Flashcards in Quiz 3 Cholesterol Synthesis Deck (31)
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1
Nearly all tissues can synthesize cholesterol from what?
Acetyl CoA
2
20% of cholesterol synthesis happens where?
In the liver
3
Extrahepatic sites cholesterol can be synthesized?
Intestine, adrenal cortex, reproductive tissues
4
Chylomicron remnants go to where and converted to bile salts?
liver
5
Free cholesterol is an essential component of what?
cell membranes (this regulates the fluidty, gives strength to the membrane)
6
Free cholesterol is precursor to?
bile salts and steroid hormones
7
Type of cholesterol not located in membranes and is MORE hydrophobic?
esterfied cholesterol
8
What are two outcomes of excess cholesterol?
Gallstones and Atherosclerosis (cholesterol deposited at the linings of blood vessels)
9
30% of circulating cholesterol is this form?
Free cholesterol
10
Cholesterol Synthesis occurs where in the cell?
Cytosol
11
Reducing power of cholesterol synthesis?
NADPH
12
What things are required in cholesterol synthesis?
ATP, molecular O2, Acetyl CoA
13
What are the 3 stages of cholesterol synthesis?
Stage 1: 3 Acetyl CoA → HMG-COA
Stage 2: HMG-CoA → Mevalonic Acid (mevalonate) → Squalene
Stage 3: Squalene → Cholesterol
14
What is the rate-limiting, key regulatory step of cholesterol synthesis?
HMG-CoA reductase (remember this occurs in the cytosol)
15
Product of HMG-CoA Reductase?
Mevalonate (mevalonic acid)
16
Is HMG CoA reductase reversible or irreversible?
IRREVERSIBLE
17
As cholesterol concentration increases, what does this do to HMG CoA reductase?
Inhibits it (low cholesterol levels stimulate this enzyme)
18
HMG CoA reductase is active or inactive (inhibited) when phosphorylated by AMP-activated protein kinase?
Inhibited when phosphorylated (stimulated when non-phosphorylated)
19
Competitive inhibitors of HMG CoA reductase which block endogenous synthesis of cholesterol?
Statins
20
What type of bile salts are made in the liver and then secreted into the duodenum?
Primary bile salts
21
Which type of bile salts are made in the intestine?
Secondary bile salts
22
All bile salts end in?
Cholic acid or cholate
23
Difference in polar and non polar bile salts?
Number and position of hydroxyl groups
24
What is the precursor for all steroid hormones?
Pregnenolone
25
Cholesterol synthesis an energy requiring pathway?
YES!! Lots of energy required
26
What are the ingredients again for Cholesterol synthesis?
Acetyl CoA, NADPH. O2, and ATP
27
What is the first unique compound in cholesterol synthesis?
Mevalonate
28
Cholesterol is a precursor for?
Bile Salts and steroid hormones
29
Can cholesterol be degregaded? If not how is it excreted?
No, excreted in bile
30
Glucose, fructose, insulin, thyroxine stimulate or inhibit cholesterol synthesis?
Stimulate
31
