# In what stage of cellular respiration is most of the carbon dioxide produced?

May 13, 2017

The Krebs Cycle

#### Explanation:

The Krebs cycle or the TCA cycle produces $\text{2 } C {O}_{2}$ for every $\text{1 molecule of acetyl CoA} .$

This occurs in Step 3 and Step 4 of the Krebs cycle.

In Step 3, $\textcolor{\mathmr{and} a n \ge}{\text{isocitrate}}$ is oxidized to become $\textcolor{b l u e}{\text{alpha-ketoglutarate}}$ by the rate-limiting enzyme, $\textcolor{red}{\text{isocitrate dehydrogenase}} .$

In Step 4, $\textcolor{b l u e}{\text{alpha-ketoglutarate}}$ undergoes a redox reaction, oxidizing to become $\textcolor{m a \ge n t a}{\text{succinyl-CoA}}$, also releasing $C {O}_{2}$ in the process.

Each step generates the coenzyme, $\text{NADH}$, an electron carrier which is going to be important in the next stage of cellular respiration, the electron transport chain.