Glycolysis

Cellular respiration is the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. Oxidation of organic materialЎЄin a bonfire, for exampleЎЄis an exothermic reaction that releases a large amount of energy rather quickly. The equation for the oxidation of glucose is:

C6H12O6 + 6O2 Ўъ 6CO2 + 6H2O + Energy released

Glycolysis is a metabolic pathway that is found in all living organisms and does not require oxygen. The process converts one molecule of glucose into two molecules of pyruvate, and makes energy in the form of two molecules of ATP. Glycolysis takes place in the cytoplasm of the cell. The overall reaction can be expressed this way:

Glucose + 2 NAD+ + 2 ATP + 2 Pi Ўъ 2 NADH + 2 pyruvate + 4 ATP + 2 H2O + 4 H+

The individual steps of the conversion of glucose into pyruvate are (in brief):

A glucose molecule from the hydrolysis of starch or glycogen is phosphorylated using one ATP molecule to give glucose-6-phosphate.

The glucose-6-phosphate is converted to fructose-6-phosphate by isomerisation.

Fructose-6-phosphate is again phosphorylated to give fructose-1,6-diphosphate with the use of another ATP molecule.

Next, the fructose-1,6-diphosphate is then lysed into two molecules of 3-carbon sugar (dihydroxyacetone phosphate and glyceraldehyde-3-phosphate) which are interconvertible.

The 3-carbon sugars are dehydrogenated and inorganic phosphate is added to them, forming two molecules of 1,3 diphosphoglycerate.

The hydrogen is used to reduce two molecules of NAD, a hydrogen carrier, to give NADH+H+. NADH+H+ later proceeds to the mitochondria for use in the electron transport chain.

The two molecules of 1,3 diphosphoglycerate lose two phosphate groups to form two molecules of glycerate-3-phosphate (3-phosphoglycerate), converting two molecules of ADP to ATP.

The two molecules of glycerate-3-phosphate again lose phosphate forming two molecules of pyruvate, with the production of another two ATP molecules (for a net gain of 2 ATP).

Aerobic respiration (Cellular Respiration)

Aerobic respiration requires oxygen in order to generate energy. It is the preferred method of pyruvate breakdown. As molecules of pyruvate travel into a mitochondrion entering the Krebs cycle. In this process it is broken down producing energy in the form of ATP (which travels to the cell), NADH and FADH2 which travel to the electron transport chain. In this process, an electron is transferred from an energy-rich atom (such as a carbon atom in an organic molecule) to an oxygen atom, via an electron transport chain. Oxygen serves as the "terminal electron acceptor" in the electron transport chain. In the process, it yields 36 ATP molecules via the diffusion of hydrogen atoms through an ATP synthase, as well as carbon dioxide and water. This makes for a total gain of 38 ATP molecules during cellular respiration under optimal conditions; however, such conditions are generally not realized due to such losses as the cost of moving pyruvate into mitochondria. This takes place in the mitochondria in eukaryotic cells, and at the cell membrane in prokaryotic cells.

Aerobic metabolism is rather more efficient than anaerobic metabolism. It actually starts off with the Glycolysis process of anaerobic metabolism, and then continues with the krebs cycle and oxydative phosphorylation.

Aerobic respiration (Cellular Respiration)

Aerobic respiration requires oxygen in order to generate energy. It is the preferred method of pyruvate breakdown. As molecules of pyruvate travel into a mitochondrion entering the Krebs cycle. In this process it is broken down producing energy in the form of ATP (which travels to the cell), NADH and FADH2 which travel to the electron transport chain. In this process, an electron is transferred from an energy-rich atom (such as a carbon atom in an organic molecule) to an oxygen atom, via an electron transport chain. Oxygen serves as the "terminal electron acceptor" in the electron transport chain. In the process, it yields 36 ATP molecules via the diffusion of hydrogen atoms through an ATP synthase, as well as carbon dioxide and water. This makes for a total gain of 38 ATP molecules during cellular respiration under optimal conditions; however, such conditions are generally not realized due to such losses as the cost of moving pyruvate into mitochondria. This takes place in the mitochondria in eukaryotic cells, and at the cell membrane in prokaryotic cells.

Aerobic metabolism