Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
23 Cards in this Set
- Front
- Back
|
overall equation for cholesterol synth
|
18 ACoA, 18 NADPH, 18 ATP, 4 O2
cholesterol, 18 NADP, 18 ADP, 18 Pi, 9 CO2 |
|
|
solubility of cholesterol
|
most insol substance
.2 mg/dL yet plasma conc is similar to blood glucose |
|
|
structure of cholesterol
|
27 C's
4 rings hydroxy at 3 |
|
|
circulation of cholesterol
|
synthed in liver
circulate in lipoproteins -as chol esters -usually with linoleic acid |
|
|
cholesterol in membranes
|
100% in free (hydroxy) form
assoc w/sphingomyeline |
|
|
cholesterol in bile
|
disposal
mostly free cholesterol |
|
|
excretion of cholesterol
|
bile only
no enzyme to break rings can't excrete in urine or breath |
|
|
functions of cholesterol
|
membrane fluidity
-assoc w/sphingomyeline -form rafts -OH sticks out into interstit bile salts steroids |
|
|
location of cholesterol production
|
all cells (except RBC)
cytoplasm (mostly ER) especially liver adrenal, testes, ovaries also (pools of chol stored here) |
|
|
intermediates in cholesterol synth
|
isoprenoid's
ubiquinone (mito ETC) Dolichol (synth oligosacchs for GPs) Farnesyl & geranyl (anchor fctn in memb proteins) poss side effects for statins |
|
|
cholesterol in brain
|
not cross BBB
mostly in glials synthed in brain for brain use convert to 24 hydroxy & sent to liver |
|
|
24 hydroxylase
|
catabolic enzyme for cholesterol in liver
|
|
|
general rxn for Cholesterol synth
|
ACoA
HMG CoA (HMG CoA reductase is rate limit) mevalonic acid PPMV isoprenonyl (geranyl) (farnesyl) ... cholesterol 25-30 rxns |
|
|
first step cholesterol synth
|
move ACoA into cyto
via citrate |
|
|
production of HMG CoA
|
ACoA (after move into cyto)
thiolase & ACoA synthetase gives acetoacytal CoA(intermed) HMG CoA synthase (aka condensing enzyme- in mito will make ketone) generates HMG CoA |
|
|
fate of HMG CoA in cholesterol synthesis
|
gets reduced to mevalonic acid
HMG CoA reductase rate limiting step uses 2 NADPH |
|
|
fate of mevalonic acid
|
kinase generates PPMV
uses LOTS of ATP very high energy molecule |
|
|
generation of isoprene molecules in cholesterol synth
|
decarboxylate PPMV
|
|
|
generation of geranyl in cholesterol
|
isomerise & condense Isoprene
uses 2 isoprenes |
|
|
characteristics of geranyl
|
10C fatty acyl
high energy put on proteins increases hydrophobicity |
|
|
characteristics of farnesyl
|
from geranyl
(from isoprenes) changes protein characteristics |
|
|
bisphosphanates
|
tx osteoporosis & Ca
block production of farnesyl & geranyl inactivates GTPase decreases bone resorp SE: mandibular resorption (doesn't act in liver so no effect on chol) |
|
|
regulation of cholesterol synthesis
|
increased cholesterol:
-Plate HMG CoA reduct -inhib catalytic site -enhance proteolysis of HMGCoA -block translation HMG reductase -repress HMGCoA expression via SREBP low chol: -activate SREB -turns on transcription of reductase |
