2. Ground Rules of Metabolism

3.  Energy = capacity to do work  Potential Energy—stored energy in resting object  Kinetic Energy—energy of motion

4.  1 st Law of Thermodynamics: Energy cannot be created or destroyed  Converted from one form to another  2 nd Law of Thermodynamics: Energy flows from organized to disorganized forms  Concentrated energy tends to disperse spontaneously  Moves from useable to non-useable energy  Chemical bonds resist this direction of energy flow

5.  Entropy: Measure of randomness or disorder in a system  Organized energy = useable = less entropy  Disorganized = not useable = more entropy  Living things must maintain ongoing replacement of lost energy

6.  All chemical reactions within a cell or organism  Reactants  Products +=

7.  Anabolic  Building reactions (dehydration synthesis)  Endergonic—need energy  A + B + Energy = C  Usually not spontaneous  Catabolic  Breaking down reactions (hydrolysis)  Exergonic—release energy  C = A + B + Energy  Usually spontaneous

8.  Activation Energy—minimum energy that can get a reaction to run on it’s own.  Cells control energy input into reactions, therefore controlling timing & speed of reactions.

9.  Endergonic coupled with exergonic  Released energy from one fuels other C = A +B + Energy D + E + Energy = F

10.  Energy source for cells  Created by photosynthesis or in mitochondria

12.  Breaking down ATP releases energy  This powers cell fuctions  E.g. Active transport proteins

13.  Biological catalysts  Speed up chemical reactions  Don’t start reactions on their own  Reusable  Can catalyze in forward & reverse  Very specific!

14.  Substrate attaches to enzyme’s active site

15.  Lowers activation energy  Makes reactions faster & easier

16.  Concentration  Enzymes  Reactants  Products  Temperature  pH  Enzyme cofactors  vitamins

17.  Inhibition  Competitive—binds to site first or more strongly  Non-competitive—binds to different area, changing enzyme bonding area

18.  Feedback inhibition  Product of reaction binds to allosteric site  Shuts down reaction