Exam 2: Cholesterol Flashcards
Cholesterol functions in modulating
Cell membrane fluidity
Highest concentration of cholesterol in
Plasma membranes
Cholesterol is precursor.to
Bile salts
Steroid hormone
Most cholesterol is ___ though the hydroxyl group to many LCFAs
Esterified
Enzyme that esterifies cholesterol
Acyl CoA cholesterol acyl transferase (ACAT)
Most human cells can make __
Cholesterol
___ is primary site of cholesterol synthesis
Liver
Other main locations that make cholesterol
Intestine
Adrenal cortex
Gonads
Cholesterol synthesis occurs in the
Cytosol
Some enzymes in cholesterol synthesis are bound to the
Endoplasmic reticulum
Reducing power in cholesterol synthesis comes from
NADPH
Energy in cholesterol synthesis comes from
Thioester cleavage
ATP
Carbon atoms in cholesterol synthesis comes from 3 things
- Oxidation of LCFA (OHOT)
- Oxidation of pyruvate (glycolysis)
- Oxidation of ketogenic AA
HMG-CoA goes to mevalonate via
HMG CoA reductase
Committed step in cholesterol synthesis
Mevalonate
4 basic steps in cholesterol synthesis
- Formation of mevalonate
- Formation of activated isoprenes (5C)
- Six isoprenes to form squalene (30C)
- Formation of cholesterol
Rate limiting enzyme in cholesterol synthesis
HMG CoA reductase
HMG CoA reductase is embedded in the
SER membrane
Regulation of HMG CoA reductase
- Insulin activates
- Glucagon deactivates
- Controls transcription of HMG CoA reductase protein
When HMG CoA reductase is phosphorylated by glucagon, it is
Deactivated
When HMG CoA is dephosphorylated by insulin, it is
Activated
Primary bile acids are make in the
Liver
Primary bile acids are secreted in the
Duodenum
Secondary bile acids are make in the
Intestine
