3) How many carbon dioxide molecules are liberated after each cycle of the Krebs cycle? For a single glucose how many carbon dioxide molecules were already liberated by the aerobic respiration at that point?
To determine the number of carbon dioxide molecules liberated after each cycle of the Krebs cycle, you need to understand the steps involved in this metabolic pathway.
The Krebs cycle, also known as the citric acid cycle or the tricarboxylic acid (TCA) cycle, is a series of chemical reactions that occur in the mitochondria of eukaryotic cells. It is an integral part of aerobic respiration and is responsible for generating energy in the form of ATP.
During each cycle of the Krebs cycle, a single acetyl-CoA molecule, derived from the breakdown of glucose, undergoes a series of reactions. In the process, two carbon dioxide (CO2) molecules are liberated, along with the production of three molecules of nicotinamide adenine dinucleotide (NADH), one molecule of flavin adenine dinucleotide (FADH2), and one molecule of guanosine triphosphate (GTP).
For a single glucose molecule, the initial step in aerobic respiration is glycolysis, which breaks down glucose into two molecules of pyruvate. During glycolysis, two molecules of NADH are produced.
Subsequently, each pyruvate enters the mitochondria and undergoes decarboxylation, resulting in the formation of acetyl-CoA. Since two pyruvate molecules are generated per glucose molecule, two molecules of NADH are produced during this step as well.
Considering the above information, for a single glucose molecule undergoing complete aerobic respiration, a total of six NADH molecules are produced: two from glycolysis, two from the conversion of pyruvate to acetyl-CoA, and two from each cycle of the Krebs cycle. Additionally, two molecules of FADH2 are produced from each cycle of the Krebs cycle.
Therefore, after each cycle of the Krebs cycle, a total of two carbon dioxide molecules are liberated, and a total of six carbon dioxide molecules are already liberated by the aerobic respiration of a single glucose molecule at that point.