Q. 18.55 - An Introduction to General, Organic, and Biological Chemistry

Question

What is the ATP energy yield associated with each of the following?

a. $\mathrm{NADH} \to {\mathrm{NAD}}^{+}$ 

b. $\mathrm{glucose}\to 2 \mathrm{pyruvate}$

c. $2 \mathrm{pyruvate} \to 2 \mathrm{acetyl} \mathrm{CoA} + 2{\mathrm{CO}}_2$

d. $\mathrm{acetyl} \mathrm{CoA} \to 2{\mathrm{CO}}_2$

Step-by-Step Solution

Answer

(a) The $3 \mathrm{ATP}$ energy is released during oxidation of NADH.

(b) The $6 \mathrm{ATP}$ energy is released during the given reaction i.e. $\mathrm{glucose} \to 2 \mathrm{pyruvate}$

(c) The $6 \mathrm{ATP}$ energy is released during the given reaction i.e. $2 \mathrm{pyruvate} \to 2 \mathrm{acetyl} \mathrm{CoA} + 2{\mathrm{CO}}_2$

(d) The $12 \mathrm{ATP}$ energy is released during the given reaction i.e. $\mathrm{acetyl} \mathrm{CoA} \to 2{\mathrm{CO}}_2$

Part (a) Step 1: Given information

We need to find the yield of ATP in the given reaction i.e. $\mathrm{NADH} \to {\mathrm{NAD}}^{+}$

Part (a) Step 2: Explnation

We know that

The energy produced by NADH's oxidation when it reaches electron transport complex I is used to make $3 \mathrm{ATP}$. The  equation of NADH  is

data-custom-editor="chemistry" $\mathrm{NADH}+{\mathrm{H}}^{+}+\frac{1}{2}{\mathrm{O}}_2+3\mathrm{ADP}+3{\mathrm{P}}_{\mathrm{i}}\to {\mathrm{NAD}}^{+}+{\mathrm{H}}_2\mathrm{O}+3\mathrm{ATP}$

Part (b) Step 1: Given information

We need to find the yield of ATP in the given reaction i.e. $\mathrm{glucose}\to 2\mathrm{pyruvate}$

Part (b) Step 2: Explanation

We know that

Energy is stored in two NADH molecules and two ATP molecules as a result of glucose oxidation. The hydrogen ions and electrons from NADH are shuttled from the cytoplasm to the mitochondria, resulting in ${\mathrm{FADH}}_2$. As a result, only two ATP are produced when electrons are transferred from NADH in the cytoplasm to ${\mathrm{FADH}}_2$.

Six ATP are created in glycolysis: four from the two NADH and two from phosphorylation.

Part (c) Step 1: Given information

We need to find the yield of ATP in the given reaction i.e. $2 \mathrm{pyruvate} \to 2 \mathrm{acetyl} \mathrm{CoA} + 2{\mathrm{CO}}_2$

Part (c) Step 2: Explanation

We know that

Under anaerobic conditions, pyruvate reaches to the mitochondria. Their pyruvate is oxidized to produce $\mathrm{acetyl}-\mathrm{CoA}, {\mathrm{CO}}_2,\mathrm{NADH}$. And as we all know $1 \mathrm{NADH}$ produces three ATP.

Therefore, a total of six ATP are produced

Part (d) Step 1: Given information

We need to find the yield of ATP in the given reaction i.e. $\mathrm{acetyl} \mathrm{CoA}\to 2{\mathrm{CO}}_2$

Part (d) Step 2: Explanation

We know that

In one turn of the citric acid cycle, two ${\mathrm{CO}}_2$, three NADH, one ${\mathrm{FADH}}_2$, and one ATP are created via direct phosphate transfer. As a result, one cycle of the citric acid cycle yields twelve ATP.