Respiration Releases Chemical Energy in Biological Processes

Respiration is a series of biochemical reactions that occurs in all living organisms.
It involves the breakdown of glucose (a six-carbon sugar) in the presence of oxygen (O2) to produce carbon dioxide (CO2), water (H2O), and energy.
The energy released during respiration is stored in molecules of adenosine triphosphate (ATP) which then powers various activities within the cell.

Respiration occurs in four main stages: glycolysis, the link reaction, the Krebs cycle, and oxidative phosphorylation.
Glycolysis, the first stage of respiration, occurs in the cytoplasm of the cell. It involves the break down of one molecule of glucose into two molecules of pyruvate.
This is followed by the link reaction, where pyruvate is converted into an acetyl group that is further processed in the Krebs Cycle.
In the Krebs cycle, one glucose molecule is fully oxidised to CO2. Each turn of the cycle produces ATP, NADH and FADH2 molecules.
The final stage is oxidative phosphorylation, where most of the ATP is produced. This process takes place across the inner mitochondrial membrane.

The primary purpose of respiration is to produce ATP. ATP drives many processes in cells, including muscle contraction, nerve impulse propagation, and chemical synthesis.
During respiration, the energy stored in glucose is transferred to ATP. The ATP then provides a readily available source of energy for numerous cellular processes.
The energy stored in ATP can be used immediately by the cell, avoiding the necessity for long-term energy storage in the form of glucose or fat.

Respiration is an efficient process. For each glucose molecule that is respired, up to 38 ATP molecules can be produced.
In eukaryotic cells, the mitochondria are the site of respiration, thus often referred to as the “powerhouse of the cell”.
Respiration, the process of converting food into usable energy, is fundamental to life. Without respiration, cells would not have the energy they need to function, and life as we know it would cease to exist.