The equation C6H12O6 + 6O2 --> 6CO2 + H2O + energy depicts the process of cellular respiration. This is a process in which living organisms combine food (glucose) with oxygen into energy while producing carbon dioxide and water as waste products. Since organisms can't use the energy from food directly, cellular respiration is necessary to convert the energy into a form they can use known as adenosine triphosphate (ATP).
Stage 1 of Cellular Respiration: Glycolysis
The first stage of cellular respiration is known as glycolysis or glucose splitting. Enzymes split glucose into two molecules of pyruvate. Two molecules of ATP are needed to perform glycolysis, but the process produces four molecules of ATP. That means that there is a net gain of two ATP molecules. It also produces energy-carrying molecules that are needed in later steps of the cellular respiration process.
Stage 2 of Cellular Respiration: The Krebs Cycle
The Krebs Cycle is also known as the citric acid cycle because it forms citric acid. The series of reactions that take place in the Krebs Cycle release energy and produce carbon dioxide as a waste product. Glucose is completely broken down, and all of the energy is stored in the bonds of four ATP molecules, 10 nicotinamide adenine dinucleotide (NADH( molecules, and two flavin adenine dinucleotide (FADH2) molecules.
Stage 3 of Cellular Respiration: Electron Transport
In the final stage of cellular respiration, the high-energy electrons from NADH and FADH2 move along the electron transport chains. Some of this energy is used to pump hydrogen ions across the inner membrane of the mitochondrion from the matrix into the intermembrane space. They flow back into the matrix to form ATP synthase, which produces ATP. This process can only occur in the presence of oxygen. The hydrogen ions that pass through the electron transport chain combine with oxygen to form water.
The final stage of cellular respiration produces the most ATP. While two molecules of ATP are produced in each of the first two stages, the final stage produces as many as 34 more molecules of ATP. That's just from a single molecule of glucose. Not all energy produced from this process is in the form of ATP as much of the energy is released in the form of heat.
Aerobic vs. Anaerobic Respiration
Aerobic respiration occurs in the presence of oxygen, and anaerobic respiration does not rely on oxygen to take place. Most cellular respiration processes require oxygen. Glycolysis is the only stage that doesn't need oxygen to take place. When no oxygen is present, organisms break down their food in a process known as fermentation.
Role of Mitochondria
The mitochondria are known as the powerhouse of a cell because this is where cells produce energy. The mitochondria are made up of rod-shaped compartments that house the enzymes needed to break down food. Organisms can have thousands of mitochondria in each cell that are all working together to produce the energy necessary to carry out life processes.