Lecture 15

Question 1

BETA OXIDATION’s four steps:

Answer 1

1. Oxidation.
   2. Hydration
   3. Oxidation
   4. Cleavage

Question 2

β-Oxidation: Step 1

Answer 2

○ step 1: oxidation of the α, single bond—> double bond (trans form)
○ Acyl-CoA dehydrogenase:
§ found on inner mitochondrial membrane.
§ not part of electron transport chain (ETC), but transfer e- flavoprotein to go to ETC
○ just like succinate —> fumarate of TCA
○ FADH2 produced.

Question 3

β-Oxidation: Step 2

Answer 3

○ Step 2: hydration of double bond in a trans fashion.
§ enoyl-CoA hydratase
§ just like fumarate —> malate of TCA

Question 4

β-Oxidation: step 3

Answer 4

○ step 3: oxidation of β hydroxyl to keto group.
○ 6-hydroxyacyl-CoA dehydrogenase
○ just like malate —> oxaloacetate of TCA
○ NADH produced.

Question 5

β-Oxidation: step 4

Answer 5

○ step 4: cleavage by thiolysis (reverse Claisen condensation)
§ thiolase (acyl-CoA acetyltransferase)
□ ping pong mechanism
§ Acetyl-CoA produced
§ Carbon chain now 2-C shorter, but has new acyl-CoA ready for next round.

Question 6

Energy from β-Oxidation

Answer 6

§ 8 acetyl CoA produced
			§ 7 rounds of β oxidation 
				○ 7 FADH2
				○ 7 NADH
			§ 8 Acetyl-CoA goes to TCA cycle
				○ 24 NADH  (3)
				○ 8 FADH2  (1)
				○ 8 GTP  (1)
			§ All NADH and FADH2 go to electron transport chain.

Question 7

Oxidation of unsaturated fatty acids:

Answer 7

○ Need 2 more enzymes:
§ isomerase: converts cis double bonds to trans at C-3 (the β carbon)
§ Reductase: reduces cis double bonds not at C-3
○ Monounsaturated FAs (1 double bond)
§ Need isomerase only
§ Overall, just 1 fewer FADH2 made (1st step skipped)
§ PUFAs with odd number of double bonds also do this.
○ PUFAs (multiple double bonds)
§ Need both enzymes
§ 1 fewer FADH2 and 1 fewer NADH made.