2.  Spontaneous chemical reactions occur without a need for outside energy but may be very slow  Free energy: Δ G  Catalyst : a chemical agent that speeds up a reaction without being consumed by the reaction  Enzyme: a catalytic protein

3.  Every chemical reaction between molecules involves bond breaking and bond forming  Free energy of activation, or activation energy (E A ): initial investment of energy to start the reaction  Transition state: the summit where the reactants are in an unstable condition AB + CD AC + BD (SPONTANEOUS EXERGONIC)

4.  Enzymes are proteins which are biological catalysts  Speed up reactions by lowering the E A barrier  Heat denatures proteins and kills cells and it would speed up ALL reactions, so organisms need alternative- catalysis  Enzymes catalyze reactions by lowering the E A barrier, Enabling the reactant molecules to absorb enough energy to reach the transition state

5.  Substrate: the reactant an enzyme acts on  Enzyme-substrate complex: formed by an enzyme binding to its substrate Enzymes + Enzyme-substrate Enzyme + Product(s) Substrate(s) complex  Enzymes=proteins=macromolecules

6.  Active site: the restricted region of the enzyme molecule that binds to the substrate  a pocket on the surface of the protein  Induced fit: when the enzyme changes shape slightly so that the active site fits more snugly around the substance  Brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction

7.  In most enzymatic reactions, substrate binds to active site and is held there by weak interactions  Side chains (R groups) of a few of the amino acids that make up the active site catalyze the conversion of substrate to product  Product departs  Repeats  Most metabolic reactions are reversible and an enzyme can catalyze both forwards and backwards  The active site can lower an E A barrier by orienting substrates correctly, straining their bonds, providing a favorable microenvironment, and covalently bonding with a substrate

9.  Each enzyme has an optimal temperature and pH (6-8)  Cofactors: nonprotein helpers for catalytic activity required by many enzymes  coenzyme: if the cofactor is an organic molecule http://www.youtube.com/watch?v=5eBzLgleVL8

10.  Inhibitors reduce enzyme function  If done by covalent bonds the effects are irreversible.  Most are weaker bonds making them reversible  Competitive inhibitor: binds to active site, reduces productivity of enzymes by blocking substrates from entering active sites - can be overcome increase [ ] of the substrate  Noncompetitive inhibitor: impede reactions by binding to different site on enzyme

12.  Allosteric regulation: any case where a protein’s function at one site is affected by the binding of a regulatory molecule to a separate site - results in either inhibition or stimulation of activity  Cooperativity: mechanism that amplifies the response of enzymes to substrates  Feedback inhibition: a metabolic pathway is switched off by the inhibitory binding of its end product to an enzyme that acts early in the pathway  Ex: thermostat

14.  Some enzymes are grouped into complexes  Some are transported into membranes  Others are contained inside organelles  Metabolism (intersecting set of chemical pathways characteristic of life)= choreographed interplay of thousands of different kinds of cellular molecules http://www.youtube.com/watch?v=2N-ydg4J4tA http://www.youtube.com/watch?v=M5bftq-W2aY

15.  http://www.uic.edu/classes/bios/bios100/lec turesf04am/lect04.htm http://www.uic.edu/classes/bios/bios100/lec turesf04am/lect04.htm  http://www.youtube.com/watch?v=5eBzLgle VL8 http://www.youtube.com/watch?v=5eBzLgle VL8  http://www.youtube.com/watch?v=2N- ydg4J4tA http://www.youtube.com/watch?v=2N- ydg4J4tA  http://courses.washington.edu/conj/protein/ proregulate.htm http://courses.washington.edu/conj/protein/ proregulate.htm  http://bio1152.nicerweb.com/Locked/media/ ch08/ http://bio1152.nicerweb.com/Locked/media/ ch08/