### Theory:

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.
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