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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
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
- High levels of Cholesterol
What is Mevalonate converted to (in order)?
Isopentenyl pyrophosphate (5C) and Dimethylallyl pyrophosphate (5)
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
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
- 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)
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.
What FA accumulates in Refsums disease?
- is a prohormone
- functions in: Regulates Ca and P metabolism
- Cholesterol is a precursor to it.
- it arises from 7-dehydrocholesterol
- 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.
The 3 phosphates on IP3 come from?
2 from ATP and one for the original phosphatidic acid
Thank you Zenia