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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
Which protein regulates cholesterol and fatty acid levels?
SREBP 1c
26
What is the purpose of SREBP 1c?
Regulation of cholesterol and fatty acid synthesis
27
What is the purpose of bile acids?
Solubilising Cholesterol
28
Testosterone and Estradiol are synthesised in which organs?
The gonads
29
Which two cholesterol based **steroid hormones** are synthesised in the **gonads**?
Testosterone Estradiol
30
In which organs are the hormones Cortisol and Aldosterone synthesised?
The Adrenal glands
31
Which **enzymes** are largely responsible for **steroidogenesis**?
Cytochrome P450 Monooxygenase
32
What is the purpose of **Cytochrome P450 Monooxegenase**?
Mediates Steroidogenesis
33
What is the name of the **21-Carbon precursor** of all **steroid hormones**?
Pregnenolone
34
What is the molecule Pregnenolone used for in the body?
Steroid hormone synthesis
35
What are the three main groups of steroid hormones?
Corticosteroids Androgens Oestrogens
36
What **precursor** molecule is required in order to form **Oestrogen**?
Testosterone
37
In which organ does the **conversion** of **cholesterol** to **corticosteroids** take place?
The Adrenal Glands
38
Which of the layers of the **adrenal cortex** is the most **external**? Zona Glomerusa Zona Reticularis Zona Fasciculata
Zona Glomerusa
39
Which of the below is the innermost layer of the **adrenal cortex**? Zona Glomerusa Zona Reticularis Zona Fasciculata
Zona Reticularis
40
Which of the below layers is the **middle** of the **adrenal cortex**? Zona Glomerusa Zona Reticularis Zona Fasciculata
Zona Fasciculata
41
In which adrenal cortex layer are mineralcortocoids generally produced?
Zona Glomerusa ## Footnote *Outermost*
42
In which Adrenal Cortex layer are glucocortocoids generally produced?
Zona Fasciculata ## Footnote *Middle*
43
In which layer of the Adrenal Cortex are precursors for androgens (Sex Hormones) generaly produced?
Zona Reticularis ## Footnote *Innermost*
44
Depletion of which type of cortocoid is conisdered the most high-risk?
Mineralcortocoids
45
Which type of **corticosteroid** acts as an **anti-inflammatory agent** and **analgaesia**?
Glucocortocoids
46
Which zone of the Adrenal Cortex will be affected by the loss of pituitary hormones?
Zona Fasciculata Zona Reticularis
47
Problems affecting **which layer** of the adrenal cortex can precipitate **life-threatening hypoglycaemia** in the fasting state?
Zona Fasciculata ## Footnote *Middle*
48
What is the rate-limiting step of steroidogenesis?
Conversion of Cholesterol to Pregnenolone
49
Which hormone is released by the Zona Glomerulosa of the Adrenal Medulla, causing an increase in blood pressure?
Aldosterone
50
ACE converts what molecule to what form in the lungs?
Angiotensin-I to Angiotensin-II
51
Which hormone is downregulated by an ACE-inhibitor drug?
Aldosterone
52
Aldosterone causes:
Increase in blood pressure
53
**C-19 Aromatase** converts which hormone to which product?
Testosterone to Oestrogen
54
17a-Hydroxylase deficiency results in increased production of what type of steroid hormone?
Mineralocortocoids
55
Deficiency of which enzyme constitutes the most common type of adrenogenital syndrome?
21a-Hydroxylase
56
Hypertension and masculinisation is a result of a deficiency of which corticosteroid enzyme?
11ß-Hydroxylase
57
11ß-Hydroxylase is responsible for forming which steroid hormone products?
Mineralocortocoids Glucocortocoids
58
Inhibition of the function of **11ß-Hydroxylase** channels steroid production to which end product?
Sex hormones
59
17a-Hydroxylase is essential to providing precursors for which type of steroid hormones?
Sex Hormones
60
Blockage of either of which enzymes can cause marked decrease in Corticosteroids?
21a-Hydroxylase 11ß-Hydroxylase
61
In addition to blocking production of sex hormones, **deficiency of 17a-Hydroxylase** causes marked decrease in which **Corticosteroid**?
Glucocortocoids
62
How are steroids excreted from the body?
In the urine
63
Free cholesterol, when not being used for steroidogenesis, is converted to what?
Cholesterol Esters

Biochemistry (13 decks)

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