Ground Rules of Metabolism

I.  Metabolism = All controlled, enzyme-mediated chemical reactions 
                 by which cells acquire and use energy.

II.  Energy = Capacity to do work.

     A.  Work = Distance X Force

     B.  Cells synthesize, store, degrade, and eliminate substances
         that contribute to growth, survival, and reproduction.

     C.  First Law of Thermodynamics = Energy is neither created or 
         destroyed, only converted to other forms.

     D.  Second Law of Thermodynamics 

         = Conversion of energy from one source to another source 
           is never 100% efficient, some energy is always lost as 
           heat.
         
        = No process can take place which results in a net decrease 
          in the entropy of the universe.

        1.  Entropy = Degree of randomness or disorder in a system.
            

     E.  Do living organisms violate the Second Law of            
         Thermodynamics?

          1.  Sun
          2.  Earth
          3.  Plants
          4.  Chloroplasts (Photosynthesis)
          5.  Animals/Plants (Respiration)


III.  Chemical Reactions

     A.  Exergonic

     B.  Endergonic

     C.  Reversible

     D.  Chemical Equilibrium

     E.  Redox Reactions

          1.  Oxidation = atom/molecule gives up electron

          2.  Reduction = atom/ molecule receives electron

IV.  Enzymes = Organic catalysts 

     A. Characteristics

          1.  Accelerates
          2.  Recycled
          3.  Reversible
          4.  Selective

     B. Induced-fit Model (Koshland)

          1. Substrate(s) almost fits active site
          2. Substrate(s) induces strain in enzyme to create the
             "Transition State".
          3. Substrate(s) in transition state react spontaneously
             to produce products.

     C.  Enzyme Activity is dependent on 3D shape of Active Site

          1. Physical constraints

               a. Temperature
               b. pH

          2. Organic control

               a. Synthesis
               b. Degradation
               c. Feed back inhibition

                    1. Competitive
                    2. Noncompetitive

               d. Cofactors

                    1. Coenzymes (NAD+, FAD+, NADP+)
                    2. Metal Ions (Fe++)

V.  Metabolic Pathway = orderly sequence of events of reactions   
    with specific enzymes acting at each step.

     A.  Linear vs. Cyclic

     B.  Biosynthetic vs. Degrative

VI.  Electron Transport Systems = organized sequence of enzymes and 
                                  coenzymes.

     A.  In membranes
     
     B.  Electrons transferred between substrates

     C.  Energy released during electron transfer can do work

VII. ATP = the currency of metabolism or energy exchange