What are the stages of aerobic respiration?

Aerobic respiration consists of four stages: glycolysis, the link reaction, the Krebs cycle, and the electron transport chain.

Aerobic respiration is a process that occurs in the mitochondria of cells, where glucose is broken down to produce ATP, the energy currency of the cell. This process requires oxygen, hence the term 'aerobic'. It consists of four main stages: glycolysis, the link reaction, the Krebs cycle, and the electron transport chain.

The first stage, glycolysis, occurs in the cytoplasm of the cell. One molecule of glucose, a six-carbon sugar, is split into two molecules of a three-carbon sugar. This process produces two molecules of ATP and two molecules of NADH, a carrier of high-energy electrons.

The second stage, the link reaction, takes place in the mitochondria. Each three-carbon sugar from glycolysis is converted into a two-carbon molecule known as acetyl CoA. This process also produces one molecule of NADH and releases one molecule of carbon dioxide.

The third stage, the Krebs cycle, also occurs in the mitochondria. The acetyl CoA is combined with a four-carbon molecule to form a six-carbon molecule, which is then broken down in a series of steps to regenerate the four-carbon molecule. This cycle produces two molecules of ATP, eight molecules of NADH, and two molecules of FADH2, another carrier of high-energy electrons. It also releases four molecules of carbon dioxide.

The final stage, the electron transport chain, is where the majority of ATP is produced. The high-energy electrons carried by NADH and FADH2 are passed along a series of proteins in the inner mitochondrial membrane. This process pumps protons across the membrane, creating a gradient that drives the synthesis of ATP. Oxygen is the final electron acceptor in this process, combining with the electrons and protons to form water. This stage produces approximately 34 molecules of ATP.

In total, aerobic respiration can produce up to 38 molecules of ATP from one molecule of glucose, making it a highly efficient process for energy production in cells.