In aerobic cellular respiration, hydrogen is recycled through a series of steps in the electron transport chain within the mitochondria of a cell. Here is a simplified explanation of how hydrogen is recycled in this process:
1. During glycolysis and the citric acid cycle, glucose is broken down into pyruvate and then further into carbon dioxide, producing NADH and FADH2 as carriers of high-energy electrons.
2. The NADH and FADH2 molecules then donate their high-energy electrons to the electron transport chain located in the inner mitochondrial membrane.
3. As these electrons move through the electron transport chain, they release energy that is used to pump hydrogen ions (H+) across the inner mitochondrial membrane, creating a gradient.
4. The hydrogen ions then flow back into the mitochondrial matrix through ATP synthase, an enzyme that uses the energy from their movement to convert ADP and inorganic phosphate into ATP, the cell's main energy currency.
5. At the end of the electron transport chain, oxygen acts as the final electron acceptor, combining with hydrogen ions and electrons to form water.
6. Through this process, the hydrogen atoms from glucose are effectively recycled, as they are carried by NADH and FADH2, used to create a proton gradient, and ultimately combine with oxygen to form water.
This recycling of hydrogen in aerobic cellular respiration is essential for the efficient production of ATP, providing energy for various cellular processes.
