How many ATP are produced in aerobic respiration?

In aerobic respiration, up to 38 ATP molecules can be produced from one molecule of glucose.

While the theoretical maximum ATP yield from aerobic respiration is often cited as 38, the actual amount can vary slightly depending on cellular conditions and the efficiency of the electron transport chain. This number is an estimate based on:

• Glycolysis: Produces 2 ATP (net) and 2 NADH.
• Pyruvate Decarboxylation: Produces 2 NADH.
• Krebs Cycle (Citric Acid Cycle): Produces 2 ATP, 6 NADH, and 2 FADH2.
• Electron Transport Chain (ETC): This is where the majority of ATP is generated through oxidative phosphorylation. The NADH and FADH2 produced in the earlier stages donate electrons to the ETC, which ultimately leads to the production of ATP. Each NADH theoretically yields 2.5 ATP and each FADH2 yields 1.5 ATP.

Therefore, using these theoretical yields:

• 10 NADH x 2.5 ATP/NADH = 25 ATP
• 2 FADH2 x 1.5 ATP/FADH2 = 3 ATP

Adding the ATP produced directly in glycolysis and the Krebs cycle:

2 ATP (Glycolysis) + 2 ATP (Krebs Cycle) + 25 ATP (from NADH) + 3 ATP (from FADH2) = 32 ATP

However, taking into account the ATP produced in the cytoplasm from Glycolysis and the cost of transporting the NADH molecules produced during glycolysis, the total comes to approximately 30-32 ATP. The 38 ATP estimate includes the maximum theoretical yield.

The number of ATP molecules generated during aerobic respiration can be thought of in this way:

It's important to note that these are estimations, and the actual yield can vary depending on the cell type and conditions.