cholestrol- triglycerides

Question 1

what is an essential component of cell membranes

Answer 1

cholesterol

Question 2

what does cholestrol form

Answer 2

bile and steroid hormones

Question 3

do we need to consume cholestrol

Answer 3

no bc ALL cells have the capability to synthesize it

Question 4

how can the origin of carbon atoms of cholesterol be deduced

Answer 4

from tracer experiments with acetate labelled in methyl carbon or carboxyl carbon

Question 5

what forms meavlonate

Answer 5

three acetates

Question 6

what does mevalonate form

Answer 6

phosphorylated 5C isoprene

Question 7

what forms the 30 c linear squalene

Answer 7

six isoprenes

Question 8

what forms cholesterol in the last step of synthesis

Answer 8

squalene cyclizes to form the four rings whic are modified to form cholesterol

Question 9

where is cholesterol formed

Answer 9

in the cytosol

Question 10

where are ketone bodies formed

Answer 10

in the mitochondria

Question 11

what is similar between cholesterol synthesis and ketone body synthesis

Answer 11

the enzymes and reactions

Question 12

where is acyl CoA derived from for ketone body formatino

Answer 12

B oxidation

Question 13

where is acetyl CoA derived from for cholesterol synthesis

Answer 13

from citrate

Question 14

what forms HMG CoA

Answer 14

three acetyl CoA are condensed

Question 15

what is reduced to form mevalonate

Answer 15

HMG CoA

Question 16

what is HMG CoA a target of

Answer 16

cholesterol lowering drugs

Question 17

another name for cholesterol lowering drugs

Answer 17

statins

Question 18

rate limiting step in cholesterol synthesis

Answer 18

HMG CoA reductase

Question 19

another name for thiolase

Answer 19

Acetyl CoA acetyl transferase

Question 20

where is NADPH dervied from for cholesterol synthesis

Answer 20

PPP

Question 21

step 2 of cholesterol synthesis

Answer 21

conversion of mevalonate to activated isoprenes

Question 22

how is mevalonate converted to activated isoprenes

Answer 22

3 phosphates are transferred stepwise from ATP to mevalonate
decarboxylation and hydrolysis creates a disphosphorylated 5 carbon product (isoprene) with a double bond
isomerization to a second isoprene

Question 23

what is step 3 of cholesterol synthesis

Answer 23

formation of squalene

Question 24

how is squalene formed

Answer 24

2 isoperenes join head to tail displacing one set of diphosphates forming 10 carbon geranyl pyrophosphate GPP

GPP joins to another isopentyl pyrophosphate to form 15C farnesyl pyrophosphate

two farnesyl pyrophosphates join head to head to form phosphate free squalene

Question 25

what are the 5 modes of regulation of cholesterol synthesis and trasnport

Answer 25

1. covalent modification of HMG CoA reductase 2. transcriptional regulation of HMG CoA gene 3. proteolytic degradation of HMG CoA reductase 4. activation of ACAT which increases esterification for storage 5. trasncriptional regulatino of LDL receptor

Question 26

how is HMG CoA regulated

Answer 26

at the gene expression level

Question 27

what does intracellular cholesterol concentration regulate

Answer 27

cholesterol synthesis

Question 28

what regulates intracellular cholesterol concentration

Answer 28

supply of ATP

Question 29

how is short term regulaition of activity of existing HMG CoA reducates regulated by

Answer 29

by phosphorylation by the AMP dependent protein kinase AMPK

Question 30

what stimulates phosphorylation of HMG CoA reductase

Answer 30

glucagon

Question 31

what promotes dephosphorylatino of HMG CoA reductase

Answer 31

insulin

Question 32

what inhibits HMG CoA reductase

Answer 32

statins

Question 33

what are the storage molecules for fatty acids

Answer 33

TAGS

Question 34

how are TGs carried in circulation

Answer 34

in lipoprotiens

Question 35

what is the TG structure

Answer 35

glycerol with 3 esterified FA

Question 36

what kind of reaction is addition of 3 FA to glycerol

Answer 36

dehydration where water is generation with the addition of each FA

Question 37

what needs to be done to FA before addition to glycerol

Answer 37

need to be activated by addition of CoA to carboxyl end like FA synthesis

Question 38

what is required for TG synthesis

Answer 38

-glycerol OR DHAP -NADH -activated FA -ATP -5 enzymes

Question 39

how is DHAP formed

Answer 39

glycolysis and glyconeogenesis

Question 40

what is the backbone for TG

Answer 40

glycerol 3 phosphate

Question 41

where do most glycerol 3 phosphates come from

Answer 41

DHAP from glycolysis or glyconeogeneis via glycerol 3 phosphate dehydrogenase

Question 42

what is the other way of making glycerol 3 phosphate

Answer 42

glycerol kinase which is the minor pathway in the liver and kidney

Question 43

synthesis of what occurs before TGs

Answer 43

phosphatidic acid

Question 44

what is the precursor of TG

Answer 44

phsophatidic acid

Question 45

what is phosphatidic acid made from

Answer 45

glycerol 3 phosphate

Question 46

what is phosphatidic acdi

Answer 46

uses glyecreol 3 phsophate backbone and the FA are attatched by acyl transferases and CoA is released

Question 47

what is the advantage of making phosphatidic acid

Answer 47

it can be made into Triacylglycerols or phospholipid

Question 48

what does phosphatidic acid phosphatase do

Answer 48

removes 3 phosphate from the phosphatidic acid yielding 1,2- diacylglycerol the third carbon is acylated with a third FA yielding TAG not by phosphatidic acid phosphatase