biochemistry 8

Question 1

what is the negative feedback loop in the endocrine system

Answer 1

neural/ chemical stimulus –> endocrine organ –> hormone –> target organ —> biochemical/ physiological effect

Question 2

how is cortisol produced in the body

Answer 2

1) hypothalamus secretes CRH
2) CRH stimulates anterior pituitary gland to release corticotropin (ATCH)
3) corticotropin stimulates adrenal cortex cortisol production by:

1) - Corticotropin interacts with G-protein-coupled receptors
2) Stimulates cAMP production
3) Activates cholesterol esterase
4) Cholesterol esters → FFA + Cholesterol
5) Cholesterol –> Cortisol

Question 3

how is negative feedback used in the production of cortisol

Answer 3

• cortisol from adrenal cortex suppresses CRH and ATCH secretion

Question 4

how is testosterone produced In the body

Answer 4

1) hypothalamus secretes gonadotropin releasing hormone (GnRH)
2) GnRH stimulates pituitary FSH and LH release
3) LH stimulates Leydig Cell Testosterone production via

1) LH interacts with a G protein–coupled receptors
2) Increase cAMP → Activate PKA
3) Activates cholesterol modifying enzymes
4) Cholesterol –> Testosterone

Question 5

how is negative feedback used in testosterone production

Answer 5

• testosterone from leydig cells suppress secretion from hypothalamus and pituitary
• extra negative feedback of pituitary by FSH and testosterone stimulated sertoil cells and inhibin

Question 6

how is oestradiol produced in the body

Answer 6

1) hypothalamus secretes GnRH
2) GnRH stimulates pituitary FSH and LH release
3) FSH stimulates ovarian E2 - oestradiol production
4) LH levels stimulate ovulation

Question 7

how is negative feedback used in E2 production

Answer 7

• E2 secreted by ovaries suppresses secretion from hypothalamus and pituitary
• extra negative feedback of pituitary by E2 stimulated follicle inhibin release

Question 8

what are the 5 main classes of signalling molecules and how are they used in the body

Answer 8

• progestogen - prepare muscles for implantation and supports pregnancy
• androgens - male sexual behaviours and lean muscle mass
• oestrogen - female sex characteristics
• glucocorticoids - glucose and glycogen synthesis and inhibits the inflammatory response
• mineralocorticoids - regulates salt balance and blood volume and pressure

Question 9

how is cholesterol synthesised into pregnenolone

Answer 9

• Cytochrome P450 enzymes (CYP) catalyze two hydroxylations (OH)
• Requires NADPH
• Cleaved by cholesterol 20,22-desmolase

Question 10

how is pregnenolone converted into various steroid hormones

Answer 10

via hydroxylation and Lyase Glucocorticoid to Androgen

Question 11

what occurs when oestrogen binds to an oestrogen receptor

Answer 11

• has zinc based DNA binding domains
• binds to oestrogen response element on DNA
• ligand binding causes a structure change
• structure change enables transcriptional regulator recruitment
• coactivators stimulate transcription

Question 12

what does tamoxifen do

Answer 12

• anti cancer drug
• inhibits cell growth
• bind to the pocket normally occupied by estradiol
• tramoxifen extends from this pocket

Question 13

what ate the causes, symptoms and treatment of cushings syndrome

Answer 13

causes - cortisol over production or exposure
symptoms - obesity, high blood pressure, high blood sugar, skin bruises easily, muscle weakness
treatment - remove source of cortisol

Question 14

what are the causes, symptoms and treatment o Addisons disease

Answer 14

causes - low aldosterone and cortisol due to an autoimmune disorder and adrenal gland disfunction

symptoms - weight loss, fatigue, abdominal pain, dark parches on skin, low blood pressure

treatment - aldosterone and cortisol hormone replacement

Question 15

what is the causes, symptoms and treatments of androgen excess

Answer 15

causes - high androgen from polycystic ovaries

symptoms - irregular periods, excess hair growth, weight gain, thinning hair oily skin or acne

treatment - antiandrogens

Question 16

what are the causes, symptoms and treatments of congenital adrenal hyperplasia

Answer 16

causes - glucocorticoid deficiency

symptoms - increased androgen causing enlarged adrenal gland, atypical genitalia, body less able to deal with stress, poor salt retention

treatment - cortisol/ aldosterone HRT, genital surgery, salt supplements

Question 17

what are the causes, symptoms and treatments of menopause

Answer 17

causes - decreased oestrogen - hypothalamus related from inhibitory influences, pituitary activity increases which increases FSH and LH

symptoms - end of menstruation, unpleasant physical and emotional symptoms

treatment - oestrogen and progesterone replacement. increase calcium to reduce bone loss

Question 18

what are agonists

Answer 18

activates nuclear hormone receptors

Question 19

what are antagonists

Answer 19

inhibits nuclear hormone receptors

Question 20

what are the two main classes of steroid hormones

Answer 20

• corticosteroids
• anabolic steroids

Question 21

what are corticosteroids and how do they work

Answer 21

• artificial version of adrenal gland hormone
• reduces immune system activity and decreases inflammation

Question 22

what are corticosteroids used to treat

Answer 22

• Asthma
• Chronic obstructive pulmonary disease
• Hay fever, hives and eczema
• Pain
• Inflammatory bowel disease
  e.g. Crohn’s disease
• Lupus
• Multiple sclerosis (MS)

Question 23

what are anabolic steroids and what are the used for

Answer 23

• synthetic hormone that mimics testosterone
• promotes an increase in muscle size

Question 24

what are anabolic steroids used to treat

Answer 24

• Hormone problems in men
• Delayed puberty
• Muscle loss from disease

Question 25

what are the high dosage dangers of anabolic steroids

Answer 25

• Acne, increase aggression, mood swings, paranoia
• In males; decrease libido, decrease testicle size and lower sperm counts.
• In females; increase libido, loss of breasts, facial hair growth, hair loss, irregular periods.
• High cholesterol, increase heart attack/strokes, Liver and kidney problems