Energy & Enzymes Miss Napolitano & Mrs. Haas CP Biology

Metabolism& Energy  Metabolism : the total of all chemical reactions that take place within an organism  Energy : the capacity to do work  Kinetic energy : energy in motion  Potential energy : stored energy

Chemical Reactions Absorb or Release Energy  Exergonic reaction : releases free energy  Products contain less energy than the reactants  Energy exits  Example: cell respiration  Endergonic reaction : absorbs free energy  Products contain more energy than the reactants  Energy enters  Example: photosynthesis

Exergonic vs. Endergonic Ea = Activation Energy = the energy required to start the reaction Exergonic Endergonic

Catalysts  Catalyst : reduces the activation energy to speed up the chemical reaction  Enzyme : catalytic protein  End in - ase 1. Specific substrate binds to the active site on an enzyme 2. Enzyme reduces Ea 3. Reaction occurs, products are formed 4. Enzymes can be reused

Enzyme-Substrate Complex

Effect of Enzymes on Reaction Rate

External Factors can Affect Enzyme Activity  Factors that affect enzyme shape will affect its function  Ex: temperature, pH  Different enzymes have different optimal conditions

Enzyme Inhibitors  Inhibitors prevent an enzyme from catalyzing a reaction  Can block substances from entering the active site  Can bind to another part of the enzyme, causing the enzyme to change shape & become inactive