Metabolism All the chemical reactions in an organism These reactions are controlled by enzymes Metabolic pathways are of two types a Catabolic pathways metabolic pathways which release energy by breaking down complex molecules to simpler compounds cellular respiration breaks down to glucose to carbon dioxide and water makes ATP b Anabolic pathways metabolic pathways which consume energy to build complex molecules from simpler ones photosynthesis makes glucose from carbon dioxide and water Vocabulary 1 kinetic energy energy of motion doing work 2 potential energy energy of position stored energy as in chemical bonds 3 exergonic reaction a reaction with a net loss of energy 4 endergonic reaction a reaction that gains energy 5 ATP the immediate source of energy within cells Cells break the phosphate bonds to release energy ATP is regenerated through cellular respiration 6 enzymes biological proteins that accelerate chemical reactions without being changes can be used over and over Enzymes reduce the energy required to break chemical bonds In a cell enzymes aid reactions that would by themselves move very slowly inside the cell Characteristics of Enzymes 1 are usually proteins 2 allows reactions to occur at cellular temperatures 3 speed up reactions but remains unchanged 4 are specific for a certain substrate 5 The substrate is the substance an enzyme acts on and makes more reactive The result is a product The substrate bonds to the enzyme s active site Starch substrate Enzyme amylase maltose the enzyme works only on a specific substrate Factors Affecting Enzymes Activity 1 Temperature most enzymes work well at 35 40 C High temperature will destroy and denature the enzyme 2 pH optimal pH for most enzymes is pH 6 8 Some enzymes work at pH extremes such as stomach enzymes that have a pH of 2 pH extremes can denature enzymes 3 High salt most enzymes cannot tolerate high salt concentrations as inorganic ions can interfere with ionic bonds within the enzyme 4 Competitive Inhibitors chemicals that resemble an enzyme s normal substrate and compete with it for the active site They block the active site from the substrate These inhibitors do not denature the enzyme They can be overcome by increasing substrate concentration 5 Noncompetitive Inhibitors These chemicals do not enter the enzyme s active site but bind to other parts of the enzyme and change the shape of the enzymes These inhibitors can denature the enzyme Some can act as metabolic poisons such as DDT formaldehyde
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