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Question
How many times CO2 is released in aerobic respiration?
How many times CO2 is released in aerobic respiration?
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Solution
The correct option is B Three
Respiration proceeds in two stages. First stage is glycolysis, during which one molecule of hexose glucose is converted to two molecules of pyruvic acid. No oxygen is consumed nor any carbon dioxide is released during glycolysis. Glycolysis is followed by oxidative decarboxylation of pyruvic acid, in which each molecule of three carbon atom containing pyruvic acid is converted to two carbon atom containing acetyl CoA and a molecule of carbon dioxide is released. Next stage is the citric acid cycle, followed by the last stage the electron transport chain and oxidative phosphorylation. In the course of the citric acid cycle, two molecules of CO2 and the equivalent of eight hydrogen atoms (8 protons and 8 electrons) are removed, forming three NADH and one FADH2. The CO2 produced accounts for the two carbon atoms of the acetyl group, that entered the citric acid cycle. At the end of each cycle, the four carbon oxaloacetate (which condenses with acetyl CoA in the first reaction of citric acid cycle) has been regenerated, and the cycle continues. Thus three times carbon dioxide is released during the course of aerobic respiration- once during oxidative decarboxylation of pyruvate and two during the Krebs or citric acid cycle.
Respiration proceeds in two stages. First stage is glycolysis, during which one molecule of hexose glucose is converted to two molecules of pyruvic acid. No oxygen is consumed nor any carbon dioxide is released during glycolysis. Glycolysis is followed by oxidative decarboxylation of pyruvic acid, in which each molecule of three carbon atom containing pyruvic acid is converted to two carbon atom containing acetyl CoA and a molecule of carbon dioxide is released. Next stage is the citric acid cycle, followed by the last stage the electron transport chain and oxidative phosphorylation. In the course of the citric acid cycle, two molecules of CO2 and the equivalent of eight hydrogen atoms (8 protons and 8 electrons) are removed, forming three NADH and one FADH2. The CO2 produced accounts for the two carbon atoms of the acetyl group, that entered the citric acid cycle. At the end of each cycle, the four carbon oxaloacetate (which condenses with acetyl CoA in the first reaction of citric acid cycle) has been regenerated, and the cycle continues. Thus three times carbon dioxide is released during the course of aerobic respiration- once during oxidative decarboxylation of pyruvate and two during the Krebs or citric acid cycle.
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