How does aerobic respiration release energy from glucose?
Energy is released using NAD+, FADH, and ATP Synthase.
Cells breakdown glucose molecules first during the process known as glycolysis. The glucose molecule is broken down into two pyruvate molecules and electrons are released. These electrons are picked up by NAD+. Once NAD+ has picked up these electrons, it becomes NADH. Two ATP molecules are also made (ATP transfers chemical energy between cells; it is sort of like a currency in this regard).
The next step is the Krebs cycle, also known as the citric acid cycle. During this step of the process, the pyruvate molecules are converted to Acetyl CoA, these molecules are then broken down even further, releasing electrons and ATP. As in the previous step, NAD+ picks up the released electrons, becoming NADH, as does FADH, which becomes FADH2.
Lastly, we have oxidative phosphorylation, which occurs in the inner membrane of the mitochondria (or the cytoplasm of prokaryotic cells). When NAD+ and FADH picked up electrons previously, they lost hydrogen atoms.
These hydrogen atoms now pump against the concentration gradient. Proteins in the membrane undergo active transport, moving the hydrogen atoms into one concentrated area. Next, the hydrogen atoms go through ATP Synthase, which turns out a lot of ATP.
To learn more, see the following video: