Apoprotein A-I activates LCAT Apoprotein C-I activates Lipoprotein lipase

Question 25

About Apoproteins the following are true except

a.       Apoprotein A-I activates LCAT

b.      Apoprotein C-I activates Lipoprotein lipase

c.       Apoprotein C-II inhibits Lipoprotein lipase

d.      Apoprotein C-III inhibits Lipoprotein lipase

Answer :

c.                   Apoprotein C-II inhibits Lipoprotein lipase

Reference :

Chaterjee 6th Edition Page 383

Quality :

Reader

QTDF :

Chaterjee

Discussion :

Liporproteins consists of a non polar core and a single surface layer of amphipathi phopsholipid and cholesterol molecules.

The protein moiety of a lipoprotein is known as an apolipoprotein or apoprotein, constituting nearly 70 % of some HDL and as little as 1 % of chylomicrons

Explanation

a.       Apoprotein A-I and A-II activates LCAT

b.      Apoprotein C-I activates Lipoprotein lipase

c.       Apoprotein C-II inhibits Lipoprotein lipase

d.      Apoprotein C-III inhibits Lipoprotein lipase

Comments

The chylomicrons are released by exocytosis from enterocytes into lacteals, lymphatic vessels originating in the villi of the small intestine, and are then secreted into the bloodstream, at the place where the lymphatic system falls into the blood stream, at the thoracic duct's connection with the left subclavian vein.

Tips

The following table has been adapted from Harper

Lipoprotein		Source	Diameter (nm)	Density (g/ml)	Composition		Main Lipid Components	Apolipoproteins
					Protein (%)	Lipids(%)
Chylomicrons		Intestine	90-1000	<0.95	1-2	98-99	Tricacylglycerol	A-I, A-II, A-IV, B-48, C-I, C-II, C-III, E
Chylomicron remnant		Chylomicrons	45-150	<1.006	6-8	92-94	Tricacylglycerol, Phospholipids, Cholesterol	B-48, E
VLDL		Liver (intestine)	30-90	0.95 – 1.006	7-10	90-93	Tricacylglycerol	B-100, C-I, C-II, C-III
IDL		VLDL	25-35	1.006 – 1.019	11	89	Tricacylglycerol, Cholesterol	B-100, E
LDL		VLDL	20-25	1.019 – 1.063	21	79	Cholesterol	B-100
HDL	HDL1	Liver, Intestine, VLDL, Chylomicrons	20-25	1.019 – 1.063	32	68	Phospholipids, Cholesterol	A-I, A-II, A-IV, C-I, C-II, C-III, D, E
	HDL2		10-20	1.063-1.125	33	67
	HDL3		5-10	1.125-1.210	57	43
	Preb HDL		<5	>1.210				A-I
Albumin/free faty acids				>1.281	99	1	Free fatty acids
HDL : High Density lipoproteins IDL : Intermediate Density lipoproteins LDL : Low Density lipoproteins VLDL : Very Low Density lipoproteins