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How many carbons are in cholesterol
27
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How many rings of cholesterol
4
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Does cholesterol have a side chain
Yes, 8 carbons long
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What is the fuction of the hyrdoxyl on cholesterol
This is the form of cholesterol in membranes
Location for acylation
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What is the function of acylated cholesterol?
Storage form of cholesterol (with fatty acid chain)
Translocation of cholesterol in plasma lipoproteins
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Where is cholesterol made?
Liver, cytosol, with HMG coA reductase associated with the cytosolic side of the ER
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Describe the conversion of acetyl co A to mevalonate
Acetyl co A thiolase: add to acetyl co A, eliminate co Ash
HMG co A synthase: add acetyl group withanother acetl co A, eliminate coAsh
HMG co A reductase: eliminate acetyl co A and reduce C=O to form mevelonate. Uses 2 NADPH -->NADH
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Synthesis of cholesterol from mevolonate
6 carbon mevolonate --> 5carbon isoprenePP (uses 3 ATP and eliminates a CO2)
5 carbon isoprenePP X 3 =15 carbon farnesyl PPi
15 carbon farnesyl PPi X2 = 30 C Squaline
30 carbon squaline + OH plus cycle= Lanosterol
30 carbon lanosterol minus 3 CH3, reduce double bond, shift bond = 27 carbon cholesterol
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Regulation of HMG CoA reductase
- Increased activity by:
- dephos of enzyme by insulin
- Decreased by:
- phos of enzyme by glucagon
- high concentration of cholesterol
- inhibited by statins
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What are bile salts
Modified cholesterol to make more soluble in water, and to prevent aggregation of cholesterol
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Name 3 differences between cholesterol and cholate
- Cholate has:
- 5 carbon side chain instead of 8 C
- COO on side chain
- Hydroxylated on C7, C12
- Fully saturated rings
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Role of glycine and taurine
Amino groups added to side chain by amino bond. Makes more soluble in water
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Where are bile acids produced? Stored? Reabsorbed?
- Produced: liver cytosol
- Stored: gallbladder
- Reabsorbed: ilium and returned via hepatic portal vein
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Cholelithiasis
- Deficiency of bile acid production
- Gallstones
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Steatorrhea
Fatty feces from inability to produce enough bile to break down fat
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Steriods
Derived from cholesterol
have shortened side chain (usually about 27 carbons)
addition on carbonyl and hydroxyl groups, double bonds
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Vitamin D
Formed from modified cholesterol by UV radiation (photolysis)
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cholecalceferol
vitamin D
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calcitriol
activated vidamin d (in liver/kidney)
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