0.25 Bis2a 07.1 glycolysis  (Page 2/12)

In addition to the 2 molecules of ATP and NADH the cells gain a series of small intermediates or precursors that are necessary for the construction of monomers which in turn are used to build polymers. These precursors include: Glucose-6-phosphate, Fructose-6-phosphate, Triose-phosphate, 3-Phosphoglycerate, Phosphoenolpyruvate, and Pyruvate . These substrates are the building blocks to form monomers that lead to a variety of biopolymers including including proteins (monomer: amino acids) and polysaccharides.

The net result of glycolysis: 2 pyruvates, 2 NADH and 2 ATP. the other important point is that this is an anaerobic    process. There is no requirement for molecular oxygen in glycolysis. This process occurs in the cytosol or cytoplasm of cells. For a short (3 minute) overview YouTube video of glycolysis click here .

Glycolysis: the oxidation of glucose to pyruvate

Glycolysis is the metabolic process of breaking down or oxidizing hexoses, or six carbon sugars, to two molecules of pyruvate, a three carbon keto acid. The importance of glycolysis is really two fold, first is to generate small carbon compounds that the cell can use as building blocks construct other cellular components. Secondly, many cells, including mammals generate energy in form of ATP from glycolysis. Whhile not all cells generate energy from glycolysis, nearly all living organisms carry out glycolysis as part of their metabolism. The process does not use oxygen and is therefore anaerobic    . Glycolysis takes place in the cytoplasm of bacteral, archeal and eukaryotic cells. Remember that most biological processes are freely reversible, depending upon the needs of the cell. The reverse set of reactions to glycolysis, that is, the process of taking two molecules of pyruvate and reducing them to form one molecule of glucose is called gluconeogenesis . The balance between these two process keeps the flux of carbon (hexoses) sensitive to the needs of the cell.

While glycolysis begins with glucose being activated with the addition of a phosphate from ATP, many different types of hexoses (six carbon sugars) and polysaccharides (polymers of sugars) can feed into glycolysis at the point of glucose or glucose-6-phosphate. Many different hexoses, such as Galactose or Mannose, can be converted to glucose by a hexose isomerase , an enzyme that can rearrange the hydroxyl groups on the hexose and form glucose. Disaccharides (such as lactose, maltose or sucrose), trisaccharides (such as maltose triose) and polysaccharides (longer sugar polymers such as starch or glycogen) can be degraded by hydrolysis reactions to the monomers which can then be converted to glucose and enter glycolysis. The importance of glycolysis and gluconeogenesis, and along with the TCA cycle is central to all cells for the production of compounds necessary to build the monomers for biopolymers. As a result, these pathways has been given the common name of " Central Metabolism ".

Glycolysis begins with the six carbon ring-shaped structure of a single glucose molecule and ends with two molecules of a three-carbon sugar called pyruvate    . Glycolysis consists of two distinct phases. The first part of the glycolysis pathway traps the glucose molecule in the cell and uses energy to modify it so that the six-carbon sugar molecule can be split evenly into the two three-carbon molecules. The second part of glycolysis extracts energy from the molecules and stores it in the form of ATP and NADH, the reduced form of NAD ⁺ .