The process of aerobic respiration occurs in three different stages:
  1. Glycolysis
  2. Krebs cycle
  3. Electron transport chain
The process of cellular respiration
1. Glycolysis (Glucose splitting):
  • Both aerobic and anaerobic respiration begin with this process.
  • During this process, one molecule of glucose (6 carbon) is broken down into two pyruvic acid molecules (3 carbon).
  • It occurs in the cytoplasm of the cell.
Steps involved in glycolysis
2.  Krebs cycle:
  • It is the second stage of cellular respiration and occurs in the mitochondrial matrix.
  • Sir Hans Krebs discovered it. Hence it is known as the Krebs cycle.
  • The two molecules of pyruvic acid produced in the glycolysis enter into the mitochondria after glycolysis.
  • During this cycle, pyruvic acid is oxidized into \(CO_2\) and water.
  • Krebs cycle is also known as the Tricarboxylic Acid Cycle (TCA).
Pictorial representation of Krebs cycle and ETC
3. Electron Transport Chain:
  • This involves a system of electron transport chain (ETC) found on the inner mitochondrial membrane.
  • During this, the \(NADH_2\) and \(FADH_2\) molecules produced in the glycolysis and Krebs cycle are oxidized to \(NAD^+\) and \(FAD^+\) to release the energy via electrons.
  • As these electrons move through the system of the electron chain, they release the energy that the ADP traps to synthesize ATP. This is known as oxidative phosphorylation as a phosphate group is added to ATP.
  • \(O_2\) serves as the final acceptor electrons and thereby gets reduced to water.