18.96 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify each of the following reactions in the β oxidation of palmitic acid, a C₁₆ fatty acid, as (1) activation, (2) first oxidation, (3) hydration, (4) second oxidation, (5) cleavage (thiolysis): 

a. Palmitoyl CoA and FAD form $\alpha ,\beta$ unsaturated fatty acids.

b. $\mathrm{\beta }$-ketopalmitoyal CoA forms myristoyl CoA and acetyl CoA.

c. Palmitic acid, CoA, and ATP from palmitoyal CoA .

d. $\alpha ,\beta$ unsaturated  palmitoyal CoA  and water from  $\mathrm{\beta }$ -hydroxy palmitoyal CoA.

e. $\mathrm{\beta }$ -hydroxy palmitoyal CoA and NAD⁺ from $\mathrm{\beta }$-ketopalmitoyal CoA and NADH + H⁺

Step-by-Step Solution

Answer

a. first oxidation

b. Cleavage

c. Activation

d. Hydration followed by Second oxidation

e. Second oxidation

Step 1: Part (a) Given information

Palmitoyl CoA and FAD form $\mathrm{\alpha },\mathrm{\beta }$ unsaturated fatty acids. 

Step 1: Part (a) Explanation

The first step is oxidation. 

The dehydrogenation of fatty acyl CoA forms a trans double bond between alpha and beta carbon. In this step, an electron is transferred to FAD.

Step 1: Part (b) Given information

$\mathrm{\beta }$-ketopalmitoyal CoA forms myristoyl CoA and acetyl CoA. 

Step 2: Part (b) Explanation

This is the fifth step which is cleavage which is known as thiolysis.

Step 1: Part (c) Explanation

Palmitic acid, CoA, and ATP from palmitoyal CoA . 

It is the first step that is the activation.

Step 1: Part (d) Given information

$\mathrm{\alpha },\mathrm{\beta }$ unsaturated palmitoyal CoA and water from $\mathrm{\beta }$ -hydroxy palmitoyal CoA. 

Step 2; Part (d) Explanation

This step is the hydration process followed by second oxidation.

Second oxidation:

Step 1:Part (e) Given information

$\mathrm{\beta }$ -hydroxy palmitoyal CoA and NAD⁺ from $\mathrm{\beta }$-ketopalmitoyal CoA and NADH + H⁺

Step 2: Part (e) Explanation

This step is also second oxidation.