

A

Congenital Adrenal Hyperplasia (CAH)

25
Deficient **17α-hydroxylase** activity results in **decreased** in\_\_\_\_\_\_\_\_\_\_ and over prodction of \_\_\_\_\_\_\_\_\_\_\_.
Cortisol ACTH
26
\_\_\_\_\_\_\_\_\_ participate in regulating **CYP17A1 transcription**, linking the regulation of steroidogenesis with the regulation of cholesterol biosynthesis.
**SREBP1c**
27
Expression of **P450scc** is induced by:
**cAMP** in: * The adrenal zona fasciculata/reticularis * Testis and ovary And by the **calcium/protein kinase C system** in * Zona glomerulosa.
28
\_\_\_\_\_\_\_\_\_\_\_\_regulates the cyclical changes of the endometrium of the uterus, and the maintenance of pregnancy.
Progesterone
29
Because insufficient free cholesterol is available to P450scc, there is adrenal insufficiency, causin a disease named:
**Wolman Disease**
30
\_\_\_\_\_\_\_\_\_is derived from cholesterol, this has a double bond between carbons # 5 and 6
Pregnelone
31
\_\_\_\_\_\_\_\_\_\_ is rare cause of **glucocorticoid and mineralocorticoid deficiency** that may be fatal if not diagnosed early in infancy
**3βHSD deficiency**
32
* In **F****emales**: * May occur **clitoromegaly** and mild virilization because the fetal adrenal overproduces large amounts of DHEA, a small portion of which is converted to testosterone
**3βHSD deficiency**
33
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_is a generic term for a group of oxidative enzymes, all of which have about 500 amino acids and contain a single heme group.
**Cytochrome P450** (Because all absorb light at 450 nm)
34
Severe deficiency of \_\_\_\_\_\_\_decreases the secretion of cortisol, causing CAH and virilization of affected females. It results in accumulation of **11-deoxycortisol**, and the **defect in the 17-deoxy** pathway in the synthesis of corticosterone in the fasciculata leads to **overproduction of DOC**, potentially leading to **mineralocorticoid-based hypertension**.
**P450c11β**
35
A cytochrome P450 may be **type 2** when its found in \_\_\_\_\_\_\_\_\_\_\_\_\_\_
Endoplasmic Reticulum
36
The **final steps** in the synthesis of glucocorticoids and mineralocorticoids are catalyzed by wich two closely related **mitochondrial** enzymes?
**P450c11β** and **P450c11AS**
37
The receptor-steroid hormone complex travels into the nucleus and binds to a \_\_\_\_\_\_\_\_\_\_\_
Hormone- response element (**HRE**) of an **enhancer region on DNA**
38
\_\_\_\_\_\_\_\_ contributes to the development and maintenance of female secondary sex characteristics.
Estrogens
39
The absence of **17α-hydroxylase** and **17,20- lyase** activities in complete **P450c17** deficiency prevents:
The synthesis of adrenal and gonadal sex steroids
40
\_\_\_\_\_\_\_\_\_\_\_ moves this double bond from the B ring to carbons 4 and 5 in the A ring, forming Δ4 compounds.
3β-hydroxysteroid dehydrogenase/isomerase
41
Wich protein is only found in the **adrenals** and catalyzes the **21-hydroxylation** of the Δ4 steroids progesterone **to DOC** and **17OHP to 11- deoxycortiso**l in the biosynthesis of mineralocorticoids and glucocorticoids, respectively?
**P450c21**
42
\_\_\_\_\_\_\_\_\_ contributes to the regulation of blood pressure
Aldosterone
43
The enzyme present in the **Endoplasmic Reticulum** that catalyzes both **17α- hydroxylase** and **17,20-lyase activities** are:
**P450c17**
44
\_\_\_\_\_\_\_\_\_\_\_\_ may belong to either the aldo-keto reductase or short-chain dehydrogenase/reductase families.
**Hydroxysteroid Dehydrogenase**
45
\_\_\_\_\_\_\_\_\_\_ is a cytosolic reductive enzyme that uses NADPH as its cofactor to catalyze reductase activity.
**17βHSD type 1**
46
Extraglandular aromatase expression, especially in fat, can convert:
Androgens to Estrogens
47
The two isozymes of **mitochondria** that **catalyze 11β- hydroxylase, 18-hydroxylase, and 18-methyl oxidase activities** are:
**P450c11**: * P450c11β (11β-hydroxylase) * P450c11**AS** (aldosterone synthase)
48
\_\_\_\_\_\_\_\_\_\_\_\_\_\_do not have heme groups, and require NADH/NAD+ or NADPH/NADP+ as cofactors to either reduce or oxidize a steroid
**Hydroxysteroid dehydrogenases (HSDs)**
49
How many carbons have: * Corticosteroids * Androgens * Estrogens
* Corticosteroids (C-21) * Androgens (C-19) * Estrogens (C-18)
50
Most of the major biologically active steroid hormones are ___________ compounds.
Δ4
51
\_\_\_\_\_\_\_\_\_\_\_\_ are produced by the **aromatization of androgens**, including those derived from adrenal steroidogenesis, by a complex series of reactions catalyzed by \_\_\_\_\_\_\_\_\_\_\_.
Estrogens Aromatase P450aro
52
Wich is the rate limiting step of biosynthesis of streoid hormones?
The transport of **free cholesterol** from the **cytoplasm** into **mitochondria**
53
Who is the mmediate precursor for the synthesis of all of the steroid hormones?
Pregnelone
54
Once **pregnenolone** is produced from cholesterol, it may undergo **17α-hydroxylation** by ________ to converted to **progesterone** (first biologically important steroid in the pathway).
P450c17
55
\_\_\_\_\_\_\_\_\_\_ catalyzes both conversion of the hydroxyl group to a **keto group on carbon 3** and the **isomerization of the double bond from the B ring** (Δ5 steroids) **to the A ring** (Δ4 steroids).
**3βHSD**
56
Who transport the free cholesterol from **cytoplasm** to **membrane**?
StarD4
57
Who is responsible for the rapid transport of cholesterol from the **outer mitochondrial membrane** to the **inner mitochondrial membrane?**
**StAR**

Endocrine System (2 decks)

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