Chapter 8.1, 8.2, 8.4, 8.5

 metabolism is the process of breaking down and creating molecules necessary for life ◦ each step in this process is driven by an enzyme which directs the speed of the reaction (enzymes are proteins!)  catabolic--breakdown molecules  cellular respiration  anabolic--build molecules  protein synthesis

 energy is the capacity to cause change ◦ kinetic (heat) vs. potential (chemical)  thermodynamics = energy transformations ◦ 1st law (matter cannot be created or destroyed, only change form) ◦ 2nd law (energy transfer increases the entropy of the universe)  spontaneous reactions vs. reactions that need energy

 free energy--identifies if a reaction requires energy to proceed ◦ higher free energy = unstable  does not require outside energy for the reaction to happen (spontaneous)  exergonic reaction (negative delta G)  does not imply that it happens fast! ◦ lower free energy = stable  requires outside energy for the reaction to proceed (nonspontaneous)  endergonic reaction (positive delta G)

 Lower energy barriers for the reaction to happen at an increased rate (catalyst); not used up during the reaction ◦ activation energy (energy required to get reaction going)  based on how difficult it is to break the chemical bonds ◦ speed up reactions that would occur anyway

 substrate (reactant an enzyme acts on) ◦ enzyme binds to substrate, forming enzyme- substrate complex ◦ each enzyme has a specific substrate (results from unique sequence of amino acids)  active site (region of enzyme where substrate binds) ◦ when this occurs, the shape of the enzyme changes which enhances the reaction

 Rate in which enzyme converts substrate to product is determined by... ◦ the initial concentration of the substrate (or enzyme)  more substrate molecules that are available the more frequently they access active site.  limited by the enzyme concentration (saturated when rate of reaction is determined by how often substrate can move into active site) ◦ general environmental factors  temperature, pH, and other chemicals  each enzyme has optimal environment depending on the organism and where it needs to work

 competitive inhibition ◦ reduce the productivity of enzymes by blocking substrate from entering active site ◦ overcome by increasing concentration of substrate  noncompetitive inhibition ◦ impede reactions by binding to another part of the enzyme, thus changing the shape of the active site and making it less effective ◦ **often pesticides, antibiotics, and toxins are inhibitors

 enzymes need to be told when and where to be active so only necessary reactions are occurring ◦ Allosteric regulation  protein function changed by binding of another molecule  has active (activator binds) and inactive (inhibitor binds) forms  “Chemical on/off switch” ◦ feedback inhibition  end product of reaction binds to enzyme causing inhibition, thus slowing the reaction down