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19 Cards in this Set
- Front
- Back
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Cholesterol is the primary precursor for what compounds?
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Bile acids/salts, vitamin D, corticosteroids, and sex hormones.
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Less than ___ of the cholesterol in the body comes from diet?
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1/3
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Cholesterol is made by what kind of cells?
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Nearly every nucleated cell.
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What is the major way the body gets rid of cholesterol?
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Through the feces.
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Where do all the carbons for cholesterol come from?
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Acetyl-CoA
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Where do the reactions of cholesterol biosynthysis take place?
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In the cytosol.
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How many stages are there is the reactions?
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There are five stages, each with a series of reactions.
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What is the most important stage of cholesterol biosynthesis?
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The first stage, is the rate limiting step.
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What is the enzyme used in the first reaction?
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2 Acetyl-CoA ===> Acetoacetyl-CoA + CoA. The enzyme used in thiolase.
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What is the rate limiting reaction of the cholesterol biosynthesis?
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The third reaction of the the first stage is the rate limiting step.
HMG-CoA+2HADPH+2H---> Mevalonate +2NADP +CoASH |
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What is the rate limiting steps enzyme?
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HMG-CoA reductase.
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How do statins work?
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They reversibly inhibit the rate limiting reaction of the biosynthesis, stopping the production of Mevalonate.
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What is an interesting result of taking statins?
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It triggers the increase of LDL receptors on all cell membranes. This imediately acts to grab up all the available LDL, bringing the LDL cholesterol even lower.
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How id cholesterol synthesis regulated by genetic controll?
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The HMGR gene has a sterol regulating element. Sterols inhibit the transcription of HMGR mRNA synthesis.
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What do excess levels of Mevalonat do to the reaction?
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It inhibits the transcription of HMGR mRNA.
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Can reactants be removed from the process?
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Yes Geranyl Pyrophosphate an Farnesyl pyrophosphate can leave and undergo other reactions.
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What do bile salts do?
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They are released by the gall bladder to help solubilize dietary fats.
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What do colestipol or cholestyramine do?
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They are non-digestible polymers that bind to dietary fats after they are combined with bile salts. This prevents the reuptake of the cholesterol by the hepatic portal system, an allows it to be passed through the bowels.
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What are the main sources of dietary cholesterol?
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Beef liver/kidney, egg. Meat.
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