How much ATP does one glucose give, and why does the brain need oxygen to get it? · Grey Matter

Glycolysis, in the cytoplasm and without oxygen, splits glucose into two pyruvates for a net gain of 2 ATP.

How much ATP does one glucose give, and why does the brain need oxygen to get it?

Glycolysis, in the cytoplasm and without oxygen, splits glucose into two pyruvates for a net gain of 2 ATP. Oxidising those pyruvates completely in the mitochondria, through the citric acid cycle and the electron transport chain, brings the total to about 30 to 32 ATP per glucose, by current estimates (older textbooks say 36 to 38, from higher assumed yields per NADH). Oxygen is the final acceptor of the electrons in that chain, so without it the mitochondria stop and the cell is left with the glycolytic 2. For an organ that spends its energy as fast as the brain does, a fifteenfold difference in yield is the difference between working and failing.