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Biochemistry > 2 Cholesterol and Steroids > Flashcards

2 Cholesterol and Steroids Flashcards

1
Q

What molecules insert themselves in the plasma membrane of cells to provide rigidity?

A

Cholesterol

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2
Q

Are humans able to metabolise the Sterol structure common to cholesterol and steroids?

A

No

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3
Q

How is Cholesterol excreted by the body?

A

By the liver as:

Bile acids

free cholesterol

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4
Q

What is the main site of cholesterol synthesis in the body?

A

The Liver

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5
Q

How many mols of Acetyl-CoA are required to synthesise one mol of Cholesterol?

A

18 mols

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6
Q

How many mols of ATP are consumed to produce one mol of Cholesterol?

A

36

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7
Q

From what molecule is the reducing power derived in the production of Cholesterol?

A

NADPH

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8
Q

Where is NADPH generated?

A

In the pentose phosphate pathway

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9
Q

Formation of Mevalonic Acid is the first step in what process?

A

Cholesterol Synthesis

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10
Q

From Acetyl-CoA, what is the first step in the biosynthesis of Cholesterol?

A

Formation of Mevalonic Acid

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11
Q

What is the rate limiting enzyme in the initial stages of cholesterol synthesis?

A

HMG-CoA Reductase

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12
Q

Where in the cell does the biosynthesis of Cholesterol take place?

A

The cytoplasm

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13
Q

Is the reaction from Acetyl-CoA to Mevalonate reversible or irreversible?

A

Irreversible

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14
Q

Which enzyme is the target of Statin drugs?

A

HMG-CoA Reductase

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15
Q

Which type of drugs reduce cholesterol by competitively inhibiting binding of HMG-CoA to the appropriate enzyme?

A

Statins

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16
Q

During Cholesterol biosynthesis, Mevalonate is then reacted to form:

A

Farnesyl Pyrophosphate

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17
Q

During biosynthesis of Cholesterol, what is the precursor to the formation of Farnesyl Pyrophosphate?

A

Mevalonate

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18
Q

Two Farnesyl Pyrophosphate molecules are fused to create which 30-carbon Cholesterol precursor molecule?

A

Squalene

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19
Q

The 30-Carbon molecule squalene is formed from two of which molecule?

A

Farnesyl Pyrophosphate

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20
Q

Cholesterol consists of how many carbons?

A

27

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21
Q

HMG-CoA reductase activity is increased or decreased by Insulin?

A

Increased

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22
Q

HMG-CoA Reductase activity is increased or decreased by Glucagon?

A

Decreased

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23
Q

What cell membrane feature allows transit of cholesterol from the blood to the cytoplasm?

A

The LDL receptor

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24
Q

What are the five stages of Atherosclerosis?

A

Tissue damage

Oxidised LDL enters

macrophages follow the LDL

Marcropages Become foam cells

Plaque forms or bursts

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25
Q

Which protein regulates cholesterol and fatty acid levels?

A

SREBP 1c

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26
Q

What is the purpose of SREBP 1c?

A

Regulation of cholesterol and fatty acid synthesis

27
Q

What is the purpose of bile acids?

A

Solubilising Cholesterol

28
Q

Testosterone and Estradiol are synthesised in which organs?

A

The gonads

29
Q

Which two cholesterol based steroid hormones are synthesised in the gonads?

A

Testosterone

Estradiol

30
Q

In which organs are the hormones Cortisol and Aldosterone synthesised?

A

The Adrenal glands

31
Q

Which enzymes are largely responsible for steroidogenesis?

A

Cytochrome P450 Monooxygenase

32
Q

What is the purpose of Cytochrome P450 Monooxegenase?

A

Mediates Steroidogenesis

33
Q

What is the name of the 21-Carbon precursor of all steroid hormones?

A

Pregnenolone

34
Q

What is the molecule Pregnenolone used for in the body?

A

Steroid hormone synthesis

35
Q

What are the three main groups of steroid hormones?

A

Corticosteroids

Androgens

Oestrogens

36
Q

What precursor molecule is required in order to form Oestrogen?

A

Testosterone

37
Q

In which organ does the conversion of cholesterol to corticosteroids take place?

A

The Adrenal Glands

38
Q

Which of the layers of the adrenal cortex is the most external?

Zona Glomerusa

Zona Reticularis

Zona Fasciculata

A

Zona Glomerusa

39
Q

Which of the below is the innermost layer of the adrenal cortex?

Zona Glomerusa

Zona Reticularis

Zona Fasciculata

A

Zona Reticularis

40
Q

Which of the below layers is the middle of the adrenal cortex?

Zona Glomerusa

Zona Reticularis

Zona Fasciculata

A

Zona Fasciculata

41
Q

In which adrenal cortex layer are mineralcortocoids generally produced?

A

Zona Glomerusa

Outermost

42
Q

In which Adrenal Cortex layer are glucocortocoids generally produced?

A

Zona Fasciculata

Middle

43
Q

In which layer of the Adrenal Cortex are precursors for androgens (Sex Hormones) generaly produced?

A

Zona Reticularis

Innermost

44
Q

Depletion of which type of cortocoid is conisdered the most high-risk?

A

Mineralcortocoids

45
Q

Which type of corticosteroid acts as an anti-inflammatory agent and analgaesia?

A

Glucocortocoids

46
Q

Which zone of the Adrenal Cortex will be affected by the loss of pituitary hormones?

A

Zona Fasciculata
Zona Reticularis

47
Q

Problems affecting which layer of the adrenal cortex can precipitate life-threatening hypoglycaemia in the fasting state?

A

Zona Fasciculata

Middle

48
Q

What is the rate-limiting step of steroidogenesis?

A

Conversion of Cholesterol to Pregnenolone

49
Q

Which hormone is released by the Zona Glomerulosa of the Adrenal Medulla, causing an increase in blood pressure?

A

Aldosterone

50
Q

ACE converts what molecule to what form in the lungs?

A

Angiotensin-I to Angiotensin-II

51
Q

Which hormone is downregulated by an ACE-inhibitor drug?

A

Aldosterone

52
Q

Aldosterone causes:

A

Increase in blood pressure

53
Q

C-19 Aromatase converts which hormone to which product?

A

Testosterone to Oestrogen

54
Q

17a-Hydroxylase deficiency results in increased production of what type of steroid hormone?

A

Mineralocortocoids

55
Q

Deficiency of which enzyme constitutes the most common type of adrenogenital syndrome?

A

21a-Hydroxylase

56
Q

Hypertension and masculinisation is a result of a deficiency of which corticosteroid enzyme?

A

11ß-Hydroxylase

57
Q

11ß-Hydroxylase is responsible for forming which steroid hormone products?

A

Mineralocortocoids

Glucocortocoids

58
Q

Inhibition of the function of 11ß-Hydroxylase channels steroid production to which end product?

A

Sex hormones

59
Q

17a-Hydroxylase is essential to providing precursors for which type of steroid hormones?

A

Sex Hormones

60
Q

Blockage of either of which enzymes can cause marked decrease in Corticosteroids?

A

21a-Hydroxylase

11ß-Hydroxylase

61
Q

In addition to blocking production of sex hormones, deficiency of 17a-Hydroxylase causes marked decrease in which Corticosteroid?

A

Glucocortocoids

62
Q

How are steroids excreted from the body?

A

In the urine

63
Q

Free cholesterol, when not being used for steroidogenesis, is converted to what?

A

Cholesterol Esters

Biochemistry (13 decks)

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