Q. 18.42 - An Introduction to General, Organic, and Biological Chemistry

Question

Refer to the diagram of the citric acid cycle in Figure $18.13$ to answer each of the following:

a. What is the yield of data-custom-editor="chemistry" ${\mathrm{CO}}_2$ molecules?

b. What are the four-carbon compounds?

c. What is the yield of data-custom-editor="chemistry" $\mathrm{GTP}$ molecules?

d. In which reactions are secondary alcohols oxidized?

Step-by-Step Solution

Answer

(a) The yield of ${\mathrm{CO}}_2$ molecules is two molecules

(b) The Succinyl-$\mathrm{CoA}$, succinate, fumarate, malate, and oxaloacetate are the four-carbon molecules in the citric acid cycle.

(c) The yield of $\mathrm{GTP}$ molecules is one molecule

(d) The reaction in which secondary alcohol oxidize is the citric acid cycle's decarboxylation process happens at stages $3$ and $4$ of the metabolic pathway.

Part (a) Step 1: Given information

We need to find out the yield of ${\mathrm{CO}}_2$ molecules

Part (a) Step 2: Explanation

The citric acid cycle produces two carbon dioxide molecules. One molecule of carbon dioxide was produced by the decarboxylation of isocitrate by isocitrate dehydrogenase, and another was produced by the decarboxylation of a ketoglutarate by a-ketoglutarate dehydrogenase.

Part (b) Step 1: Given information

We need to find out the four-carbon compounds 

Part (b) Step 2: Explanation

The Succinyl-$\mathrm{CoA}$, succinate, fumarate, malate, and oxaloacetate are the four-carbon molecules in the citric acid cycle. Succinyl-$\mathrm{CoA}$ is made from the decarboxylation-oxidation of $\mathrm{\alpha }$-ketoglutarate by $\mathrm{\alpha }$-ketoglutarate dehydrogenase; succinate is made from the hydrolysis of succinyl-$\mathrm{CoA}$ by succinyl-$\mathrm{CoA}$ synthetase; fumarate is made from the oxidation of succinate by succinate dehydrogenase; malate is made from the hydration of fumarate

Part (c) Step 1: Given information

We need to find out the yield of $\mathrm{GTP}$ molecules

Part (c) Step 2: Explanation

The citric acid cycle produces one molecule of $\mathrm{GTP}$. It is produced by the catalysis of succinyl-$\mathrm{CoA}$ synthetase during the hydrolysis of succinyl-$\mathrm{CoA}$ to yield succinate. The energy from the hydrolysis of succinyl-$\mathrm{CoA}$ to succinate is transferred to the condensation process of phosphate and GDP , resulting in the formation of a molecule of GTP.

Part (d) Step 1: Given information

We need to find the oxidation reaction of secondary alcohol.

Part (d) Step 2: Explanation

The citric acid cycle's decarboxylation process happens at stages $3$ and $4$ of the metabolic pathway. Step $3$ involved the decarboxylation of isocitrate to create $\mathrm{\alpha }$-ketoglutarate with the help of isocitrate dehydrogenase. In step $4$, $\mathrm{\alpha }$-ketoglutarate dehydrogenase catalyzes the decarboxylation of $\mathrm{\alpha }$-ketoglutarate to produce succinyl-$\mathrm{CoA}$.