glycolysis

• Glycolysis is the first step in cellular respiration, which converts glucose into pyruvate.
• There are ten steps to glycolysis, with some reactions occurring simultaneously or in parallel.
• Glucose enters glycolysis as a six-carbon sugar (glucose) and exits as three-carbon sugars (pyruvic acid).
• The net gain from glycolysis is two ATP molecules per glucose molecule.
• Glucose is converted to glucose-6-phosphate by hexokinase (reaction 1). This reaction requires energy from ATP and produces ADP.
• The glycolytic breakdown of glucose is the sole source of metabolic energy in somemammalian tissues and cell types (erythrocytes, renal medulla, brain, and sperm, for example).
• Many anaerobic microorganisms are entirely dependent on glycolysis.
• Glycolysis is the major pathway of glucose metabolism and occurs in the cytosol of all cells.
• Glycolysis can occur aerobically or anaerobically depending on whether oxygen is available. Aerobic glycolysis occurs in 2 steps. The first occurs in the cytosol and involves the conversion of glucose to pyruvate with resultant production of NADH. This process alone generates 2 molecules of ATP. If oxygen is available, then the free energy contained in NADH is further released via reoxidization of the mitochondrial electron chain

  However, when oxygen is in short supply, this NADH is reoxidized instead by reducing pyruvate to lactate.
• Aerobic and anaerobic glycolysis are two ways by which organisms break down glucose and convert it into pyruvate.The aim of the glycolysis process is to convert food into energy.
• The first difference between aerobic and anaerobic glycolysis is the absence or presence of oxygen. If oxygen is present, the process is termed as aerobic, if it is absent, then the process is anaerobic.
• The second difference involves by-products of the process. Aerobic glycolysis has carbon dioxide and water as by-products, while anaerobic glycolysis has different by-products in plants in animals: ethyl alcohol in plants, and lactic acid in animals.
• The human body utilizes both aerobic and anaerobic glycolysis during exercise. A balance of aerobic and anaerobic exercise is needed to achieve ideal body fitness.
• Phosphorylation of glucose to glucose-6-phosphate by hexokinase or glucokinase. (reaction 1). It is a spontaneous reaction.
• Isomerization: Glucose-6-Phosphate is converted to Fructose-6-Phosphate by phosphohexoseisomerase. (reaction2)
• Phosphorylation of Fructose 6-Phosphate to Fructose-1,6-Bisphosphate by phosphofructokinase-1. (reaction3)
• Cleavage of Fructose-1,6-Bisphoshate to Dihydroxyacetonephoshate and Glyceraldehyde-3-phosphate by aldolase. (reaction 4)
• Interconversion of the Triose Phosphates: Dihydroxyacetonephosphate to Glyceraldehyde-3-phosphate by triose phosphate isomerase. (reaction5)
•  Oxidation of Glyceraldehyde 3-Phosphate to 1,3-Bisphosphoglycerate by glyceraldehyde-3-dehydrogenase. (reaction 6) Oxidation and phosphorylation, yielding a high-energy mixed-acid anhydride
• Conversion of 3-Phosphoglycerate to 2-Phosphoglycerate is catalyzed by the enzyme phosphoglycerate mutase. (reaction 8).
• Conversion of 1,3-Bisphosphoglycerate to 3-Phosphoglycerate is catalyzed by the enzyme phosphoglycerate kinase. (reaction 7) Phosphoryl Transfer from 1,3-bisphosphoglycerate to ADP. Transfer of a high-energy phosphoryl group to ADP, yielding ATP
• Conversion of 2-Phosphoglycerate to Phosphoenolpyruvate is catalyzed by the enzyme enolase. Dehydration to an energy-rich enol ester (reaction9).
• Conversion of Phosphoenolpyruvate to pyruvate is catalyzed by pyruvate kinase. (reaction 10) Transfer of the Phosphoryl Group from Phosphoenolpyruvate to ADP. Transfer of a high-energy phosphoryl group to ADP, yielding ATP.