Lipoprotein physiology

Question 1

1. List the relative polarities of cholesterol ester, triglyceride, unesterified cholesterol and phospholipids.

Answer 1

Phospholipids>cholesterol ester> cholesterol>triglycerides

Question 2

2. Describe the characteristics of the five classes of lipoproteins.

Answer 2

Chylomicron- 10:1 triglyceride to cholesterol ester

• dietary fat pathway
• APO-B48 stuctural lipoprotein
• Apo-C2- cofactor for lipoprotein lipase
• Apo E- remnant receptor allows IDL to be cleared

IDL- 1:1 triglyceride to cholesterol ester

• APO B-48 or B100
• APO C2
• APO E

VLDL- 5:1 triglyceride to cholesterol ester

• APO- B100 structural scaffold
• APO- C2 cofactor for lipoprotein lipase
• APO E- remanant receptor

LDL- 65% cholesterol ester

• Apo B100 interacts with LDL receptor in the liver and is taken up (associated with familial hypercholesterolemia
• APO E remant receptor

HDL- almost all cholesterol ester

• APO A1- structural
• acts as a trash truck

Question 3

3. Describe the fate of the five classes of lipoproteins in the chylomicron, VLDL and HDL pathways.

Answer 3

chylomicron takes TAG’s from enterocyte through lymphatics to the thoracic duct in the blood it interacts with lipoprotein lipase through C2 receptor to drop off FA’s into cell. then is considered an IDL and heads back to liver through APOE to be recycled

VLDL- synthesized in the liver heads out to tissue interacts with Lipo protein lipase to drop off tags and then becomes LDL, cleared through APO B by liver

HDL heads out ijnto blood picks up cholesterol through ABC-A1 (associated with tangeres disease), LCAT makes cholesrol, cholesterol ester and then HDL trades Chlesterol ester for TAGS from chylos or VLDL through cholesterol ester transfer protein, and then heads back to liver.

Question 4

5. Describe the functions of CETP, ABCa1 and LCAT.

Answer 4

seen above