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part I > steroids and prostaglandins (biochem) > Flashcards

steroids and prostaglandins (biochem) Flashcards

1
Q

cholesterol
- structure
- no. of carbons
- how is it transported

A
  • ring-based
  • 27 carbon atoms
  • by lipoproteins (LDL, HDL)
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2
Q

where is cholesterol synthesised?

pathway name

A

endoplasmic reticulum

HMG-CoA

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3
Q

what subclass of receptor are steroid receptors?

which protein are they associated with?

A

nuclear receptors

heat shock protein (HSP)

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4
Q

which receptors do steroids act on?

what do they do for gene transcription?

A

nuclear receptors

increase it

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5
Q

what type of hormones are steroids and prostaglandins?

A

lipid hormones

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6
Q

2 classifications of steroid hormones
where is each synthesised?

A

corticosteroids
- synthesised in adrenal cortex

gonadal steroids
- synthesised in ovary or testis

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7
Q

what are steroid hormones derrived from?

A

cholesterol
(by removal of carbon groups and addition of oxygen-containing groups)

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8
Q

3 subtypes of corticosteroids & major example of each

A

mineralocorticoids e.g. aldosterone
glucocorticoids e.g. cortisol
androgens e.g. DHEA

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9
Q

3 subtypes of gonadal steroids and example of each

A

progestogens e.g. progesterone
androgens e.g. testosterone
estrogens e.g. estradiol

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10
Q

steroid genenis diagram

A
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11
Q

what is the rate limiting step in steroid genesis?
which enzyme is involved?

A

cholesterol (C27)–> progestogens (C21) + C6

CYP11A1 (a cytochrome p450)
aka CP450 CSCC (cholesterol side chain cleavage)

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12
Q

where does CYP11A1 reside?

which 2 substances do its actions depend on?

A

inner mitochondria facing matrix

StAR
mitochondrial peripheral benzodiazepine receptors

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13
Q

what is the role of StAR?

where does it reside?

A

aids with intracellular transport of hydrophobic cholesterol

ovaries and testes

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14
Q

2 steroidogenic enzymes:

A
  1. cytochrome p450 (specifically CYP11A1/ CP450 CSCC (cholesterol side chain cleavage)
  2. HSD
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15
Q

which 2 enzymes does cytochrome p450 include?

A

17- hydroxylase

21 hydroxylase

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16
Q

what are the 4 types of gonadal cells?

A

Leydig cells
theca cells
granulosa cells
luteal cells

17
Q

what do Leydig cells produce?

do they have 17B-HSD?

A

testosterone

no

18
Q

what do theca cells produce?

do they have 17B-HSD?

A

androgens - but cannot produce testosterone and oestradiol

yes

19
Q

what do granulosa cells produce?

do they have 17B-HSD?

A

oestradiol

yes

20
Q

what do luteal cells produce?

A

progesterone & oestradiol

21
Q

CAH - congenital adrenal hyperplasia

  1. inheritance
  2. what is the issue?
  3. what is the consequence of this physiologically
A
  1. autosomal recessive
  2. defect in StAR protein (also cytochrome p450CSCC and 21-hydroxylase)
  3. failure of steroid production
    accumulation of large lipid droplets in adrenal glands
22
Q

clinical features of congenital adrenal hyperplasia (CAH)

A

salt wasting crisis
issues with lung inflation

also:
i. ambigious genitalia
ii. natiuresus (weeing out lots of sodium)
iii. precocious puberty or failed puberty
iv. infertlility due to anovulation
v. virilisation
^^ all above due to 21-hydroxylase deficiency
vi. HTN
^^ due to 11-hydroxylase deficiency

23
Q

what are prostaglandins synthesised from?

A

arachadonic acid

24
Q

what is arachadonic acid?

what is it attached to?
which enzyme removes it from this?

A

(the material from which prostaglandins are synthesised)
- a polyunsaturated fatty acid

phospolipid membrane

phospholipase A2 - this is rate limiting step in synthesis of prostaglandins

arachadonic acid –> free arachidonate

25
Q

what limits phospholipase A2?

A

lipocortin

26
Q

what does COX do?

A

free arachidonate –> prostaglandin H2 (briefly G2 first)

27
Q

what is the difference between COX1 and COX2

A

COX 1 - constitutively active
COX 2 - hormone responsive

28
Q

what inhibits COX?

A

indomethacin
aspirin
other NSAIDS

29
Q

what does prostaglandin rely on?

A

alcohol group at carbon 15

30
Q

what enzyme can inhibit prostaglandin?

where is there lots of this?

A

15-hydroxyprogestaglandin dehydrogenase

lungs

31
Q

myometrial contraction is a balancing act.

what are the relaxants/ contractants

A

contractants (Ca2+)
oxytocin
prostaglandins

relaxants (cAMP/ cGMP)
NO
relaxin
progesterone

part I (12 decks)

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