Chapter 24, Problem 64P

Interpretation Introduction

(a)

Interpretation:

The a and β carbons of docosanoic acid ${\text{C}}_{21}{\text{H}}_{43}\text{COOH}$ should be labeled.

Concept Introduction:

Acyl CoA is defined as a group of coenzymes that metabolizes fatty acids. All the acyl CoA's are susceptible to β-oxidation forming Acetyl CoA. Then, this acetyl CoA formed will enter the citric acid cycle forming several equivalents of ATP. This is the way by which fats are converted to ATP, a universal energy carrier.

Structure of Acyl CoA is as follows:

 

Answer to Problem 64P

The a and β carbons of docosanoic acid ${\text{C}}_{21}{\text{H}}_{43}\text{COOH}$ is shown as follows:

 

Explanation of Solution

Fatty acids are catabolized through the β-oxidation process in which $2-$ carbon acetyl CoA units cleaved sequentially from the fatty acid. Oxidation of β-carbon to the carbonyl of a thio-ester which then undergoes cleavage between the alpha and beta carbons.

 

Interpretation Introduction

(b)

Interpretation:

The acyl CoA derived from the given docosanoic acid, ${\text{C}}_{21}{\text{H}}_{43}\text{COOH}$ should be drawn.

Concept Introduction:

Acyl CoA is defined as a group of coenzymes that metabolizes fatty acids. All the acyl CoA's are susceptible to β-oxidation forming Acetyl CoA. Then, this acetyl CoA formed will enter the citric acid cycle forming several equivalents of ATP. This is the way by which fats are converted to ATP, a universal energy carrier.

Structure of Acyl CoA is as follows:

 

Answer to Problem 64P

The acyl CoA derivative of the given docosanoic acid, ${\text{C}}_{21}{\text{H}}_{43}\text{COOH}$ .is as follows:

 

Explanation of Solution

Acyl CoA is defined as a group of coenzymes that metabolizes fatty acids. Acyl CoA's are susceptible to β-oxidation forming Acetyl CoA. Structure of Acyl CoA is as follows:

Here, R group will depend on the chain of the fatty acid.

 

The acyl CoA derivative of the given docosanoic acid is as follows:

 

Interpretation Introduction

(c)

Interpretation:

The number of acetyl CoA molecules formed from the complete β-oxidation of the given fatty acid docosanoic acid, ${\text{C}}_{21}{\text{H}}_{43}\text{COOH}$ should be determined.

Concept Introduction:

Acyl CoA is defined as a group of coenzymes that metabolizes fatty acids. All the acyl CoA's are susceptible to β-oxidation forming Acetyl CoA. Then, this acetyl CoA formed will enter the citric acid cycle forming several equivalents of ATP. This is the way by which fats are converted to ATP, a universal energy carrier.

Answer to Problem 64P

The number of acetyl CoA molecules produced from the complete catabolism of the given fatty acid, docosanoic acid $\left({\text{C}}_{21}{\text{H}}_{43}\text{COOH}\right)$ will be $11$.

Explanation of Solution

The number of carbon atoms present in fatty acid determines the number of acetyl CoA formed and a number of cycles during the complete catabolism of the fatty acid. The number of molecules of acetyl CoA produced will be equals to one-half the number of carbon atoms present in the original fatty acid.

In the given fatty acid docosanoic acid, ${\text{C}}_{21}{\text{H}}_{43}\text{COOH}$ have $22$ carbon atoms, so the number of acetyl CoA molecules produced from the complete catabolism will be $11$.

Interpretation Introduction

(d)

Interpretation:

The number of cycles produced complete β-oxidation of the given fatty acid, docosanoic acid $\left({\text{C}}_{21}{\text{H}}_{43}\text{COOH}\right)$ should be determined.

Concept Introduction:

Acyl CoA is defined as a group of coenzymes that metabolizes fatty acids. All the acyl CoA's are susceptible to β-oxidation forming Acetyl CoA. Then, this acetyl CoA formed will enter the citric acid cycle forming several equivalents of ATP. This is the way by which fats are converted to ATP, a universal energy carrier.

Answer to Problem 64P

Number of cycles produced by the complete β-oxidation of the given fatty acid, docosanoic acid $\left({\text{C}}_{21}{\text{H}}_{43}\text{COOH}\right)$ is $10$

Explanation of Solution

The complete β-oxidation of the given fatty acid involves $\frac{n}{2}-1\text{cycles}$ . Here $n=\text{number}\text{of}\text{carbon}\text{atoms}$

Here $n=22$

  $\text{Number}\text{of}\text{cycles}=\frac{22}{2}-1=11-1=10$

Interpretation Introduction

(e)

Interpretation:

The number of molecules of ATP formed from the complete catabolism of the given fatty acid, docosanoic acid $\left({\text{C}}_{21}{\text{H}}_{43}\text{COOH}\right)$ should be determined.

Concept Introduction:

Acyl CoA is defined as a group of coenzymes that metabolizes fatty acids. All the acyl CoA's are susceptible to β-oxidation forming Acetyl CoA. Then, this acetyl CoA formed will enter the citric acid cycle forming several equivalents of ATP. This is the way by which fats are converted to ATP, a universal energy carrier.

Answer to Problem 64P

The total $148$ ATP molecules formed from the complete catabolism of the given fatty acid, docosanoic acid $\left({\text{C}}_{21}{\text{H}}_{43}\text{COOH}\right)$.

Explanation of Solution

The number of ATP molecules generated by the complete catabolism of the given docosanoic acid $\left({\text{C}}_{21}{\text{H}}_{43}\text{COOH}\right)$ is as follows:

1. Docosanoic acid is converted into acyl CoA which requires energy is gained by the hydrolysis of $\text{2}\text{P}-\text{O}$, this is equivalent to the energy released when 2ATP is converted to 2ADP.
2. Each cycle consists of four steps that produce one molecule of acetyl CoA, one molecule of NADH and one molecule of ${\text{FADH}}_2$ . To cleave $10\text{C}-\text{C}$ , ten cycle will take place producing $10\text{NADH}\text{and}10{\text{FADH}}_2$ .

As,

  $1\text{NADH}\text{=}\text{2}\text{.5}\text{ATP}$

  $1{\text{FADH}}_2=1.5\text{ATP}$

  $1\text{Acetyl CoA =10 ATP}$

Total ATPs produced from NADH is:

  $\begin{array}{c}\text{10}\text{NADH}\text{=}10\times \text{2}\text{.5}\text{ATP}\\ \text{=}\text{25}\text{ATP}\end{array}$

Total ATPs produced from ${\text{FADH}}_2$ is:

  $\begin{array}{c}10{\text{FADH}}_2\text{=}10\times 1.\text{5}\text{ATP}\\ \text{=}\text{15}\text{ATP}\end{array}$

Total ATPs produced from acetyl CoA is:

  $\begin{array}{c}11\text{acetyl CoA}\text{=}11\times 10\text{ATP}\\ \text{=}\text{110}\text{ATP}\end{array}$

As, the initiation of this catabolism requires energy in the form of ATP which is 2 equivalent so, the total number of ATPs generated during the complete catabolism of the given fatty acid is as follows:

Total ATPs produced from NADH + Total ATPs produced from ${\text{FADH}}_2$ + Total ATPs produced from acetyl CoA − 2ATP which is used in the initiation of the catabolism process = $25\text{ATP}+15\text{ATP}+110\text{ATP}-2\text{ATP}\text{=148}\text{ATPs}$