Chapter 25, Problem 25.103EP

(a)

Interpretation Introduction

Interpretation:

Enoyl CoA is encountered in the process (1) glycerol metabolism to dihydroxyacetone phosphate, (2) β-oxidation pathway, (3) ketogenesis, and (4) lipogenesis has to be identified.

Concept introduction:

Lipogenesis is the process employed for the synthesis of fatty acid. The starting precursor for the synthesis is acetyl CoA. The enzyme employed for the process is fatty acid synthase. It is a multienzyme complex that ties the reaction responsible for the synthesis of fatty acid. The fatty acid is synthesized in two parts. In the first part, there is citrate-malate shuttle system and in the second part, there is a cyclic process to synthesize saturated fatty acid.

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. In these series of reactions, acyl CoA is degraded to acetyl CoA. This pathway is termed as β-oxidation pathway.

Ketogenesis is a metabolic process by which ketone bodies are produced by the breakdown of fatty acids and ketogenic amino acids. This metabolic process supplies our organs with needed energy under certain circumstances such as starvation. Fatty acid molecules degrade into acetyl CoA which are utilized as reactants in the process of ketogenesis. These molecules of acetyl CoA undergo the process of condensation twice, followed by chain cleavage and hydrogenation to produce ketone bodies.

Triacylglycerol mobilization is an ongoing process in which triacylglycerols that are stored in the adipose tissue are hydrolyzed. Fatty acids and glycerol are the products of triacylglycerol mobilization. The products are released into the bloodstream.

After entering the bloodstream, the glycerol travels to the kidneys or liver. The first stage of glycerol metabolism occurs in the liver or kidney where it is converted to $\text{dihydroxyacetone phosphate}$. The overall equation for glycerol metabolism is as follows:

$\text{Glycerol}+\text{ATP}+{\text{NAD}}^{+}\to \text{Dihydroxyacetone phosphate}+\text{ADP}+\text{NADH}+{\text{H}}^{+}$

Answer to Problem 25.103EP

Enoyl CoA is encountered inβ-oxidation pathway.

Explanation of Solution

Enoyl CoA is a product in step 1 of the β-oxidation pathway.

Step 1 is a dehydrogenation reaction. In step 1, acyl CoA is converted into trans-enoyl CoA with the help of oxidizing agent FAD. This reaction is catalyzed by acyl CoA dehydrogenase enzyme. The reaction for step 1 is as follows:

(b)

Interpretation Introduction

Interpretation:

FAD is encountered in the process (1) glycerol metabolism to dihydroxyacetone phosphate, (2) β-oxidation pathway, (3) ketogenesis, and (4) lipogenesis has to be identified.

Concept introduction:

Lipogenesis is the process employed for the synthesis of fatty acid. The starting precursor for the synthesis is acetyl CoA. The enzyme employed for the process is fatty acid synthase. It is a multienzyme complex that ties the reaction responsible for the synthesis of fatty acid. The fatty acid is synthesized in two parts. In the first part, there is citrate-malate shuttle system and in the second part, there is a cyclic process to synthesize saturated fatty acid.

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. In these series of reactions, acyl CoA is degraded to acetyl CoA. This pathway is termed as β-oxidation pathway.

Ketogenesis is a metabolic process by which ketone bodies are produced by the breakdown of fatty acids and ketogenic amino acids. This metabolic process supplies our organs with needed energy under certain circumstances such as starvation. Fatty acid molecules degrade into acetyl CoA which are utilized as reactants in the process of ketogenesis. These molecules of acetyl CoA undergo the process of condensation twice, followed by chain cleavage and hydrogenation to produce ketone bodies.

Triacylglycerol mobilization is an ongoing process in which triacylglycerols that are stored in the adipose tissue are hydrolyzed. Fatty acids and glycerol are the products of triacylglycerol mobilization. The products are released into the bloodstream.

After entering the bloodstream, the glycerol travels to the kidneys or liver. The first stage of glycerol metabolism occurs in the liver or kidney where it is converted to $\text{dihydroxyacetone phosphate}$. The overall equation for glycerol metabolism is as follows:

$\text{Glycerol}+\text{ATP}+{\text{NAD}}^{+}\to \text{Dihydroxyacetone phosphate}+\text{ADP}+\text{NADH}+{\text{H}}^{+}$

Answer to Problem 25.103EP

FAD is encountered in the β-oxidation pathway.

Explanation of Solution

FAD is an oxidizing agent employed in step 1 of the β-oxidation pathway.

Step 1 is a dehydrogenation reaction. In step 1, acyl CoA is converted into trans-enoyl CoA with the help of oxidizing agent FAD. FAD gets reduced to form FADH₂ and oxidizes acyl CoA in this step. This reaction is catalyzed by acyl CoA dehydrogenase enzyme. The reaction for step 1 is as follows:

(c)

Interpretation Introduction

Interpretation:

β–Hydroxybutyrate is encountered in the process (1) glycerol metabolism to dihydroxyacetone phosphate, (2) β-oxidation pathway, (3) ketogenesis, and (4) lipogenesis has to be identified.

Concept introduction:

Lipogenesis is the process employed for the synthesis of fatty acid. The starting precursor for the synthesis is acetyl CoA. The enzyme employed for the process is fatty acid synthase. It is a multienzyme complex that ties the reaction responsible for the synthesis of fatty acid. The fatty acid is synthesized in two parts. In the first part, there is citrate-malate shuttle system and in the second part, there is a cyclic process to synthesize saturated fatty acid.

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. In these series of reactions, acyl CoA is degraded to acetyl CoA. This pathway is termed as β-oxidation pathway.

Ketogenesis is a metabolic process by which ketone bodies are produced by the breakdown of fatty acids and ketogenic amino acids. This metabolic process supplies our organs with needed energy under certain circumstances such as starvation. Fatty acid molecules degrade into acetyl CoA which are utilized as reactants in the process of ketogenesis. These molecules of acetyl CoA undergo the process of condensation twice, followed by chain cleavage and hydrogenation to produce ketone bodies.

Triacylglycerol mobilization is an ongoing process in which triacylglycerols that are stored in the adipose tissue are hydrolyzed. Fatty acids and glycerol are the products of triacylglycerol mobilization. The products are released into the bloodstream.

After entering the bloodstream, the glycerol travels to the kidneys or liver. The first stage of glycerol metabolism occurs in the liver or kidney where it is converted to $\text{dihydroxyacetone phosphate}$. The overall equation for glycerol metabolism is as follows:

$\text{Glycerol}+\text{ATP}+{\text{NAD}}^{+}\to \text{Dihydroxyacetone phosphate}+\text{ADP}+\text{NADH}+{\text{H}}^{+}$

Answer to Problem 25.103EP

β–Hydroxybutyrate is encountered in ketogenesis.

Explanation of Solution

β–Hydroxybutyrate is encountered in step 4 of ketogenesis.

Step 4 is a dehydrogenation reaction. In step 4, acetoacetate is reduced to form β–hydroxybutyrate with the help of reducing agent NADH. This reaction is catalyzed by β–hydroxybutyrate dehydrogenase enzyme. The reaction for step 4 is as follows:

(d)

Interpretation Introduction

Interpretation:

Glycerol 3-phosphate is encountered in the process (1) glycerol metabolism to dihydroxyacetone phosphate, (2) β-oxidation pathway, (3) ketogenesis, and (4) lipogenesis has to be identified.

Concept introduction:

Lipogenesis is the process employed for the synthesis of fatty acid. The starting precursor for the synthesis is acetyl CoA. The enzyme employed for the process is fatty acid synthase. It is a multienzyme complex that ties the reaction responsible for the synthesis of fatty acid. The fatty acid is synthesized in two parts. In the first part, there is citrate-malate shuttle system and in the second part, there is a cyclic process to synthesize saturated fatty acid.

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. In these series of reactions, acyl CoA is degraded to acetyl CoA. This pathway is termed as β-oxidation pathway.

Ketogenesis is a metabolic process by which ketone bodies are produced by the breakdown of fatty acids and ketogenic amino acids. This metabolic process supplies our organs with needed energy under certain circumstances such as starvation. Fatty acid molecules degrade into acetyl CoA which are utilized as reactants in the process of ketogenesis. These molecules of acetyl CoA undergo the process of condensation twice, followed by chain cleavage and hydrogenation to produce ketone bodies.

Triacylglycerol mobilization is an ongoing process in which triacylglycerols that are stored in the adipose tissue are hydrolyzed. Fatty acids and glycerol are the products of triacylglycerol mobilization. The products are released into the bloodstream.

After entering the bloodstream, the glycerol travels to the kidneys or liver. The first stage of glycerol metabolism occurs in the liver or kidney where it is converted to $\text{dihydroxyacetone phosphate}$. The overall equation for glycerol metabolism is as follows:

$\text{Glycerol}+\text{ATP}+{\text{NAD}}^{+}\to \text{Dihydroxyacetone phosphate}+\text{ADP}+\text{NADH}+{\text{H}}^{+}$

Answer to Problem 25.103EP

Glycerol 3-phosphate is encountered in glycerol metabolism to dihydroxyacetone phosphate.

Explanation of Solution

Glycerol 3-phosphate is a product in step 1 of the glycerol metabolism.

Glycerol metabolism to dihydroxyacetone phosphate is a two-step process. In the first step, glycerol is converted into glycerol-3 phosphate and in the second step, glycerol-3 phosphate is converted into dihydroxyacetone phosphate with the help of oxidizing agent NAD⁺. The enzyme employed in step 1 is glycerol kinase. The reaction for step 1 is as follows: