Week 12 - Unit 3 Flashcards
Cholesterol can come from both the diet and is synthesized in the body. True or false?
True
True or False:
the majority of cholesterol in the body is form dietary sources.
False- most is from endogenous synthesis
Cholesterol is used as a membrane sterol and is the precursor for all ______ ______.
Steroid hormones
Cholesterol is transported in ______ in the body.
Lipoproteins
Dietary cholesterol is transported in ______.
chylomicrons
Cholesterol is synthesized in the _____ (but most tissues can synthesis it if needed) and packaged into _____ particles.
Liver (primary)
VLDL
VLDL particles mature to ______ particles, that are taken up by cells via the ____ ______.
LDL
LDL receptor
Cholesterol is transported from peripheral tissues back to the liver via _____ particles.
HDL
What three levels is cholesterol synthesis regulated at ?
Phosphorylation
Transcription
Feed-back inhibition
Statins are cholesterol reducing drugs that target the regulatory enzyme ______.
HMG CoA reductase
Cholesterol has a ring structure with a _____ group on the ___ carbon, this allows it to be amphipathic (can insert into membrane).
Hydroxyl
3 carbon
Cholesterol is a ______ (shape)molecule and can influence the _____ of the cell membrane when inserted.
planar
fluidity
Approx how much cholesterol in the body is in the free form ?
1/3
What happens to the other 2/3 of the cholesterol in the body that is not in free form?
It is Esterified
-FA added with ester bond to the OH on the 3 carbon of Cholesterol
What does esterification of cholesterol do ?
keeps the cholesterol within the cell and out of the cell membrane (means of storage)
Creation of Cholesterol needs a lot of energy and is provided in the form of _____.
NADPH
Synthesis of Cholesterol starts with condensation of 2 _____ to make ______.
Acetyl CoA (CoAsh is released)
Acetoacetyl CoA
What is the intermediate generated in the first steps of cholesterol synthesis?
Mevalonate
In synthesis of Cholesterol, what does Acetoacetyl CoA condense combine with to make beta-hydroxy-beta-methyl glutaryl CoA (HMG-CoA)
Acetyl CoA (CoASH is released)
Where does Cholesterol synthesis take place?
Where does ketone synthesis take place?
Cytosol
Mitochondria
What is the regulatory enzyme for Cholesterol synthesis in the first steps involving Acetyl CoA to form intermediate Mevalonate?
HMG-CoA reductase
Where is HMG-CoA reductase?
describe its physical features?
ER membrane
8 Transmembrane domains
What does HMG-CoA reductase in the ER membrane use for energy?
2NADPH+2H
and release of CoASh
What level is HMG-CoA reductase regulated at ?
Transcriptional level (highly regulated)