Aerobic Cellular Respiration

Cellular respiration takes place in all living beings - plants, animals and human beings. For instance, the man gets his energy from the food he eats. Cellular respiration is a series of processes through which the energy stored in the food is harvested. Cellular respiration is of two types - anaerobic cellular respiration and aerobic cellular respiration. Aerobic cellular respiration would be discussed here.

What is Cellular Respiration?

Cellular respiration is a process that allows the cells to release the energy in glucose. The energy that is released from the glucose is used to produce ATP. The ATP supplies the energy needs of the cells. Therefore, cellular respiration is the process by which energy from glucose is transferred to ATP. Aerobic respiration plays a crucial role in the production of ATP.

What is ATP?

ATP is an abbreviation of Adenosine-5 - triphosphate. ATP is a multi-functional nucleotide which performs many important functions in a cell. ATP is a storehouse of energy and it provides energy to the cells for performing most of the energy-consuming activities. It also helps in regulating the biochemical pathways. The process by which ATP is produced is known as aerobic cellular respiration.

Aerobic Cellular Respiration

The process by which the energy from glucose is released in the presence of oxygen is called as aerobic cellular respiration. Aerobic cellular respiration takes place only if oxygen is available. For instance, if glucose were oxidized, the result would be energy, carbon dioxide and water. Take a look at the chemical formula given below.

C₆H₁₂O₆ + 6O₂ = 6CO₂ + 6H₂O + Energy (ATP)

In simple words, Glucose + Oxygen = Carbon dioxide + Water + Energy (ATP)

In brief, aerobic cellular respiration helps in release of maximum energy and also gets rid of carbon dioxide and excess water.

Three Stages of Aerobic Cellular Respiration

There are three stages of aerobic cellular respiration. They are

• Glycolysis - The process of Glycolysis takes place in the cytosol of the cell. In this stage of the aerobic cellular respiration, glucose is partially oxidized and is broken down into 3 carbon molecules of pyruvate. This process of glycolysis produces energy - 2 ATP molecules and 2 NADH (Nicotinamide Adenine Dinucleotide) molecules. Each NADH molecule carries 2 energy electrons. The cells later use these electrons.

• Krebs Cycle - This is the next stage of aerobic cellular respiratory. In Krebs cycle, pyruvate molecules are processed to release the energy that is stored between their molecular bonds. The energy is released in the form of ATP. This cycle is also known as the citric acid cycle.

• Electron Transport Chain - This is the final stage of aerobic cellular respiratory. During glycolysis and the Krebs Cycle, entire energy was not released from the glucose. In this stage of aerobic respiration, remaining energy from the glucose will be released by the electron transport chain. The network of electrons carrying proteins to the inner membrane of the cell is known as electron transport chain. Eventually, in this stage the electrons along with the protons will be added to oxygen. When electrons and protons are added to oxygen, it produces water and not ATP (energy). Actually, ATP is produced when the protons are moved across the cell membrane. This is known as chemiosis.

A point worth mentioning here is, while glycolysis takes place in the cytoplasm of the cell, the Krebs Cycle and electron transport takes place in the mitochondria of the cell. Oxygen plays a major role in aerobic cellular respiration because it is a great electron acceptor. It plays an active role in preventing the electrons from building up in the electron transport system.