Glycolysis

Glycolysis Glycolysis = (Glyco = sweet, sugar; lysis = to split); Glycolysis is anaerobic cellular respiration that involves the conversion of one glucose molecule into two pyruvate molecules and two molecules of water. The energy for initiation of glycolysis requires two ATP molecules. At the conclusion of glycolysis, four ADP molecules have been phosphorylated to produce four molecules of ATP. Thus, the net gain is two molecules of ATP. The metabolic pathway makes use of NAD+, an electron carrier. During glycolysis two NAD+ molecules are reduced to NADH. Pyruvate which is the end product of glycolysis, may then either enter the Krebs Cycle or a fermentation pathway. Depending the type of fermentation that occurs, the certain by products will be produced. Glycolysis is a catabolic pathway that occurs in the cytoplasm. During glycolysis, glucose, a six carbon-sugar, is split into two molecules of pyruvate (three-carbon sugars.) Glycolysis can occur with (aerobic respiration) or without (anaerobic respiration) oxygen. 2 ATP molecules are invested for each glucose molecule to split, and once two molecules of pyruvate is oxidized, 4 ATP and 2 NADH are produced. For each glucose molecule entering glycolysis a net gain of two ATP is produced by substrate-level phosphorylation. Two moleules of NAD+ are reduced to NADH (NADH is later used for ETC)No CO2 is produced during glycolysis. Substrate-level phosphorylation=a process that produces a small amount of ATP during glycolysis and the krebs cycle. During this process, the enzyme kinase transfers a phosphate from a substrate directly to ATP. Oxidative Phosphorylation= The way most ATP is produced during aerobic respiration—chemiosmosis. Produces ATP by using energy derived from the redox reactions of the ETC. Aerobic = (Aer = air; bios = life); existing in the presence of oxygen Pyruvate is oxidized further by substrate-level phosphorylation and by oxidative phosphorylation and more ATP is made as NADH passes electrons to the electron transport chain. NAD+ is regenerated in the process. Occurs in the mitochondria, requires the presence of oxygen, consists of krebs cycle and ETC. Occurs after the anaerobic respiration phase and produces 36 ATP molecules. Anaerobic = (An = without; aer = air); existing in the absence of free oxygen A catabolic process that produces a small of energy in the absence of oxygen. Begins with glycolysis and produces 2 molecules of pyruvate and then alcohol or latic acid. Coverts NADH to NAD+ by electrons to pyruvate.

1.Alcohol fermentation: Pyruvate is converted to ethanol in two steps: a. Pyruvate loses carbon dioxide and is converted to the two-carbon compound acetaldehyde. b. NADH is oxidized to NAD+ and acetaldehyde is reduced to ethanol. Many bacteria and yeast carry out alcohol fermentation under anaerobic conditions. 2.Lactic acid fermentation: NADH is oxidized to NAD+ and pyruvate is reduced to lactate. When oxygen is scarce, human muscle cells switch from aerobic respiration to lactic acid fermentation. Lactate accumulates, but it is gradually carried to the liver where it is converted back to pyruvate when oxygen becomes available.