Lipid Synthesis and Transport

Question 1

How are carbohydrates and lipids stored?

Answer 1

Carbohydrates stored as glycogen

Lipids stored as triglycerols

Question 2

What is TAG synthesis?

Answer 2

Occurs when 3 fatty acids and glycerol phosphate from glycolysis combine with phosphate leaving the triglyceride

Question 3

What’s the first step in fatty acid synthesis?

Answer 3

Acetyl CoA -> Malonyl CoA

Question 4

What are lipoproteins?

Answer 4

They have an inner core of triglycerides and cholesterol and an outer shell of phospholipids, cholesterol and apoproteins
They’re lipid insoluble and transported as lipid protein complexes

Question 5

What are apoproteins?

Answer 5

They have a structural role

Question 6

Lipoproteins - what are chylomicrons?

Answer 6

Largest and lowest density

Carry mainly dietary TAG

Question 7

Lipoproteins - VLDL, LDL and HDL?

Answer 7

VLDL - carries mainly endogenous TAG
LDL - carries mainly cholesterol to the tissues
HDL - carries mainly cholesterol from the tissues to the liver

Question 8

What is the exogenous pathway?

Answer 8

Cholesterol and fatty acids absorbed
Triglycerides and cholesterol form chylomicrons
Chylomicrons enter circulation and travel to peripheral sites
Free fatty acids released from chylomicrons are used as energy or stored
Remnants form HDL

Question 9

What is the endogenous pathway?

Answer 9

VLDL hydrolysed to form remnants
Remnants incorporated into LDL
LDL taken to the liver and converted to bile salts and secreted to the intestines
In non-hepatic tissues LDL is used in hormone and membrane synthesis and taken up by macrophages

Question 10

Why are LDL receptors important?

Answer 10

They remove excess LDL from circulation so prevent high cholesterol levels

Question 11

The synthesis of cholesterol?

Answer 11

Acetyl CoA -> acetoacetyl CoA -> HMG-CoA -> Mevalonate -> cholesterol