Cholesterol Synthesis Flashcards
Cholesterol is a precursor to:
Bile acids, steroid hormones, Vitamin D
What is the naming convention of steroid molecules?
End in -ol or -one
Name 3 steroid molecules/hormones
Cortisol, testosterone, estradiol
Name 2 disorders caused by excess cholesterol
Cardiovascular disease and gall stones
What is the test used to diagnose problems in the gall bladder?
Cholecystogram
Blood levels of cholesterol are due to what two sources?
50% diet
50% synthesized in body’s cells
List the three locations of DeNovo synthesis of cholesterol
Liver, adrenals, gonads
How many total carbons are in the cholesterol molecule?
27 carbons
List the steps for cholesterol synthesis in order
acetyl CoA -> HMG CoA -> mevalonate -> farnesyl pyrophosphate -> squalene -> lanosterol -> cholesterol
What is the end product of Stage 1?
Mevalonate
What are the enzymes used in Stage 1?
HMG CoA reductase and HMG CoA synthase
What is the allosteric enzyme in Stage 1? What coenzyme is needed?
HMG CoA reductase
NADPH+
What hormone increases cholesterol synthesis?
Insulin
Name three things that down-regulate cholesterol synthesis
Cholesterol, glucagon, and statin drugs
What is the end product of Stage 2?
Farnesyl pyrophosphate
What coenzymes are needed for Stage 2?
ATP and Mg2+
The end product of Stage 2, farnesyl pyrophosphate, is an important intermediate in the synthesis of what other molecule?
CoQ10 aka ubiquinone
In the absence of CoQ10, what is the dose needed to replete the drug induced nutrient deficiency?
100mg
What is the end product of Stage 3?
Squalene
What is squalene capable of being?
Capable of being a ring, but it is not
What is the enzyme used in Stage 3?
Squalene synthase
What is the location of the enzyme squalene synthase?
Endoplasmic reticulum
What are the coenzymes for squalene synthase?
NADPH+, Mg2+, Mn2+
What is the end product of Stage 4?
Lanosterol
What is the enzyme for Stage 4?
Cyclase
What is the coenzyme for Stage 4?
NADPH+
What is the final product of cholesterol synthesis?
Cholesterol
What coenzyme is needed for Stage 5?
NADPH+
Name the 7 factors/lifestyle that increase cholesterol synthesis
- high blood pressure
- smoking
- male gender
- abdominal obesity
- lack of exercise
- drinking soft vs hard water
- elevated serum free fatty acids
What is the largest product that cholesterol is used for?
Bile salts/acids
What enzyme is required for synthesis of bile acids?
7 alpha hydroxylase
What are the coenzymes for 7 alpha hydroxylase?
NADPH+ and Vitamin C
What vitamin can be used in high doses to decrease blood cholesterol levels?
Niacin (vitamin B3)
What is the name of the hormone that increases the synthesis of bile?
Hepatocrinin
What causes hepatocrinin to be released?
Fat in the duodenum
What is the name of the hormone that causes the gall bladder to contract?
Cholecystokinin
Without fiber, how much bile is reabsorbed into the portal system and resecreted?
98%
Can cholesterol be digested or metabolized?
No, it cannot enter Krebs cycle
How much cholesterol is excreted in the feces?
1 gram
What do bacteria convert cholesterol to in the colon?
Coprostanol
What color is coprostanol?
Blue
What is steatorrhea?
Foul smelling floating stool
Guinea pigs can get atherosclerosis if they are deficient in which Vitamin?
Vitamin C
Natural dietary advice used to decrease blood LDL levels includes what two things?
Vitamin C and bran (especially oat bran)
