Cholesterol Flashcards
This substance is an essential component of cell membranes and is a precursor to bile salts and steroid hormones.
Cholesterol
Only about 30% of circulating cholesterol occurs in the free form. Most are what?
Esterified long chain fatty acids attached to hydroxyl groups
This type of cholesterol is more hydrophobic, not located in membranes, transported by lipoproteins, and solubized in bile.
Esterified cholesterol
What is the primary site of cholesterol production?
Liver, primarily in the cytosol
What are raw materials needed for cholesterol synthesis?
ACETYL CoA -Oxidation of long-chain fatty acids (OHOT) -Oxidation of pyruvate (glycolysis) -Oxidation of ketogenic amino acids NADPH and ATP
What is the rate limiting, key regulatory step of cholesterol synthesis?
HMG CoA reductase
What does HMG CoA reductase create?
Mevalonate, which is the first unique compound in cholesterol synthesis
When is HMG CoA reductase active? Inactive?
- Active when non-phosphorylated
- Inactive when phosphorylated
Where are bile acids/salts primarily made?
- In the liver and secreted into the duodenum
- Can also be made in the intestines
In simple terms, what is the process of cholesterol synthesis?
- Eat carbohydrate
- Muscle and liver are full of energy and glycogen
- Glucokinase pushes glycolysis forward (liver)
- Prep step runs
- Start the Kreb’s cycle
- Citrate is kicked out (high energy charge)
- Citrate lyase gives back the acetyl CoA
- Make fat and cholesterol
Is there degradation of cholesterol?
No
What is cholesterol synthesis stimulated by?
ATP, NADH, Insulin, and Fructose
What is cholesterol synthesis inhibited by?
ADP, AMP, NAD+, and glucagon
These are competitive inhibitors of HMG CoA reductase.
Statins
Which hormones upregulate HMG CoA reductase? Downregulate?
- Insulin and thyroxine upregulate
- Glucagon and glucocorticoids downregulate
