Chapter 25, Problem 25.25EP

(a)

Interpretation Introduction

Interpretation:

Whether “$\text{Acyl CoA}$ is a reactant” in the mitochondrial matrix or in the mitochondrial intermembrane space in the carnitine shuttle system associated with the $\beta -\text{oxidation}$ process has to be indicated.

Concept Introduction:

The fatty acids are broken down to provide energy. The breakdown of fatty acids is a three parts process. In the first part, the fatty acid is activated. In the second part, the transportation of fatty acid into the mitochondrial matrix is facilitated by a shuttle mechanism. In the third part, the fatty acid is readily oxidized, cycling through a series of four reactions. $\text{Acetyl CoA}$, ${\text{FADH}}_2$, and NADH are produced in this reaction.

The $\beta -\text{oxidation}$ pathway is defined as a repetitive series of four biochemical reactions in which $\text{acyl CoA}$ is degraded to $\text{acetyl CoA}$ by the removal of two carbon atoms at a time. NADH and ${\text{FADH}}_2$ are also produced in this pathway.

The first stage of fatty acid oxidation is the activation of fatty acids in the outer mitochondrial membrane. The fatty acid is activated by $\text{CoA}$ and ATP. The $\text{activated fatty acid}-\text{CoA}$ is called $\text{acyl CoA}$.

Answer to Problem 25.25EP

$\text{Acyl CoA}$ is a reactant in the intermembrane space.

Explanation of Solution

The enzymes that are needed for the oxidation of fatty acid are located in the mitochondrial matrix.  Acyl CoA cannot pass through the inner mitochondrial membrane to the mitochondrial matrix because it is too large. A shuttle mechanism that involves the molecule carnitine effects the entry of Acyl CoA into the mitochondrial matrix.

An overview of the transportation of Acyl CoA in the carnitine shuttle system associated with the $\beta -\text{oxidation}$ process is as follows:

Therefore, Acyl CoA is encountered as a reactant in the intermembrane space.

(b)

Interpretation Introduction

Interpretation:

Whether “carnitine enters the inner mitochondrial membrane” in the mitochondrial matrix or in the mitochondrial intermembrane space in the carnitine shuttle system associated with the $\beta -\text{oxidation}$ process has to be indicated.

Concept Introduction:

The fatty acids are broken down to provide energy. The breakdown of fatty acids is a three parts process. In the first part, the fatty acid is activated. In the second part, the transportation of fatty acid into the mitochondrial matrix is facilitated by a shuttle mechanism. In the third part, the fatty acid is readily oxidized, cycling through a series of four reactions. $\text{Acetyl CoA}$, ${\text{FADH}}_2$, and NADH are produced in this reaction.

The $\beta -\text{oxidation}$ pathway is defined as a repetitive series of four biochemical reactions in which $\text{acyl CoA}$ is degraded to $\text{acetyl CoA}$ by the removal of two carbon atoms at a time. NADH and ${\text{FADH}}_2$ are also produced in this pathway.

The first stage of fatty acid oxidation is the activation of fatty acids in the outer mitochondrial membrane. The fatty acid is activated by $\text{CoA}$ and ATP. The $\text{activated fatty acid}-\text{CoA}$ is called Acyl CoA.

Answer to Problem 25.25EP

Carnitine enters the inner mitochondrial membrane in the mitochondrial matrix.

Explanation of Solution

The enzymes that are needed for the oxidation of fatty acid are located in the mitochondrial matrix. $\text{Acyl CoA}$ cannot pass through the inner mitochondrial membrane to the mitochondrial matrix because it is too large. A shuttle mechanism that involves the molecule carnitine effects the entry of $\text{acyl CoA}$ into the mitochondrial matrix.

An overview of the transportation of $\text{acyl CoA}$ in the carnitine shuttle system associated with the $\beta -\text{oxidation}$ process is as follows:

Carnitine molecule shuttles the activated fatty acid molecules across the inner mitochondrial membrane. Therefore, carnitine enters the inner mitochondrial membrane in the mitochondrial matrix.

(c)

Interpretation Introduction

Interpretation:

Whether “carnitine is converted to acyl carnitine” in the mitochondrial matrix or in the mitochondrial intermembrane space in the carnitine shuttle system associated with the $\beta -\text{oxidation}$ process has to be indicated.

Concept Introduction:

The fatty acids are broken down to provide energy. The breakdown of fatty acids is a three parts process. In the first part, the fatty acid is activated. In the second part, the transportation of fatty acid into the mitochondrial matrix is facilitated by a shuttle mechanism. In the third part, the fatty acid is readily oxidized, cycling through a series of four reactions. $\text{Acetyl CoA}$, ${\text{FADH}}_2$, and NADH are produced in this reaction.

The $\beta -\text{oxidation}$ pathway is defined as a repetitive series of four biochemical reactions in which $\text{acyl CoA}$ is degraded to $\text{acetyl CoA}$ by the removal of two carbon atoms at a time. NADH and ${\text{FADH}}_2$ are also produced in this pathway.

The first stage of fatty acid oxidation is the activation of fatty acids in the outer mitochondrial membrane. The fatty acid is activated by $\text{CoA}$ and ATP. The $\text{activated fatty acid}-\text{CoA}$ is called $\text{acyl CoA}$.

The enzymes that are needed for the oxidation of fatty acid are located in the mitochondrial matrix. $\text{Acyl CoA}$ cannot pass through the inner mitochondrial membrane to the mitochondrial matrix because it is too large. A shuttle mechanism that involves the molecule carnitine effects the entry of $\text{acyl CoA}$ into the mitochondrial matrix.

Answer to Problem 25.25EP

Carnitine is converted to acyl carnitine in the mitochondrial intermembrane space.

Explanation of Solution

Acyl group present in $\text{acyl CoA}$ is transferred to carnitine. This results in the formation of acyl carnitine. Fatty acids are transported in the form of acyl carnitine across the inner mitochondrial membrane.

An overview of the transportation of $\text{acyl CoA}$ in the carnitine shuttle system associated with the $\beta -\text{oxidation}$ process is as follows:

Therefore, carnitine is converted to acyl carnitine in the mitochondrial intermembrane space.

(d)

Interpretation Introduction

Interpretation:

Whether “free $\text{CoA}$ is a reactant” in the mitochondrial matrix or in the mitochondrial intermembrane space in the carnitine shuttle system associated with the $\beta -\text{oxidation}$ process has to be indicated.

Concept Introduction:

The fatty acids are broken down to provide energy. The breakdown of fatty acids is a three parts process. In the first part, the fatty acid is activated. In the second part, the transportation of fatty acid into the mitochondrial matrix is facilitated by a shuttle mechanism. In the third part, the fatty acid is readily oxidized, cycling through a series of four reactions. $\text{Acetyl CoA}$, ${\text{FADH}}_2$, and NADH are produced in this reaction.

The $\beta -\text{oxidation}$ pathway is defined as a repetitive series of four biochemical reactions in which $\text{acyl CoA}$ is degraded to $\text{acetyl CoA}$ by the removal of two carbon atoms at a time. NADH and ${\text{FADH}}_2$ are also produced in this pathway.

The first stage of fatty acid oxidation is the activation of fatty acids in the outer mitochondrial membrane. The fatty acid is activated by $\text{CoA}$ and ATP. The $\text{activated fatty acid}-\text{CoA}$ is called $\text{acyl CoA}$.

The enzymes that are needed for the oxidation of fatty acid are located in the mitochondrial matrix. $\text{Acyl CoA}$ cannot pass through the inner mitochondrial membrane to the mitochondrial matrix because it is too large. A shuttle mechanism that involves the molecule carnitine effects the entry of $\text{acyl CoA}$ into the mitochondrial matrix.

Answer to Problem 25.25EP

Free $\text{CoA}$ is a reactant in the mitochondrial matrix.

Explanation of Solution

Acyl group present in $\text{acyl CoA}$ is transferred to carnitine. This results in the formation of acyl carnitine. Fatty acids are transported in the form of acyl carnitine across the inner mitochondrial membrane. Acyl group from acyl carnitine is transferred back to free $\text{CoA}$ in the mitochondrial matrix.

An overview of the transportation of $\text{acyl CoA}$ in the carnitine shuttle system associated with the $\beta -\text{oxidation}$ process is as follows:

Therefore, free $\text{CoA}$ is a reactant in the mitochondrial matrix.