Lipoprotein Metabolism

Question 0

How are triacylglycerol transported in the blood

Answer 0

Covered in previous lecture under fat metabolism

Question 1

How do you classify lipids in the blood?

Answer 1

• basic structure of a lipoprotein

- methods of measurement

Question 2

Synthesis of cholesterol by tissues

Answer 2

The precursors are cytoplasmic acetylCoA and NADPH. The pathways occurs mainly in the endoplasmic reticulum of virtually all Cells but is most active in the liver, small intestinal mucosa, other actively dividing cells plus in steroid producing tissues.

The main regulatory enzyme is HMGCoA reductase-it is highly regulated with a T1/2 of some 4 hrs. It is inhibited by XS membrane cholesterol at the level of gene transcription. Plus it is regulated covalently by insulin/glucagon ratio to be active I’m the FED state (ie dephosphorylated form)

Question 3

Transport of cholesterol in blood

For LDL and HDL

Answer 3

LDL- transport of preformed cholesterol TO the tissues (diagram)
HDL- transport of preformed cholesterol AWAY from the tissues (diagram)

Question 4

What is the role of the apoproteins in controlling lipoprotein metabolism

Answer 4

Apoproteins are proteins which are part of the structure of lipoproteins; they control the metabolism of lipoproteins- for example:
Chylomicron
-apoprotein C activates lipoprotein lipase
-apoprotein B48 directs the remnant to the liver

VLDL:

• apoprotein C activates lipoprotein lipase
• apoprotein B100 directs the remnant (LDL) to those tissues with an LDL receptor

Question 5

What are the interrelations between synthesis and exogenous supply of cholesterol

Answer 5

• cholesterol of under strong homeostasis in the body
• exogenous (dietary) cholesterol inhibits cholesterol biosynthesis
• too much tissue cholesterol I’m the membrane inhibits further uptake of exogenous cholesterol
• LDL and HDL also control cholesterol metabolism

Question 6

Look at pictures on pg 57

Answer 6

Do it