Enzymes
Biochemical reactions
Reactions convert substrates into products
Reactions produce changes in free energy
Reactions are reversible
1st law of thermodynamics-energy cannot be created or destroyed it can only change from
one form to another
Total amount of energy remains constant
Endergonic reaction-products contain more energy than the reactants=energy in
Exergonic reaction-products contain less energy than the reactants and excess energy is
released
Before new chemical bonds can form existing bonds must be broken which requires energy
This is called activation energy
The role of catalysts in metabolism
Chemical reactions are too slow on their own to sustain life
Catalysts speed up reactions
Activation energies aren’t constant
Catalysts lower the amount of activation energy required to begin reaction
Enzymes
Most enzymes are proteins, some are RNA
Shape of enzyme stabilises temporary association between substrates
E.g., carbonic anhydrase- 200 molecules per hour without enzyme and 600000 with enzyme
per second
Ribozyme -RNA enzyme, similar to protein enzymes
Naming enzymes
End in ase
Name indicates function n
Protases-break down protein
Lipases break down lipids
Synthases build molecules
Enzyme structure
Enzymes are mostly proteins
Have an active site that binds to substrate
Lock and key model sometimes used but better model is induced fit
Ribozyme is exception
Enzymes specific to substrate
Hermann Fischer-lock and key model
Daniel Koshland-induced fit model
Active site
Biochemical reactions
Reactions convert substrates into products
Reactions produce changes in free energy
Reactions are reversible
1st law of thermodynamics-energy cannot be created or destroyed it can only change from
one form to another
Total amount of energy remains constant
Endergonic reaction-products contain more energy than the reactants=energy in
Exergonic reaction-products contain less energy than the reactants and excess energy is
released
Before new chemical bonds can form existing bonds must be broken which requires energy
This is called activation energy
The role of catalysts in metabolism
Chemical reactions are too slow on their own to sustain life
Catalysts speed up reactions
Activation energies aren’t constant
Catalysts lower the amount of activation energy required to begin reaction
Enzymes
Most enzymes are proteins, some are RNA
Shape of enzyme stabilises temporary association between substrates
E.g., carbonic anhydrase- 200 molecules per hour without enzyme and 600000 with enzyme
per second
Ribozyme -RNA enzyme, similar to protein enzymes
Naming enzymes
End in ase
Name indicates function n
Protases-break down protein
Lipases break down lipids
Synthases build molecules
Enzyme structure
Enzymes are mostly proteins
Have an active site that binds to substrate
Lock and key model sometimes used but better model is induced fit
Ribozyme is exception
Enzymes specific to substrate
Hermann Fischer-lock and key model
Daniel Koshland-induced fit model
Active site
