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PL2002 > Steroids > Flashcards

Steroids Flashcards

1
Q

What do steroids act as?

A

Hormones and surfactants

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2
Q

What are steroids derived from?

A

Triterpenoids

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3
Q

How many isoprene units are in farnesyl pyrophosphate?

A

3

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4
Q

How is squalene oxide formed?

A

Squalene + O2 + NAPDH

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5
Q

Why are epoxides reactive?

A

Very strained angles

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6
Q

Why can squalene oxide ring close?

A

Rotatable bonds allow a cascade of electrons

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7
Q

What carbocation is most stable?

A

Tertiary carbocation

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8
Q

What are anti-migrations?

A

Each group migrates axially and is anti-periplanar to the one before

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9
Q

Why is ring-closed squalene likely to occur?

A

Due to stable tertiary carbocation and chair, boat, chair conformation of 6 membered ring

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10
Q

Lanesterol to cholesterol

A

Alkene reduced, new alkene introduced and methyl groups lost to form CO2

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11
Q

Structure of all steroids

A

3 - 6 membered rings
1 - 5 membered ring

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12
Q

Ring junctions in steroids

A

All ring junctions are trans except A/B rings which can be cis or trans

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13
Q

What is the structural drawing of ring junctions?

A

Trans - groups attached on opposite faces
Cis - groups attached on the same face

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14
Q

What are sterols?

A

Steroids with an alcohol

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15
Q

What are the origins of saponins?

A

Plant origin

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16
Q

What is the structure of saponins?

A

Extra 5-membered ring and spiroketal attached to extra ring

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17
Q

Why are saponins like surfactants?

A

Sugar units act as surfactants as they dissolve in water but the saponin rings are lipophilic

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18
Q

What do saponins cause?

A

Haemolysis

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19
Q

What is the ring conformation of cardioactive glycosides?

A

Cis fused ring system between C/D and A/B

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20
Q

What is the additional ring on cardioactive glycosides?

A

Unsaturated lactone at C-17β

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21
Q

What is digitoxigenin?

A

A cardioactive glycoside used as arrow poison

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22
Q

Why are cardioactive glycosides cardioactive?

A

Sugar unit increases solubility and binding to heart muscle

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23
Q

Why do bile acids occur in salt form?

A

Carboxylic acids so form bile salts

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24
Q

What groups are on bile acids?

A

3a & 7a OH’s
C5 carboxylic acid side chain

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25
Q

What are the 2 types of hormones?

A

Sex and adrenocortical

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26
Q

Where are adrenocortical hormones produced?

A

Adrenal cortex

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27
Q

What are the 2 types of adrenocortical hormones?

A

Glucocorticoids and mineralocorticoids

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28
Q

Structure of glucocorticoids?

A

C21 pregnane structure
17β ketone group with OH
11β OH
Conjugation in A ring with =O

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29
Q

Structure of mineralocorticoids?

A

C21 pregnane sgtrucutre
17β ketone group
13β COOH
Conjugation on A ring with =O

30
Q

What do mineralocorticoids do?

A

Control electrolyte balance in kidneys
Retention of Na+/Cl-
Excretion of K+

31
Q

How is H2O solubility of steroids increased?

A

Addition of OH and ionised groups

32
Q

How are steroids transported?

A

Attached to a large protein
Bond to a small compound such as a sugar or salt

33
Q

What is pinocytosis?

A

Cell takes up fluid along with small dissolved molecules

34
Q

What is the process when steroids pass through cell membrane?

A

Steroid diffuses through cell membrane
Attaches to steroid receptor complex
Dimerises
Translocates to nucleus
Binds to chromatin and alters DNA and cell function

35
Q

What does Sex Hormone Binding Globulin transport?

A

Testosterone and estradiol

36
Q

What does corticosteroid-binding Globulin transport?

A

Hydrocortisone, aldosterone and progesterone

37
Q

What do LDL contain?

A

LDL contains higher levels of cholesterol and triglycerides

38
Q

Why are LDL light?

A

Contains hydrocarbons

39
Q

How many times more cholesterol does LDL have than HDL?

A

4x

40
Q

What is Phase I of cholesterol metabolism?

A

Oxidation using CYP450
Alkyl groups lost and COOH formed - polar
Reduction of double bond - gives A/B ring cis geometry

41
Q

What is Phase II of cholesterol metabolism?

A

Addition of polar groups glycine or taurine

42
Q

Where is cholesterol metabolised?

A

Liver

43
Q

Where are bile salts stored?

A

Gallbladder

44
Q

Why are bile salts surfactants?

A

OH groups on alpha face and methyl groups on beta face

45
Q

What % of bile salts are recycled?

A

95%

46
Q

How many times can each bile salt molecule be reused?

A

20x

47
Q

What controls stock of bile salts?

A

Enterohepatic recycling

48
Q

What are the therapeutic properties of glucocorticoids?

A

Diseases with overactive immune system
Reduces swelling, heat and tenderness in cancer treatment

49
Q

What is transactivation with Glucocorticoids?

A

GC binds to cytosolic GC receptors
Receptor-ligand complex translocates to cell nucleus
Binds to GCR elements
Results in regulation of gene expression

50
Q

What are the effects of proteins that result from transactivation of glucocorticoids?

A

Anti-inflammatory
Increases gluconeogenesis

51
Q

What is gluconeogenesis?

A

Glucose synthesis from proteins and fats

52
Q

What is transrepression with Glucocorticoids?

A

GCRs inteact with specific transcription factors
Prevents transcription of pro-inflammatory genes including cytokines and chemokines

53
Q

What is a negative effect of GCs?

A

GCs can affect wanted and unwanted (regulatory) genes

54
Q

How do GCs immunosupress?

A

Suppress cell mediated immunity
Suppresses gene code for cytokines
Reduces T cell proliferation
Can induce T cell apoptosis

55
Q

How do GCs have an anti-inflammatory effect?

A

Potent
Inhibit prostaglandins and leukotrienes
Supress COX I and COX II expression

56
Q

How does the hydrocortisone negative feedback loop work?

A

Low hydrocortisone levels stimulate corticosteroid releasing factor
Stimulates ACTH from pituitary
ACTH stimulates biosynthesis of hydrocortisone

57
Q

Where is corticosteroid releasing factor released from?

A

Hypothalamus

58
Q

What happens when hydrocortisone levels are high?

A

CRF and therefore ACTH are not produced

59
Q

Side effects of glucocorticoids

A

Weight gain
Irregular periods
Cataracts
Increased skin fragility

60
Q

Side effects of mineralocorticoids

A

Hypertension
Salt and Water retention

61
Q

What does conjugation of A ring in corticosteroids do?

A

Increases glucocorticoid
activity over mineralocorticoid

62
Q

Halogenation in corticosteroids?

A

increases both gluco &
mineralocorticoid activity

63
Q

Addition of sodium phosphate in corticosteroids

A

Increases aqueous solubility for IV

64
Q

Methylation at 16 in corticosteroids?

A

increases glucocorticoid
activity but not mineralocorticoid

65
Q

What effect do synthetic progestins have on hypothalamus?

A

Feedback effect prevents ovulation and stops uterine contractions

66
Q

How can estrogen be improved?

A

Alkylate phenol on ring A to create prodrug
Alkylate c17 to prevent OH becoming ketone

67
Q

What are the key functional groups on oestrogens?

A

No side chain
Aromatic Ring A
No methyl group at C10
Ketone or OH at C17

68
Q

What are the key functions on progestogens?

A

Side chain at C17
Conjugation with A ring and =O

69
Q

What are the key functions on androgens?

A

No side chain
Conjugation with A ring and =O
17β-OH

70
Q

What is estrogen metabolised to?

A

Estriol and estrone

71
Q

How is progesterone altered to be suitable for oral use?

A

Addition of Me at C6
Elongate side chain at C13

72
Q

What is Mestranol a pro-drug of?

A

Ethinylestradiol

PL2002 (7 decks)

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