In aerobic respiration, what happens after the Krebs cycle?

After the Krebs cycle in aerobic respiration, the next step involves the electron transport chain. This sequence takes place in the inner mitochondrial membrane and is crucial for the production of ATP through oxidative phosphorylation. During the Krebs cycle, high-energy electron carriers such as NADH and FADH2 are generated. These carriers then transport their electrons to the electron transport chain, where they are used to create a proton gradient across the mitochondrial membrane.

As electrons move through the chain, they facilitate the pumping of protons from the mitochondrial matrix to the intermembrane space, creating a gradient. This gradient is harnessed by ATP synthase to produce ATP, the energy currency of the cell, as protons flow back into the matrix. The process also involves the final electron acceptor, oxygen, which combines with the electrons and protons to form water.

The other options refer to processes that do not occur immediately after the Krebs cycle in the context of aerobic respiration. Fermentation typically occurs in the absence of oxygen, glycolysis happens before the Krebs cycle, and while NADH is recycled during cellular respiration, this recycling is a part of the overall electron flow and not a distinct step following the Krebs cycle. Thus, the electron transport chain is the clear next stage in aerobic