What is the net ATP gain from one glucose?

The net ATP gain from one glucose molecule during aerobic respiration is 38 ATP in prokaryotes and about 36 ATP in eukaryotes. This number comes from the complete breakdown of glucose into carbon dioxide and water through glycolysis, Krebs cycle, and the electron transport chain.

Glucose is the main energy source for cells. When glucose is broken down, energy is released in the form of ATP (adenosine triphosphate). The process involves three main stages:

• Glycolysis: Takes place in the cytoplasm. From one glucose, it produces 2 ATP directly and 2 NADH (which later yield ATP in the electron transport chain).
• Krebs Cycle (Citric Acid Cycle): Occurs in mitochondria. Each glucose (after converting into 2 pyruvate molecules) generates 2 ATP, 6 NADH, and 2 FADH2.
• Electron Transport Chain (ETC): Located in the inner mitochondrial membrane. NADH and FADH2 donate electrons, producing the bulk of ATP (about 34).

ATP Accounting:

In eukaryotes, some ATP is lost because NADH from glycolysis has to be transported into mitochondria, leading to a slightly lower yield compared to prokaryotes. Overall, one glucose molecule gives about 36–38 ATP depending on the type of organism.