Lecture 24: Cholesterol

Question 1

cholesterol (“bile solids”)

Answer 1

-ubiquitous
-30% of human cell membrane
-precursor of BILE ACIDS and STEROID hormones

Question 1

Where can solid form cholesterol be found?

Answer 1

gallstones

Question 2

Cholesterol is the precursor of

Answer 2

-bile acids
-steroid horomones

Question 3

Atherosclerosis

Answer 3

-coronary artery disease and stroke
-caused by cholesterol

Question 4

Souurces of cholesterol

Answer 4

-diet: 200-300mg/day
-synthesis: 1g/day

Question 5

major producer of cholesterol

Answer 5

-liver

Question 6

Chemical properties of cholesterol

Answer 6

-amphipathic
-LOW solubility in water
-high concentration in plasma and bile

Question 7

Cholesterol transport

Answer 7

-by lipoproteins as a free form (30%) or cholesterol ester (70%)

Question 8

Cholesterol in bile is solubilized by

Answer 8

-bile acids
-phospholipids

Question 9

Synthesis of Cholesterol

Answer 9

-from ACETYL CoA in the CYTOSOL
-involves HMG-CoA synthase
-NO HMG-coA lyase activity

Question 10

Fates of HMG-CoA:

Answer 10

-mevalonate (reductase) (cystols)
-acetoacetate + acetyl-CoA (lyase)(mitochondria)

Question 11

HMG-CoA reductase

Answer 11

-HMG-CoA to MEVALONATE
-IRREVERSIBLE RATE-limitng step
-uses NADPH reducing cofactor

Question 12

HMG-CoA supressed by

Answer 12

-cholesterol
-statins

Question 13

Statins

Answer 13

-COMpetitive INhibtors of HMG-CoA reductase
-can lower plasma cholesterol up to 50%
-atorvastatin (lipitor)

Question 14

Cholesterol ester

Answer 14

-stored form of cholesterol in the liver

Question 15

Fates of cholesterol

Answer 15

-cholesterol ester in the liver
-sent out for membranes and steroid synthesis
-converted to bile acids

Question 16

bile acids

Answer 16

-AMPHIPATHIC
-secreted into bile
-stored in gall bladder
-secreted to small intestine
-EMULSIFYING agents for dietary fat

Question 17

Bile acids facilitate ___ to emulsify dietary fat

Answer 17

-hydrolysis by pancreatic lypase
-absorption of fat-soluble vitamins

Question 18

bile acid sequestrants

Answer 18

-cholestryamine and colestipol
-promote excrection of bile acids

Question 19

Regulation point of cholesterol synthesis

Question 20

Plasma lipoproteins

Answer 20

-protein/lipid complexes that for aggregates in plasma
-transport lipids from tissue to tissue and participate in lipid metabolism
-distinguished by their density differences

Question 21

Apolipoproteins

Answer 21

-each class of lipoprotein has characteristic composition
-serve as ligands for cell receptors

Question 22

Classes of lipoproteins

Answer 22

-HDL
-LDL
-IDL (intermediate)
-VLDL
-chylomicrons

Question 23

Lipoprotein structure

Answer 23

-INSOLUBLE core
-AMPHIPATHIC shell

Question 24

Chylomicron role

Answer 24

-transport lipid from INTESTINE to LIVER -or to becme glycerol and fatty acids (these go to peripheral tissues)

Question 25

VLDL role in lipid transport

Answer 25

-from liver to IDL -or gycerol + fatty acids

Question 26

IDL role in lipid transport

Answer 26

-send to LDL and back to liver -or glycerol and fatty acids

Question 27

LDL role in lipid transport

Answer 27

-send back to liver -send to peripheral tissues

Question 28

HDL role in lipid transport

Answer 28

-reverse cholesterol transport back to and from liver

Question 29

Familial hypercholesterolemia

Answer 29

-inherited -high LDL blood levels -no feedback inhibtion of cholesterol synthesis -premature arthreosclerosis and heart attacks -mutation of LDL receptor or apo B100

Question 30

Mutations causing hypercholesterolemia

Answer 30

-LDL receptor or apoB100 -little/no LDL receptor production -delivered to wrong place -bad binding -cannot be internalized