Met 1: Fatty Acid Synthesis

Question 1

Fatty acid synthesis

• Starting substrate
• End product
• Location

Answer 1

Fatty acid synthesis

• Starts with pyruvate
• Ends with palmitate
• Occurs in cytoplasm (once citrate leaves mitochondria)

Question 2

When do we make glucose?

When do we make fats?

Answer 2

We make glucose when we don’t have enough fuel.

We make fats when we have too much fuel!

Question 3

What are three purposes for fatty acid synthesis?

Answer 3

1. Energy storage
2. Signaling molecule production
3. Membrane & structural molecule production

Question 4

Can fats be made from carbohydrates? AA’s?

Answer 4

Fats can be made from both AA’s and carbohydrates!

Question 5

What are the essential fatty acids and why are they essential?

Answer 5

Linoleic acid and Linolenic acid (omega 6, omega 3) are essential b/c we cannot create double bonds past C9

Question 6

Why do alcoholics get fatty liver or elevated lipids?

Answer 6

etOH -> acetate -> acetyl-coA -> fatty acids!

Ethanol can be converted to fatty acids when we have excess calories

Question 7

Describe the basic process of lipid synthesis

(intermediates, enzymes, location)

Answer 7

1. Citrate starts in the mitochondria (part of TCA cycle)
2. Citrate is moved into cytoplasm
3. Citrate is converted to acetylcoA
4. Acetyl-coA is converted to malonyl coA
   
   • By acetyl-coA carboxylase
5. Malonyl coA is converted into palmitoyl coA
   
   • by fatty acid synthase

Question 8

Does fatty acid synthesis create or expend energy?

Answer 8

Fatty acid synthesis stores energy to be used for later, but it requires SPENDING energy to do so.

*ATP, NADH required for fatty acid synthesis

Question 9

Describe the effect of insulin and glucagon on lipid synthesis/breakdown

Answer 9

Insulin promotes lipid synthesis

Glucagon promotes lipid breakdown

Question 10

What is the rate limiting step of fatty acid synthesis?

What are the inputs?

Answer 10

Conversion of acetyl-coA into malonyl-coA by acetylcoA carboxylase.

This requires CO2 and ATP

Question 11

Describe the regulation of acetylcoA carboxylase by

• Insulin/glucagon
• Citrate

Answer 11

• Insulin and glucagon
  
  • dephosphorylation by insulin ACTIVATES acetylcoA carboxylase
  • glucagon inhibits acetylcoA carboxylase
• Citrate
  
  • induces polymerization (and activation) of acetyl-coA carboxylase

Question 12

Describe the function of fatty acid synthase

What are its 3 inputs?

Answer 12

Fatty acid synthase creates fatty acids by adding 2C at a time to a growing chain

Inputs: malonyl coA, existing fatty acid chain, NADPH

Question 13

What are two possible fates for palmitoyl coA?

What enzymes carry out each?

Answer 13

1. Elongation by fatty acid elongase
2. Desaturation by mixed function oxidase

Question 14

Describe the activation of glycerol and free fatty acids prior to triglyceride formation

Answer 14

• Glycerol -> glycerol phosphate
  
  • in liver and adipose tissue
• Free fatty acids -> fatty acid coA
  
  • by fatty acyl-coA synthetase

Question 15

Describe the creation of triglycerides from activated precursors. Where do TG’s go next?

Answer 15

• Fatty acid acyl-coA units are added one at a time to glycerol phosphate.
• TG then goes into storage (liver) or transport (lipoprotein)