Metabolism

• Sum of all of the enzyme-controlled chemical reactions that occur within a living organism, metabolic pathway is sequence of these reactions resulting in the formation of one substance (product) from a different one (substrate)
• Catabolic reaction: results in breakdown of organic molecules; most are exergonic (release of chemical energy) and often involve oxidation ( H^+ or e^- removal) or hydrolysis (adding H_2O) to break bonds
• Anabolic reactions: Results in the synthesis of small molecules to form larger ones, are endergonic (absorb chemical energy stored in new molecule), and often involve condensation (removal of H_2O)
• Metabolites are converted to products in a series of small reactions, not one big one, as large catabolic reactions create unfavourable conditions for life, substances can be partially broken down for raw materials, organic compounds are complex, so synthesis is impossible in one step with simple raw materials, and small steps in anabolic pathway control product production
• Oxidation: Breakdown using oxygen, but can also mean removal of electrons or hydrogen from the substance and Reduction: Addition of electrons to a substance; in metabolic pathway, can involve addition of hydrogen
• Oxidoreductases: Group of enzymes which catalyse oxidation-reduction (redox) reactions; common names include dehydrogenase, oxidase, reductase and catalase
• Hydrolases: Group of enzymes which catalyse hydrolysis reactions; examples: proteases, nucleases and phosphatases
• ATP (adenosine triphosphate): Central metabolism molecule, main product from both respirations, energy source for all cells and gives it up quickly when needed for a reaction
• ATP (adenosine triphosphate): Central metabolism molecule, main respiration product and energy source for all cells; remains here (can't move around body) and must be continuously produced, often called ‘universal energy carrier’ or ‘energy currency’, it provides phosphate groups for metabolic pathways and enzyme activation