The Krebs cycle includes reactions that release carbon dioxide.

The Krebs cycle includes reactions that release carbon dioxide.

• A. False
• B. True
• C. Only in plants
• D. Not related to energy production

Answer: (B)

During the Krebs cycle, carbon dioxide is released as parts of the carbon backbone are oxidized in decarboxylation steps. Specifically, the two carbons from acetyl-CoA are released as CO2 in separate steps—one when isocitrate is converted to α-ketoglutarate and another when α-ketoglutarate is converted to succinyl-CoA. These decarboxylation reactions are accompanied by the production of NADH (and one step also involves FADH2), which carry high-energy electrons to the electron transport chain to drive ATP synthesis. This cycle occurs in the mitochondria of aerobic organisms, including both plants and animals, so CO2 release is a normal part of energy production, not something exclusive to plants. Therefore, the statement is true.

During the Krebs cycle, carbon dioxide is released as parts of the carbon backbone are oxidized in decarboxylation steps. Specifically, the two carbons from acetyl-CoA are released as CO2 in separate steps—one when isocitrate is converted to α-ketoglutarate and another when α-ketoglutarate is converted to succinyl-CoA. These decarboxylation reactions are accompanied by the production of NADH (and one step also involves FADH2), which carry high-energy electrons to the electron transport chain to drive ATP synthesis. This cycle occurs in the mitochondria of aerobic organisms, including both plants and animals, so CO2 release is a normal part of energy production, not something exclusive to plants. Therefore, the statement is true.