Glycolysis is a biological term used to describe reactions that extract energy from glucose by dividing it into two three-carbon molecules named pyruvates. It is an old metabolic pathway found in most living organisms (Chandel, 2021). The term glycolysis is derived from the root of two words, namely glycol, which stands for glucose, and lysis which means breaking down. Hence, when put together, the term glycolysis means glucose breakdown. Glycolysis is most distinguished in organisms that perform cellular respiration. However, the process does not require oxygen, and hence other anaerobic organisms possess such pathways.
The glycolysis process occurs in the cytoplasm of animals, plants, and microorganism cells involving at least six enzymes. The procedure can take place in two phases, the energy-requiring phase, and the energy-releasing phase. The glycolysis process comprises two types which include anaerobic and aerobic states. In aerobic conditions, pyruvate molecules enter the citric acidic cycles. Afterward, they undergo oxidative phosphorylation, which leads to the net production of two adenosine triphosphate (ATP) molecules. In anaerobic states, pyruvate converts to lactate through the process of anaerobic glycolysis. An example of glycolysis is that fully grown mammalian red cells are the only cells capable of glycolysis as they are their only ATP source. If the glycolysis is altered, the cells will die, leading the organism to experience difficulties in performing daily tasks.
Other researchers look at glycolysis as an inefficient process as much cellular energy remains in the two molecules of pyruvic acid created. This process can be compared to the reversal of photosynthesis as it is similar (Chandel, 2021). The process of glycolysis is vital to the cell as glucose is the primary fuel source for body tissues. Additionally, glucose metabolism is responsible for producing valuable byproducts that are useful in other metabolic pathways like the synthesis of fatty and amino acids.
Glycolysis is responsible for transforming glucose into several molecules of pyruvic acid. Additionally, this process is responsible for producing thousands of molecules in no time (Chandel, 2021). Although the process is vital, it has a disadvantage which is producing minimal energy. During the glycolysis process, one glucose molecule is divided into two pyruvate molecules; hence using two ATP means producing 4 ATP and two nicotinamide adenine dinucleotides (NAD) + hydrogen (H) (NADH)molecules.
Glycolysis happens in ten primary steps, including hexokinase, where D-glucose is converted into glucose-6-phosphate (G6P). Phosphoglucose isomerase is the second step where G6P is rearranged into fructose 6-phosphate (F6P). In phosphofructokinase, magnesium is used as a cofactor in altering F6P into fructose 1, 6-biphosphate. Aldolase is the enzyme that splits fructose 1, 6-biphosphate into two sugars: glyceraldehyde 3-phosphate and dihydroxyacetone phosphate isomers of one. Triosephosphate isomerase rapidly interconverts the molecules dihydroxyacetone phosphate and glyceraldehyde 3- phosphate while removing glyceraldehyde phosphate or is used in the next step. Glyceraldehyde-3-phosphate dehydrogenase adds an inorganic phosphate while dehydrogenating glyceraldehyde 3-phosphate produces 1,3-bisphosphoglycerate. Phosphoglycerate kinase is responsible for transferring a phosphate group from 1, 3-bisphosphoglycerate to Adenosine diphosphate (ADP) to create 3-phosphoglycerate. Phosphoglycerate mutase is responsible for relocating the P from a 3rd carbon to becoming the 2nd carbon to create 2-phosphoglycerate. Enolase enzyme removes the mole of water from 2-phosphoglycerate to form phosphoenolpyruvic acid (PEP). Lastly, we have pyruvate kinase that transfers the P from PEP to ADP after ATP and pyruvic acid.
When glycolysis is interrupted, cells lose their aptitude to uphold their sodium-potassium pumps, and hence, they die. Moreover, the last step of glycolysis will not occur if pyruvate kinase is not available in sufficient quantities. In glycolysis, there are three irreversible steps, including phosphofructokinase, hexokinase, and pyruvate kinase, hence the need to bypass some reactions for glucogenesis. Glucogenesis and glycolysis are different in that glycolysis is a catabolic process of metabolism while glucogenesis is an anabolic process.
Reference
Chandel, N. S. (2021). Glycolysis. Cold Spring Harbor Perspectives in Biology, 13(5). Web.