{"id":141,"date":"2017-09-04T05:05:50","date_gmt":"2017-09-04T05:05:50","guid":{"rendered":"http:\/\/americanboard.org\/Subjects\/general-science\/?page_id=141"},"modified":"2017-09-22T14:03:50","modified_gmt":"2017-09-22T14:03:50","slug":"cellular-energetics","status":"publish","type":"page","link":"https:\/\/americanboard.org\/Subjects\/general-science\/cellular-energetics\/","title":{"rendered":"Cellular Energetics"},"content":{"rendered":"
\n
\u2b05 Previous Lesson<\/a>\u00a0Workshop Index<\/a>\u00a0Next Lesson \u27a1<\/a><\/div>\n

<\/p>\n

Cellular Energetics<\/h1>\n
\n

Energetic Cells<\/h3>\n

You have read that cells get their energy from ATP (adenosine triphosphate). But what is ATP and where does it come from? ATP is the molecule of choice for energy transfer in all cells. ATP stores the energy that is used in cellular processes in the high-energy chemical bonds between its three phosphates. The breakdown of ATP breaks the phosphate bonds, releasing energy and making it available to the cell. The formula for this reaction is:<\/p>\n

ATP + H2<\/sub>O \u2192 ADP + Pi<\/sub> + energy<\/p>\n

Where Pi<\/sub> is inorganic phosphate. Often, the breakdown of ATP does not release inorganic phosphate, but instead transfers it, with the aid of an enzyme, to another molecule. This process is called phosphorylation. Thus, the phosphorylation of ADP creates ATP. Getting ATP from glucose is a multi-step process. The first step is glycolysis, which breaks down glucose, and the second step is respiration, which itself consists of two steps: the Krebs cycle and electron transport chain. Both oxidation (the loss of an electron) and reduction (the addition of an electron) may be used to create energy from glucose.<\/p>\n

Airless Energy: Glycolysis<\/h3>\n

Glycolysis, which occurs in the cell cytoplasm, is an anaerobic process that entails the splitting, or lysing, of glucose. There is a specific sequence of nine chemical reactions in glycolysis, each catalyzed by a particular enzyme. The overall purpose of glycolysis is to break down the carbon bonds in glucose and to use the released energy to produce fuel, or energy, for the cell (in the form of ATP):<\/p>\n

glucose + oxygen \u2192 carbon dioxide + water + energy<\/p>\n

C6<\/sub>H12<\/sub>O6<\/sub> + 6O2<\/sub> \u2192 6CO2<\/sub> + 6H2<\/sub>O + energy<\/p>\n

In glycolysis, a phosphate group is transferred from an ATP molecule to a glucose molecule. The glucose molecule then splits apart, and energy is produced as NAD (nicotinamide adenine dinucleotide, a hydrogen carrier). NAD is reduced to NADH (hydrogen having been obtained from PGAL, phosphoglyceraldehyde). Finally, molecules of ADP are phosphorylated to become ATP.<\/p>\n

\"Glycolysis<\/center><\/p>\n

Glycolysis is the lysing of glucose<\/p>\n

Glycolysis yields 2 ATP plus 2 molecules of pyruvic acid, so its electrons must be carried across the inner mitochondrial membrane. Once this occurs, more ATP molecules are produced. In total, glycolysis yields 8 ATP. The 9-step process (each product is the next reaction’s reactant) looks like this:<\/p>\n