MB - Triglyceride Metabolism

Question 1

Describe the structure of Triglycerides

Answer 1

Three fatty acid chains ester-linked to a glycerol backbone

Question 2

Describe the structure of Fatty Acids

Answer 2

Long chain hydrocarbons
Can contain double bonds (Unsaturated)

Question 3

How can fatty acids be altered?

Answer 3

Elongases- Increase chain length by 2C
Desaturases- Add double bonds

Question 4

What are Essential FA’s? Why are Omega-3 and Omega-6 FA considered essential?

Answer 4

Fatty acids which cannot be produced by the body and so must come from the diet
- Humans don’t have the right desaturase to add double bonds lower than omega-9

Question 5

Why are FA’s altered? (4)

Answer 5

1. Fatty acid length –> Bilayer thickness
2. Degree of unsaturation –> Membrane Fluidity
3. Tissue-specific membrane composition
4. Specific FA act as precursors to signalling molecules

Question 6

Why do dietary lipids (e.g triglycerides) need to be digested?

Answer 6

Digestion by lipase allows the lipids to cross the plasma membrane into intestinal cells

Question 7

How are FA’s activated?

Answer 7

Using coenzyme A

Question 8

How are Triglycerides packaged?

Answer 8

Packaged into lipoproteins for transport in the blood to the tissues
- Must be packaged as they are too hydrophobic otherwise

Question 9

Describe the structure of a lipoproteins?

Answer 9

Formed from a mixture of lipid and protein
- Phospholipid and cholestrol outer layer
- Triglyceride and chol ester inner core

Question 10

How does the lipoprotein release fatty acids?

Answer 10

Endothelial cells on the adipose tissueare lined with the enzyme lipoprotein lipase
- Lipoprotein binds to the enzyme which cleaves off fatty acids- hence enter cells

Question 11

How are triglycerides sythesised in the adipose tissue?

Answer 11

1. G-3-P interacts with 3 activated FA’s
2. First 2 FA’s are added and then the phosphate on C3 is removed
3. Final FA is added to produce triglyceride