AP BIO Unit 2: Enzymes

AP BIO Unit 2: Enzymes

1. The Energy of Life

   • metabolic pathways
     • metabolism: all of the chemical reactions that take place within an organism
   • forms of energy
     • kinetic
       • energy not in motion
       • thermal energy: heat
         • the combination of all the movement of the particles in a substance
         • the energy most difficult to use for doing work
     • potential
       • the energy of motion
       • chemical energy
         • the potential energy stored within the bonds (chemical makeup) of a substance-- the potential of energy available for release in a chemical reaction
   • The laws of energy transformation
     • 1st law of thermodynamics
       • energy cannot be created or destroyed, only transferred or transformed
     • 2nd law of thermodynamics
       • every energy transfer or transformation increases the entropy of the universe
   • biological order and disorder
     • even when the entropy of a certain system is reduced, the overall energy of the universe may be increased due to the production of heat energy

2. the free energy changes of a reaction tell us whether or not it occurs spontaneously

   • free energy change (ΔG), stability, and equilibrium
     • ΔG= energy of reactants - energy of products
       • reactions with a negative ΔG are spontaneous, exergonic
       • reactions with a positive ΔG are non-spontaneous, endergonic
     • things are naturally moving towards equilibrium?
   • free energy and metabolism

3. ATP powers cellular work by coupling exergonic reactions to endergonic reactions

   • the structure and hydrolysis of atp
     • ATP= adenosine TRI phosphate
       • tends to lose one phosphate group, becomes ADP: adenosine DIphosphate
         • phosphate groups tend to detach because of their negative charge (negatives next to each other--> like charges repel)
   • how the hydrolysis of ATP performs work
   • the regeneration of ATP
     • from ADP?

4. Enzymes speed up metabolic reactions by lowering energy barriers

   • the activation energy barrier
     • EsubA: activation energy
     • the input energy required for an endergonic reaction to begin
   • how enzymes speed up reactions
   • substrate specificity of enzymes
     • structure of enzymes specific to fit enzymes: proteins (3, 4 structures)
       • some enzymes are nucleic acids
     • induced fit
       • when a substrate enters an enzyme's active site, the enzyme's structure changes slightly to grip more tightly around the substrate
     • substrate: what is catalyzed by the enzyme
     • enzyme: a biological catalyst
   • catalysis in an enzyme's active site
     • substrate enters an enzyme's active site, it catalyzed
   • effects of local conditions on enzyme activity
     • effects of temperature and pH
       • enzyme has an optimal pH and temp where catalysis is most efficient
         • temp
           • temp: below optimal point, as temp increases efficiency increases...
             • temp= average heat energy, heat energy= average motion of particles in a substance... more temp=more motion of molecules= substrates will enter enzymes faster
           • past optimal point, as temp increases efficiency decreases
             • too much heat (too much motion of particles) can cause protein denaturation-- weak bonds holding together a protein's 3°/4° structures (what creates its function) are broken
         • pH
           • either more acidic or more basic than optimal point= less efficient
             • can cause protein denaturation... 
             • ex: enzymes in stomach made specifically to function at pH of 2 (pH of stomach acid)... other enzymes would denature in that state
     • cofactors
       • molecules needed for/that aid in an enzyme's catalysis
       • conenzymes: organic (molecule) cofactors
     • enzyme inhibitors
       • needed for when enough of end product has been catalyzed
       • competitive inhibitors
         • fit directly into an enzyme's active site, blocking substrates from doing so
       • noncompetitive inhibitors
         • fit into a site on the enzyme other than the active site, change the enzyme's structure so the enzyme will no longer fit
   • the evolution of enzymes

5. regulation of enzyme activity helps control metabolism

   • allosteric regulation of enzymes
     • can be both 
     • allosteric site
       • site on an enzyme where allosteric regulators attach-- not the active site
   • allosteric activators and inhibitors
     • feedback inhibition
   • specific localization of enzymes within the cell

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