Respiration
Respiration is the cellular process in which reduced organic compounds are broken down into more oxydized, less energetic, compounds. In the process some of this liberated energy is used to form ATP. Aerobic respiration includes glycolysis, the Krebs cycle and the electron transport chain. A typical bioogy student should know where in the cell each occurs.
Plants respire. This is obvious with germinating grains where the generation of carbon dioxide and consumption of oxygen isn't masked by photosynthesis. Images here are of exercises using germinating grain to demonstrate plant rspiration. Also included are exercises demontrating alcoholic fermentation of yeast.
1. Aerobic respiration in germinating seeds, results in the formation of CO2, and the consumption of O2. Triphenyl Tetrazollium Chloride stains germinating grains red as it becomes reduced by the electron transport chain to form a red precipitate. The energy not converted to chemical bond energy of ATP is lost as heat as observed in lab.
2. Alcoholic fermentation - This is a form of anaerobic respiration. In the absence of O2, there is no receptor for the electrons passed down the electron transport chain, and the Krebs cycle cannot continue. ATP can still produced by glycolysis through the breakdown of glucose into two pyruvates, generating a net return of two ATPs and two NADH+'s. Glycolisis requres NAD. NAD is regenerated from NADH+ in a reaction converting pyruvate into ethanol and CO2, and NADH+ into NAD.
