Lipid Biochemistry I

Question 1

triglyceride and cholesterol transport in blood

Answer 1

as lipoproteins

Question 2

lipoproteins - least to most dense

Answer 2

chylomicrons
VLDL
IDL
LDL
HDL

Question 3

chylomicrons

Answer 3

transport dietary triglyceride and cholesterol
apo B-48
apo C-II
apo E

Question 4

VLDL

Answer 4

transport triglyceride from liver to tissues

apo B100
apo C-II
apo E

Question 5

IDL

Answer 5

VLDL remnant

apo E
apo B100

picks up cholesterol from HDL to become LDL

Question 6

LDL

Answer 6

delivers cholesterol into cell

apo B100

Question 7

LDL receptor

Answer 7

binds to apo B100

Question 8

HDL

Answer 8

picks up cholesterol in blood vessels
-delivers to liver

also shuttles apo C-II and apo E

activates LCAT - produce cholesterol esters

Question 9

apo B48

Answer 9

on chylomicrons

-required for release from epithelial cells into lymphatics

Question 10

apo B100

Answer 10

on VLDL

-mediates release into blood from liver

Question 11

chylomicrons and VLDL

Answer 11

transfer triglycerides to adipose and muscle tissue

chylomicron - from diet
VLDL - from liver

Question 12

lipoprotein lipase

Answer 12

required for metabolism of chylomicrons and VLDL

-activated by apo CII

Question 13

chylomicron course

Answer 13

from dietary triglycerides

• apo B48 for release from epithelial cells to lymphatics
• leave lymph - enter blood - pick up apo CII and apo E from HDL
• in adipose and muscle tissue - apo CII activates lipoprotein lipase - release triglycerides
• remnant picked up by liver via apo E

Question 14

VLDL course

Answer 14

synthesized in liver

• apo B100 to release to blood
• acquire apo CII and apoE from HDL
• metabolized by lipoprotein lipase

remnants - IDL

• some picked up by liver (apoE)
• rest remain in blood - further metabolism
• acquire cholesterol esters - become LDL

Question 15

LDL

Answer 15

primarily cholesterol ester

• role - deliver cholesterol to tissues for biosynthesis
• ex/ steroids, bile acids and salts

80% picked up by liver

only have apo B100
-mediates endocytosis

Question 16

SR-B1 receptor

Answer 16

transfer of cholesterol from HDL to liver

Question 17

ACAT

Answer 17

enzyme for storage of cholesterol esters

Question 18

HMG-CoA reductase

Answer 18

de novo synthesis of acetyl CoA

Question 19

LDL receptor

Answer 19

for apoB100

Question 20

HDL

Answer 20

synthesized in liver and intestines

• dense protein rich particles in blood
• apo A1 for cholesterol recovery from fatty streaks in blood vessels

carry apoE and apoCII
-donated to chylomicrons and VLDL

Question 21

LCAT

Answer 21

lechitin cholesterol acyltransferase

• activated by apo A1 on HDL
• adds fatty acid to cholesterol - producing cholesterol esters
• dissolve in core of HDL
• allow transport of cholesterol from periphery to liver

Question 22

CETP

Answer 22

cholesterol ester transfer protein

-facilitates transfer of cholesterol esters picked up in periphery to IDL - resulting in LDL

Question 23

SR-B1

Answer 23

scavenger receptor
-HDL cholesterol picked up in periphery can also enter cells

-in hepatocytes, steriodogenic tissues

not endocytosis of HDL - but transfer of cholesterol into cell
-unknown mechanism

Question 24

type I hypertriglyceridemia

Answer 24

mutated lipoprotein lipase
-excess triglyceride in blood and deposition in tissues

orange-red eruptive xanthomas - mucous membranes and skin

abdominal pain, acute pancreatitis

milk turbididty of serum plasma

elevated chylomicrons in blood

Question 25

type IIa hypercholesterolemia

Answer 25

deficient LDL receptor -dominant genetic disease elevated LDL cholesterol -increased atherosclerosis risk and CAD - xanthomas of achilles - subQ tuberous xanthomas over elbows - xanthelasma - lipid in eyelid - corneal arcus

Question 26

abetalipoproteinemia

Answer 26

a hypolipidemia -low apoB100 and apoB48 - serum triglycerides low - cholesterol low fat accumulation in intestinal enterocytes and in hepatocytes essential FAs and vit A and E are not well absorbed steatorrhea, cerebellar ataxia, pigment retina degeneration, acanthocytes, loss of night vision

Question 27

cholesterol metabolism

Answer 27

required for membrane, steroid, and bile acid synthesis most cell sget from LDL or HDL some synthesized de novo -most in liver - from acetyl CoA

Question 28

cholesterol synthesis pathway

Answer 28

``` acetyl CoA > acetoacetyl CoA > HMG CoA > mevalonate > farnesyl PP > squalene > lanosterol > cholesterol > steroids, vit D, bile acids ```

Question 29

HMG CoA reductase

Answer 29

inhibited by statins stimulated by insulin converstion of HMG-CoA to mevalonate - step in synthesis of cholesterol

Question 30

farnesyl pyrophosphate

Answer 30

intermediate in cholesterol pathway - can be used in synthesis of CoQ for ETC - snythesis of dolichol pyrophosphate - N-linked glycosylation of proteins in ER