Chapter 18, Problem 18.73UTC

Interpretation Introduction

To determine:

a. Number of cycles of ß-oxidation for complete oxidation of lauric acid.

b. Number of acetyl CoA produced for complete oxidation of lauric acid.

c. Total ATP yield for complete ß-oxidation of lauric acid.

Answer to Problem 18.73UTC

Solution:

a. Five (5) cycles of ß-oxidation are needed for the complete oxidation of lauric acid.

b. Six (6) acetyl CoA are produced from the complete oxidation of lauric acid.

c. 78 ATP yields from the complete oxidation of lauric acid.

Explanation of Solution

Lauric Acid is a C₁₂ fatty acid and for the activation of lauric acid 2 ATP are required.

The acetyl group of the acetyl CoA is formed by two carbons. And in the last round two acetyl CoA are produced. Accordingly, the number of cycles of ß-oxidation and the number of acetyl CoA produced has been calculated.

From the complete ß-oxidation of lauric acid, total six (6) acetyl CoA, 5 NADH and 6 FADH₂ has been produced. Each Acetyl CoA yields 10 ATP, each NADH yields 2.5 ATP and each FADH₂ yields 1.5 ATP. Accordingly, ATP yield has been calculated.

Formula used: Number of cycles of ß-oxidation needed for the complete oxidation of fatty acid = $\frac{\text{n}}{\text{2}}\text{-1}$

Where n = Number of carbon atoms present in fatty acid.

Number of acetyl CoA produced from the complete oxidation of fatty acid = $\frac{\text{n}}{\text{2}}$

Where n = Number of carbon atoms present in fatty acid.

Calculation: Here, number of carbon atoms in the given fatty acid = 12. So, by putting n = 12

Number of cycles of ß-oxidation needed for the complete oxidation of fatty acid = $\frac{12}{\text{2}}\text{-1}\text{=}\text{5}$

Therefore, number of acetyl CoA produced from the complete oxidation of fatty acid =
  $\frac{12}{\text{2}}\text{=}6$

Activation		-2 ATP
Acetyl CoA	$6\times 10$ATP/Acetyl CoA	60ATP
NADH	$5\times 2.5$ATP/NADH	12.5 ATP
FADH2	$5\times 1.5$ATP/ FADH2	7.5 ATP
Total		78 ATP

Conclusions:

a. Thus, for complete oxidation of lauric acid five (5) cycles of ß-oxidation are needed.

b. Thus, from complete oxidation of lauric acid six (6) acetyl CoA are produced.

c. Thus, from the complete oxidation of lauric acid, 78 ATP is formed.