Glucose cannot be used as directly by cell as a source of energy so cells use ATP as their immediate source of energy. * This conversion of glucose into ATP takes place during cellular respiration and there are 2 different forms of cellular respiration depending upon whether oxygen is available or not * Aerobic respiration requires oxygen and produces CO2, water and lots of ATP. * Aerobic has 4 stages:
1) Glycolysis – the splitting of the 6-carbon glucose molecule into 2 3-carbon molecule pyruvate molecules. 2) Link reaction – the conversion of the 3-carbon pyruvate molecule into CO2 and a 2-carbon molecule called acetylcoenzyme A. 3) Krebs cycle – the introduction of acetylcoenzyme A into a cycle of oxidation-reduction reactions that yield some ATP and a large number of electrons. 4) Electron Transport Chain – the use of the electrons produced in Krebs to synthesis ATP with water produced as a by-product. Glycolysis is the initial stage of both aerobic and anaerobic respiration * It occurs in the cytoplasm of all living cells and is the process by which a hexose sugar, usually glucose, is split into two molecules of pyruvate * Although there a number of smaller enzyme-controlled reactions in glycolysis, these can be grouped into 4 stages: 1) Activation of glucose by phosphorylation. Before it can be split into two, glucose must first be made more reactive by the addition of 2 phosphate molecules (phosphorylation). The phosphate molecules come from the hydrolysis of 2 ATP molecules to ADP. This provides the energy to activate glucose (lowers the activation energy) 2) Splitting of the phosphorylated glucose. Each glucose molecule is split into 2 3-carbon molecules known as triose phosphate 3) Oxidation of triose phosphate. Hydrogen is removed from each of the 2 triose phosphate molecules and transferred to a hydrogen-carrier molecule known as NAD to form reduced NAD 4) The production of ATP. Enzyme-controlled...
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