Chapter 24 (Cholesterol) Flashcards
Cholesterol is only generated by ___
animals
Cholesterol is weakly amphiphilic because of the lone ___
hydroxyl group
Cholesterol is a precursor to three things
steroids
bile salts
Vitamin D
A deficiency in Vitamin D can lead to:
Rickets
synthesized by sunlight
___ is the primary tissue for cholesterol synthesis
Liver (cytosol)
When we want to inhibit cholesterol synthesis we focus on the enzyme:
HMG-CoA Reductase (first committed step)
Done so by using Statins
Lovastatin
An inactive lactone that acts as an inhibitor to HMG-CoA Reductase
The lactone is hydrolyzed to mevinolinic acid, which is a competitive inhibitor or reductase
HMG-CoA Reductase is inactivated by
phosphorylation by cAMP-dependent kinases
Prenyltransferase is a ___ condensation reaction
head-to-tail
Synthesis of cholesterol from Squalene takes place here
endoplasmic reticulum membrane
LDL’s transport:
cholesterol to the tissues that need it
Why are LDL’s considered to be the “bad” type of cholesterol
because as they circulate they are subjected to oxidation
Too much oxidation leads to them not being able to bind to receptors
They become seen as foreign and turn into plaque
Chylomicrons
Produced by the intestinal mucosal cells
Has the lowest density
HDL’s role
Picks up excess cholesterol from the tissues and transports it back to the liver
All lipoproteins have this
hydrophobic interiors
When lipoproteins have a high TAG content this means they have: (trend)
low density
Which lipoprotein has the highest concentration of cholesterol esters
LDL’s
What determines the density of lipoproteins
protein content (higher content = higher density)
Extra cholesterol gets turned into:
bile salts
Chylomicrons get these when they bump into HDL’s
Apo C-II
LDL binding domain on ___
N-Terminus
Dysfunctions in or absence of LDL receptors lead to:
familial hypercholesterolemia
Which is worse: Hetero or Homozygous familial hypercholesterolemia
Homozygous
Requires a liver transplant since around 95% of LDL receptors are located on the liver
Excess cholesterol is converted into ___ acid and ___ inhibits this step
Cholic Acid (bile salt) Trans-fatty Acids
Low cholesterol levels will prevent 3 things
- absorption of cholesterol in SI
- liver synthesis of cholesterol
- absorption of bile salts in LI
Bile acids solubilize ___
ingested fats
