 Metabolism  Totality of an organism’s chemical processes  Catabolic pathways (release energy)  Breakdown  Respiration  Anabolic pathway  Build up  Photosynthesis Metabolism, Energy, & Life

 Energy  Capacity to do work or cause change  Kinetic energy (energy of motion)  Potential energy  capacity of matter to cause change as a consequence of its location or arrangement.  Chemical energy  A form of potential energy that is available for release in chemical reactions. Metabolism, Energy, & Life

 Free energy (  G)  The portion of a system’s energy that can perform work when temperature is uniform throughout the system.  Energy available for work.  Exergonic reactions  Negative  G  Endergonic reactions  Positive  G Metabolism, Energy, & Life

 ATP  Adenosine triphosphate  Powers cellular work by coupling exergonic reactions to endergonic reactions.  ATP Cycle Metabolism, Energy, & Life ATP ADP + P i Energy from catabolism Energy for Cellular work

 Speed up the rate of a reaction.  Unchanged by the reaction.  Lower the Activation Energy required for the reaction to go forward.  Do not change the ∆G for reaction.  Substrate specific  Active site compatible to substrate  Forms enzyme-substrate complex  Induced fit model Enzymes Biological Catalysts

 Temperature and pH  Speed of an enzyme-catalyzed reaction may increase with rising temperature or pH up to the point at which increase thermal agitation or acidic/basic conditions begins to disrupt the weak bonds and interactions that stabilize protein shape.  Cofactors  Small molecules that bind either permanently or reversibly with enzymes and are necessary for enzyme function  Inorganic metal ions or organic coenzymes  Most vitamins are coenzymes or precursors of coenzymes.  Each enzyme has optimal conditions. Effects of Local Conditions on Enzyme Activity

 Competitive inhibitors  Compete for the active site.  Reversible  Increasing the concentration of substrate  Noncompetitive inhibitors  Do not directly compete with the substrate at the active site.  Bind to another part of the enzyme  Change in shape, altering the active site.  nonnreversible  Pesticide DDT; Many antibiotics Enzymes Inhibitors

 Allosteric Regulation  Regulatory molecules that change an enzyme’s shape and function by binding to an allosteric site.  Allosteric site  A specific receptor site on some part of the enzyme molecule, separate from the active site.  Effect:  Inhibition or stimulation of enzyme active Control of Metabolism

 Allosteric Regulation  Allosteric activator  Allosteric inhibitor  Feedback Inhibition Control of Metabolism