Final answer:
Option 4: NADH is consumed during the Electron Transport Chain, which is the fourth stage of cellular respiration, while it is produced earlier in glycolysis, pyruvate oxidation, and the citric acid cycle.
Step-by-step explanation:
The stage(s) of cellular respiration that consume NADH are primarily phase 4, the Electron Transport Chain. While NADH is produced in stage 1 (Glycolysis), phase 2 (Pyruvate oxidation), and phase 3 (the Citric acid cycle), it is not consumed in these stages. Instead, these first three stages generate NADH and FADH2, which are then used in the Electron Transport Chain. In this fourth stage, the high-energy electrons from NADH and FADH2 are transferred to the electron transport chain in the mitochondrial membrane, where they are used to pump protons across the inner membrane, creating a proton gradient that drives the synthesis of ATP from ADP, and regenerating NAD⁺, which is then available to be used again in glycolysis.
The stage(s) of cellular respiration that consume NAD⁺H are glycolysis, pyruvate oxidation, and the citric acid cycle. In glycolysis, NAD⁺ is reduced to NADH when glucose is converted into pyruvate. In pyruvate oxidation, each pyruvate is converted into Acetyl CoA, producing NADH in the process. Lastly, in the citric acid cycle, NAD⁺ is reduced to NADH as part of the cycle to generate ATP. The electron transport chain, on the other hand, uses NADH and FADH₂ to generate ATP, but it does not consume NAD⁺H.