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What is the structure of Cholesterol?
- Made of 4 steroid rings
- 1 OH, 2 Methyl group and a branched hydrocarbon chain
- of 250 possible stereoisomers, only one in nature
- Only found in Animals
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What is the 1st committed step of Cholesterol synthesis?
What is the enzyme? What else is needed? What inhibits it?
Mevalonic acid synthesis (it is the regulatory step )
- HMG-CoA Reductase
- 2NADPH
- High levels of Cholesterol
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What is Mevalonate converted to (in order)?
Isopentenyl pyrophosphate (5C) and Dimethylallyl pyrophosphate (5)
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How is cholesterol synthesis regulated?
HMG-CoA reductase is :
- Inhibited: It is inhibited be high levels of Cholesterol.( both genetically and covalently), low energy and high Glucagon, high AMP
- also some statin drugs via reversible compettition: lova,simva and mevastatin
- Promoted: Insulin promotes HMG-CoA reductase production
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Isoprenoids. What do they stem from and what are the principle ones?
- Stem from Isopentenyl-PP and Dimethylallyl-PP
- The principle ones are:
- Ubiquinone- electrone transport
- Dolichol-
- Side chain of heme A
- Farnesyl (15C)/Geranyl (10) - are precursers of cholesterol and are membrane protein anchors
All of our fat-soluble Vitamins (A,D,E,K)
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What does Farnesyl transferase do?
- It moves farnesyl to the protein and attaches them together.
- This transferase is targeted in cancer chemo theropy to interfer with cancer growth.
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What FA accumulates in Refsums disease?
Phytanic acid
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Vitamin D
- is a prohormone
- functions in: Regulates Ca and P metabolism
- Cholesterol is a precursor to it.
- it arises from 7-dehydrocholesterol
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Bile Salts
- Are derived from Cholesterol.
- since the body cannot dispose degrade steroids the body disposes of them via the bililary system.
- bile salts are: glycocolic acid and taurocholic acid.
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The 3 phosphates on IP3 come from?
2 from ATP and one for the original phosphatidic acid
Thank you Zenia
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