Lipid Cholesterol Metabolism Flashcards
Cholesterol is synthesized from what? Where?
Vehicles of Cholesterol Transport?
Name other types of organs that do Cholesterol synthesis?
What is needed for Cholesterol Synthesis (3)?
Acetyl-CoA is always produced in the?
Acetyl CoA; Liver (cytosol) Chylomicron, VLDL Remnants (high cholesterol) Adrenal Cortex, Sex organs ATP, NADPH (HMS) Acetyl-CoA Mitochondria
4 Functions of Cholesterol
Component of Membrane
Steroid/Bile Precursors
What is the rate limiting step of Cholesterol synthesis?
Reactants, Enzyme, Product
*this enzyme is heavily regulated
HMG-CoA + NADPH –> HMG Reductase –>
Mevalonate (C6)
Cholesterol Synthesis past Mevalonate (C6)? What did we need to know?
LOTS OF ATPPP
Mevalonate (C6) is decarboxylated –> C5 –> 6 of C5 merge forming Lanosterol (C30) –> modified (remove methyls and double bonds) –> Product = C27
What happens to intercellular Cholesterol (2)
How do we get rid of cholesterol? ***
Bile Salts/Acids **
Hormones
or can be esterified, and stored in lipid droplet temporarily)
How do liver cells react to over storage of Cholesterol (2): Im taking Cholesterol induced.
Down regulate LDL receptor synthesis (cholesterol accumulation causes –> change to cholesterol ester.
Inhibits LDL Receptor
Down regulate Cholesterol synthesis, through enzyme HMG -CoA reductase: Cholesterol accumulation causes enzyme to be phosphorylated (like glucagon does)
Name (2) ways by which HMG-CoA Reductase enzyme activity is reduced in the presence of Cholesterol? (details on #2)
1) Cholesterol Feedback Inhibition
2) Cholesterol Affects transcription on enzyme.
* **interferes w/activation, TF binding, and mRNA stability
Name and explain the two regulatory hormones?
Insulin (+) Gene expression and activity of enzyme
Glucagon (-) Gene expression and activity of enzyme
Drugs to Reduce Cholesterol Synthesis? (2)
Statins (Lipitor): Competitively binds to HMG-CoA Reductase –> less cholesterol syntesis
Bile secretion enhancers
Where in the liver cells are bile acids made?
Primary Bile Acids (C-Acids) vs Secondary (L/D - Acids)
Are both primary and secondary acids reabsorbed?
Where are secondary bile acids and salts absorbed?
Bile Acid vs Salts
Peroxisomes
Secondary - modified by intestinal bacteria
Yes
colon (Bacteria)
Bile acids have coo- group, in salts coo- is esterified
Give the reaction, enzyme (rate limiting) and allosteric inhibitor that is related to bile synthesis from cholesterol
Cholesterol –> Cholic Acid (bile)
Cholesterol 7 - alpha- hydroxylase
Cholic acid buildup down regulates enzyme.
Bile Acids help… (2)
ADEK absorption, activate pancreatic lipases