8. lipoprotein metabolism

Question 1

Answer 1

Question 2

what inhibits HMG CoA reductase?

Answer 2

statins

Question 3

1 molecule of cholesterol requires:

Answer 3

18 molecules AcCoA

36 ATP

16 NADPH (NADH with phosphate group) used in biosynthetic reactions

Question 4

what is cholesterol a precursor to?

Answer 4

–Bile acids

–Steroid hormones

–Vitamin D

Question 5

what are lipoproteins composed of?

what is their function?

Answer 5

lipid and apoprotein

carries lipids aroundthe body via blood plasma

•Carried from sites where they are synthesized or abundant to where they are used, stored or secreted

Question 6

Answer 6

phospholipid monolayer

free cholesterol outer

central core hydrophobic lipids and cholestryl ester (esterified form OH group on LCFA even more hydrophobic)

Question 7

what are the different types of lipoproteins?

Answer 7

Question 8

what is an apoprotein?

what are the functions of apoproteins?

Answer 8

proteins associated with lipoproteins

–Interact with cellular receptors

–Activate and inhibit enzymes involved in lipoprotein metabolism

Question 9

what are the major apoproteins?

Answer 9

A: AI, II, IV -> HDL

B: B48, B100 -> LDL receptor

C: I,II, (activates lipoprotein lipase) III (inhibits LPL lipase

E: E2 (isoform CHD), E3, E4 (isoform of alzhemeirs) receptor recognition

Question 10

Answer 10

Question 11

Answer 11

Question 12

what are chylomicrons?

Answer 12

TGs mixed with cholesterol, phospholipids and apoprotein (B48)

Question 13

how do chylomicrons reach plasma?

what do they acquire?

and then where are they transported?

Answer 13

via thoracic duct after secreted into lymph

apoC-II and apoE from HDL

adipose/muscle

Question 14

Answer 14

Question 15

Apo CII

Answer 15

•Activates lipoprotein lipase (LPL)

TGs —> FFA + glycerol

•LPL found on the surface of endothelial cells of capillaries

Question 16

Answer 16

Question 17

what do VLDL contain?

Answer 17

•Contain TG, cholesterol, CE, apoB-100, apoC-II and apoE

Question 18

what do IDL have

what are the two fates of IDL

Answer 18

dont have apo CII

richer in cholesterol as it has lost its TG

–liver and be destroyed(60%)

–lose more TG and become LDL (40%) (cholesterol, CE and apoB-100)

Question 19

LDL

Answer 19

• Contains apoB-100, CE, cholesterol
• LDL is the major cholesterol carrier for delivery to tissues.
• High levels of LDL (> 5.2mmol/L) associated with CHD
• Desirable level < 4.1 mmol/L

Question 20

HDL

Answer 20

• Transports cholesterol from peripheral tissue to liver – reverse cholesterol transport (RCT)
• Circulating store of apoprotein
• “Good” cholesterol. 1.4 mmol/L protect against CHD.

Question 21

Answer 21

Question 22

LCAT

Answer 22

lecithin:cholesterol acyl transferase

esterifies cholesterol to form cholesterol esters

activated by apoA-1

Question 23

what is needed for re beta HDL to be transported to peripheral tissue/ macrophages?

Answer 23

ABCA1 transporter, SRB1

Question 24

CETP

Answer 24

Cholesterol ester transfer protein

Transfers cholesterol esters from HDL to particles e.g.VLDL