Question

which of the following sequences represents the correct order in which metabolic reactions occur during the complete oxidation of glucose through aerobic respiration?
glucose → citric acid cycle → glycolysis → pyruvate oxidation → electron transport chain
glucose → pyruvate oxidation → glycolysis → electron transport chain → citric acid cycle
glucose → glycolysis → pyruvate oxidation → citric acid cycle → electron transport chain
glucose → glycolysis → citric acid cycle → pyruvate oxidation → electron transport chain
glucose → pyruvate oxidation → citric acid cycle → glycolysis → electron transport chain

Explanation:

• Glycolysis: Glucose is first broken down into pyruvate in the cytoplasm.
• Pyruvate oxidation: Pyruvate is transported into the mitochondria and oxidized to acetyl - CoA.
• Citric acid cycle: Acetyl - CoA enters the citric acid cycle (Krebs cycle) where more energy (in the form of \(NADH\), \(FADH_2\), and some ATP) is extracted.
• Electron transport chain: \(NADH\) and \(FADH_2\) from glycolysis, pyruvate oxidation, and the citric acid cycle donate electrons to the electron transport chain, which is used to generate a large amount of ATP through oxidative phosphorylation.

Answer:

glucose → glycolysis → pyruvate oxidation → citric acid cycle → electron transport chain