Biochemistry week 3 Flashcards
What is the function of cholesterol
- Structural component for all cell membranes
What is cholestorl a percursor for?
- Bile acids
-Steroid hormones
-Vitamin D
Early cholesterol synthesis provides substrates important for what
- Cell proliferation
-Electron transport–Combating oxidative stress
What regulates cholesterol homeostasis
- The liver
What does plasma cholestrol depend on
- Endogenous ( body made) synthesis
-Dietary intake
Explain the structure of cholesterol
- Very hydrophobic
-Contains 4 fused hyrocarbon rings called steriod nucles
-
What does Ring A on cholesterol have
- Hydroxyl group at carbon 3
What does Ring B on cholesterol have
-Has double boned between C5 and C6
Where can cholesterol be synthesized
- Liver
-Adrenal cortex
-Intestine
-Reproductive organs
In cholestorl synthesis where do all the carbon atoms come from
acetyl coA`
What provides the reducing power in cholesterol synthesis
- NADPH
Where are the enzymes involved in cholesterol synthesis located in
- Cytosol
-SER
-Perioxisome
To make 1 mol of cholestrol how much acetylcoA, ATP ans NADPH is used
- 18 moles of acetyl CoA
-36 moles of ATP
-16 moles of NADPH
Name what regulates cholesterol synthesis
-Sterol-dependent regulation of gene expression
-Sterol independent phosphorylation/dephosphorylation
-Drug inhibition
-Hormonal regulation
Name the proteins involed in Sterol-dependent regulation of gene expression
SREBP2
-SCAP
Explain what happens in sterol-dependent regulation when cholesterol levels are LOW
- SREBP2, moves from ER to the golgi
-Proteolysis activates SREBP
-Then the active SREBP2 enters the nucles and promotes gene transcription for cholesterol synthesis
Explain what happens in sterol-dependent regulation when cholesterol levels are HIGH
- Cholesterol binds to SCAP, causing a conformational change
-SCAP binds to insig-1 -SREBP remains inactive so gene transcription is repressed
