8. Enzymes

Nota:

• A quarter of the genes in the human genome encodes enzymes
• Mediate the transformation of one form of energy to another

1. Catalytic power

   Nota:

   • They catalyze by stabilizing transition states
   1. Active site

      Nota:

      • The particular site the catalysis takes place on the enzyme
   2. Proteins

      Nota:

      • Nearly all know enzymes are proteins
      • capacity to specifically bind a very wide range of molecules
2. Specificity
3. Substrates

   Nota:

   • The very specific reactants enzymes choose to catalyze reactions with
4. Proteolytic enzymes

   Nota:

   • These enzymes catalyse proteolysis
   1. Proteolysis

      Nota:

      • The hydrolysis of a peptide bond
   2. Hydrolysis of an ester bond
5. Cofactors

   Nota:

   • Able to execute chemical reactions
   1. Holoenzyme

      Nota:

      • An enzyme with a cofactor
   2. Metals
   3. Coenzymes

      Nota:

      • Small organic molecules
      1. Prosthetic groups

         Nota:

         • Tightly bound coenzymes
      2. Cosubstrates

         Nota:

         • Loosely bound coenzymes. They are like substrates and products, they bind to the enzymes and are released from it.
6. Apoenzyme

   Nota:

   • An enzyme without a cofactor
7. Free energy (G)

   Nota:

   • A thermodynamic property, that is a measure of useful energy to the energy that is capable of doing work
   1. ΔG

      Nota:

      • The free energy difference, ΔG, between reactants and products Tells us whether the reaction will take place spontaneously 
      1. 1. Exergonix

         Nota:

         • A reaction that takes place spontaneously --> ΔG is negative 
      2. 2. Equilibrium

         Nota:

         • A system is at equilibrium and no net change can take place if ΔG is zero    
      3. 3. Endergonic

         Nota:

         • A reaction cannot take place spontanously if ΔG is positive ( An input is required to drive such a reaction)
      4. 4. Independent of the path

         Nota:

         • ΔG of a reaction depends only on the free energy of the products minus the free energy of the reactants. The ΔG of a reaction is independent of the path of the transformation. 
      5. 5. Provides no info about the rate

         Nota:

         • A negative ΔG indicates the a reaction CAN take place spontaneously, but doesn't specify whether it will proceed at a specifik rate
   2. Energy required

      Nota:

      • The energy required to initiate the conversion of reactants into products Tells us the rate of the reaction
      1. ΔG°

         Nota:

         • The standard free energy
         1. ΔG°'

            Nota:

            • The standard free energy change at pH 7
            1. Keq'

               Nota:

               • The equilibrium constant under standard conditions