Metabolic Pathways
A metabolic pathway is the sequence of biochemical reactions that occur within a single cell. Enzymes catalyze each step of the pathway. Metabolic pathways allow cells to obtain energy from food, and biosynthesize molecules they need. Most common metabolic pathways are glycolysis, glycogenesis and fatty acid syntheses. Other types include the Krebs cycle, electron transport chain and pentose-phosphate pathway. (3)
Glycolysis
Glycolysis produces energy by breaking down glucose in the body. The sugar molecule glucose is produced in the body and found in foods. Glycolysis is a process that occurs in every cell of the body. It is essential for life. The first step of glycolysis is to convert glucose into two molecules of Pyruvate. The enzyme glycolase catalyzes this step. The next step involves the conversion of pyruvate into acetyl CoA. The enzyme pyruvate-dehydrogenase catalyzes this step. The conversion of acetyl CoA into CO2 and water is the final step of glycolysis. The enzyme acetyl CoA carboxylase catalyzes this step.
Glycogenesis
Glycogenesis, or the process of creating glycogen (a complex carbohydrate), is a way to make this type of carbohydrate. The addition of water molecule to glucose converts it into glycogen. Insulin, released by the pancreas when blood glucose levels rise, regulates the process. Insulin makes cells take glucose out of the bloodstream and convert it to glycogen.
Fatty Acid Synthesis
Fatty acids, also known as essential fatty acids, are fats that are required for proper body functioning. The body can synthesize some fatty acid, but others must be obtained through food. Fatty acid synthesis is the process of synthesizing fat acids.
The body can synthesize two types of fatty acid: unsaturated and saturated. Saturated fats have no double bond, whereas unsaturated fats have one or multiple double bonds. Synthesizing saturated fatty acid is easier than synthesizing un-saturated fatty acid.
The Krebs cycle
The Krebs cycle produces energy within cells. The cycle was named for the scientist Hans Adolf Krebs, who first discovered it. The cycle begins with the breakdown and release of energy from glucose. This energy is then used to produce a molecule known as acetyl CoA (acetyl CoA). The acetyl CoA is then broken down in the Krebs cycle into water and carbon dioxide. This process releases energy that is then used to produce new molecules of Acetyl CoA. For every glucose molecule that is broken down, the Krebs cycle will complete four times. The cycle’s final products are water and carbon dioxide.
The electron Transport Chain
This is a group of proteins that are found within the inner membranes of mitochondria. These proteins transfer electrons from organic molecule to oxygen. This results in the production of adenosine Triphosphate (ATP), which is the primary source of energy for cells. Each complex contains multiple proteins. The complex I complex is the first complex that transfers electrons from NADH into ubiquinone. Complex II, or succinate dehydrogenase transfers electrons from fumarate to succinate. Complex III (also known as cytochrome c reducetase) transfers electrons from cytochrome c into oxygen. Complex IV (also known as cytochrome C oxidase), converts oxygen into water.
Pentose phosphate pathway
The pentose-phosphate pathway is an enzyme pathway that converts glucose to glucose-5-phosphate, and NADPH. The pentose phosphate pathway is a metabolic pathway that produces glucose-5-phosphate and NADPH from glucose. This pathway is used for energy production and biosynthesis of new molecules. The HMS is responsible for producing NADPH which is essential in cellular redox reaction. This pathway is found in the cytoplasm and is vital for the proper functioning of the cell.