Biochemistry: Lect 3.

Question 1

Which of the following is NOT considered one of the six main steroid hormones in humans according to the source?
a) Progesterone
b) Cortisol
c) Melatonin
d) Estradiol

Answer 1

c) Melatonin

Steroid hormones:
Progesterone
Aldosterone
Cortisol
Estradiol
Calcitrol
Testosterone

Question 2

All of the main steroid hormones in humans, except which one, are derived from cholesterol via pregnenolone?
a) Aldosterone
b) Calcitriol
c) Testosterone
d) Cortisol

Answer 2

b) Calcitriol

Question 3

The conversion of pregnenolone to which steroid hormone is a frequent step in many steroid syntheses?
a) Aldosterone
b) Cortisol
c) Progesterone
d) Estradiol

Answer 3

c) Progesterone

Question 4

Which class of steroid hormones is primarily synthesized in the adrenal cortex?
a) Androgens and estrogens
b) Progestagens and androgens
c) Mineralocorticoids and glucocorticoids
d) Estrogens and mineralocorticoids

Answer 4

c) Mineralocorticoids and glucocorticoids

Question 5

Refer to the diagram outlining steroid hormone synthesis [Consult source page likely containing a synthesis pathway diagram]. The conversion of pregnenolone to progesterone involves which enzyme(s)?
a) 17α-hydroxylase
b) Aromatase
c) 3β-hydroxysteroid dehydrogenase and Δ5,4 isomerase
d) 21-hydroxylase

Answer 5

c) 3β-hydroxysteroid dehydrogenase and Δ5,4 isomerase

Question 6

Which of the following is the most important glucocorticoid?
a) Aldosterone
b) Corticosterone
c) Cortisol
d) Deoxycortisone

Answer 6

c) Cortisol

Question 7

Glucocorticoids are C21 steroids that are key regulators of which metabolic process?
a) Fatty acid synthesis
b) Protein synthesis
c) Glucose metabolism
d) Electrolyte balance

Answer 7

c) Glucose metabolism

Question 8

Cortisol is primarily made by which zone of the adrenal cortex?
a) Zona glomerulosa
b) Zona fasciculata
c) Zona reticularis
d) Adrenal medulla

Answer 8

b) Zona fasciculata

Question 9

According to the source, cortisol has which of the following effects on glucose metabolism?
a) Decreases gluconeogenesis
b) Increases glucose uptake by non-muscle tissue
c) Decreases lipolysis
d) Increases gluconeogenesis

Answer 9

d) Increases gluconeogenesis

Other effects:
Increases hunger, increase lipolysis and protein degeneration, decrease uptake of glucose

Question 10

Prolonged exposure to cortisol can lead to which of the following conditions mentioned in the source?
a) Addison’s disease
b) Hypothyroidism
c) Cushing’s disease

Answer 10

c) Cushing’s disease

Other conditions:
Diabetes mellitus
Impaired wound healing
Infections

Question 11

The circadian pattern of cortisol release results in higher levels at what time?
a) Late afternoon
b) Early evening
c) After sleeping
d) Midnight

Answer 11

c) After sleeping

Question 12

Which of the following is the major mineralocorticoid hormone?
a) Cortisol
b) Corticosterone
c) Aldosterone
d) Progesterone

Answer 12

c) Aldosterone

Question 13

As a mineralocorticoid, aldosterone primarily regulates the concentration of which substances?
a) Glucose and potassium
b) Sodium and glucose
c) Mineral concentrations
d) Calcium and phosphate

Answer 13

c) Mineral concentrations

Other regulations:
increase K+ excretion and blood pressure
Promote Na+ concentration

Question 14

Aldosterone promotes sodium reabsorption via which mechanism in the kidneys?
a) Increasing glomerular filtration rate
b) Inhibiting sodium channels in the nephron
c) Stimulating Na+/K+ ATPases and Na+ channels
d) Decreasing the activity of the renin-angiotensin system

Answer 14

c) Stimulating Na+/K+ ATPases and Na+ channels

Question 15

Refer to the diagram illustrating mineralocorticoid synthesis [Consult source page likely containing a synthesis pathway diagram]. Which enzyme is unique to aldosterone synthesis in the zona glomerulosa?
a) 21-hydroxylase
b) 11β-hydroxylase
c) 17α-hydroxylase
d) 18-hydroxylase/aldosterone synthase

Answer 15

d) 18-hydroxylase/aldosterone synthase

NOTE: Apart of the P450 aldosterone system w/ 18 dehydrogenase

Question 16

Refer to the diagram illustrating mineralocorticoid synthesis [Consult source page likely containing a synthesis pathway diagram]. Explain the synthesis pathway diagram . Familiarize yourself with the structures.

Question 17

How is cortisol primarily transported in the blood?
a) Bound to albumin
b) As a free hormone
c) Bound to α-globulin transcortin
d) Bound to sex hormone-binding globulin (SHBG)

Answer 17

c) Bound to α-globulin transcortin

Note: Deoxycotersterone and Progesterone also is trasported but in small amounts
Aldosterone — 50-65% is transports via the transcortin and globulin and the rest is free in blood.

Question 18

Which of the following is the most important circulating androgen?
a) Dehydroepiandrosterone (DHEA)
b) Androstenedione
c) Testosterone
d) Dihydrotestosterone (DHT)

Answer 18

c) Testosterone

Question 19

Dehydroepiandrosterone (DHEA) is primarily synthesized in which zones of the adrenal cortex?
a) Zona glomerulosa only
b) Zona fasciculata only
c) Zona fasciculata and (mainly) reticularis
d) All three zones of the adrenal cortex

Answer 19

c) Zona fasciculata and (mainly) reticularis

Question 20

Testosterone is primarily synthesized in which cells of the testes?
a) Sertoli cells
b) Leydig interstitial cells
c) Germ cells
d) Myoid cells

Answer 20

b) Leydig interstitial cells

Question 21

Refer to the diagrams illustrating androgen synthesis pathways [Consult source page likely containing synthesis pathway diagrams]. Which of the following pathways for testosterone synthesis is considered more prominent in humans?
a) Δ4 or progesterone pathway
b) Δ5 or dehydroepiandrosterone (DHEA) pathway
c) Both pathways are equally prominent
d) The pathway involving aldosterone as an intermediate

Answer 21

b) Δ5 or dehydroepiandrosterone (DHEA) pathway

Question 22

What enzyme converts testosterone to its more active form, dihydrotestosterone (DHT)?
a) Aromatase
b) 17β-hydroxysteroid dehydrogenase
c) 5α-reductase
d) 17,20-lyase

Answer 22

c) 5α-reductase

Question 23

According to the source, what is a potential negative impact of regular nandrolone use on the male reproductive system?
a) Increased sperm count
b) Decreased risk of prostate enlargement
c) Shrunken testes
d) Enhanced libido

Answer 23

c) Shrunken testes

Other impacts:
Decrease sperm count
Enlarged prostate

Question 24

Which of the following is a C-18 steroid?
a) Progesterone
b) Testosterone
c) Estradiol
d) Cortisol

Answer 24

c) Estradiol

Question 25

Which of the following is considered the primary human estrogen synthesized mainly by the ovaries? a) Estrone (E1) b) Estriol (E3) c) 17β-Estradiol (E2) d) Ethinyl estradiol

Answer 25

c) 17β-Estradiol (E2)

Question 26

Describe the Estrogen types, E1 and E3.

Answer 26

E1: — primary source of estrogen for other species — main source of estrogen in post menopausal females E3: — abundant in pregnant in placenta production — maintain healthy vagina tissues

Question 27

What enzyme complex catalyzes the aromatization of androgens to estrogens? a) 17β-hydroxysteroid dehydrogenase b) 3β-hydroxysteroid dehydrogenase c) Aromatase d) 5α-reductase

Answer 27

c) Aromatase

Question 28

Refer to the diagram illustrating estrogen synthesis. The conversion of androstenedione results in the formation of which estrogen? a) Estradiol (E2) b) Estriol (E3) c) Estrone (E1) d) Ethinyl estradiol

Answer 28

c) Estrone (E1)

Question 29

Refer to the diagram illustrating estrogen synthesis. The conversion of testosterone results in the formation of which estrogen? a) Estradiol (E2) b) Estriol (E3) c) Estrone (E1) d) Ethinyl estradiol

Answer 29

a) Estradiol (E2)

Question 30

In post-menopausal women, what is the major source of estrogens according to the source? a) Ovarian synthesis of estradiol b) Adrenal cortex production of estrogens c) Peripheral tissue aromatization of androgens d) Placental production of estriol

Answer 30

c) Peripheral tissue aromatization of androgens

Question 31

Aromatase inhibitors are used to treat some breast cancers in which group of women according to the source? a) Pregnant women b) Pre-menopausal women c) Post-menopausal women d) Women with estrogen receptor-negative tumors

Answer 31

c) Post-menopausal women

Question 32

Why are aromatase inhibitors generally not used to treat breast cancer in pre-menopausal women according to the source? a) Ovaries do not produce androgens in pre-menopausal women. b) Blocking aromatase in pre-menopausal women leads to increased ovarian stimulation and estrogen production. c) Aromatase is not active in peripheral tissues of pre-menopausal women. d) Aromatase inhibitors are ineffective in pre-menopausal women.

Answer 32

b) Blocking aromatase in pre-menopausal women leads to increased ovarian stimulation and estrogen production.

Question 33

According to the source, how do synthetic estrogens and progestins act as contraceptives? a) By increasing the rate of fertilization b) By preventing ovulation c) By promoting implantation of the fertilized egg d) By decreasing the production of gonadotropin-releasing hormone (GnRH)

Answer 33

b) By preventing ovulation by mimicking and producing natural amounts of estrogen and progesterone like in pregnancy

Question 34

Which protein facilitates the transport of gonadal hormones in the blood? a) Albumin b) Corticosteroid-binding globulin (CBG) c) Sex hormone-binding globulin (SHBG) d) Lipoproteins

Answer 34

c) Sex hormone-binding globulin (SHBG)

Question 35

According to the source, which of the following factors decreases the synthesis of SHBG? a) Estrogens b) Hyperthyroidism c) Obesity d) Hepatitis

Answer 35

C) Obesity Factors that increase: — estrogen, hyperthyroidism, liver disease Factors that decrease: — androgen, hypothyroidism, aging

Question 36

Refer to the diagrams illustrating androgen synthesis pathways [Consult source page likely containing synthesis pathway diagrams]. Discuss the pathway for both: A) Δ4 or progesterone pathway B) Δ5 or dehydroepiandrosterone (DHEA) pathway. Familiarize self with structures.