enzymes Flashcards
what’s the functions of enzyme?
Digestion DNA synthesis Cell signalling Respiration Metabolism Cell movement & growth Cellular digestion Immunology Transport of CO2 Control of vascular tone Control of neuronal pathways ROS Etc…….
how are enzymes powerful and highly specific
Enzymes are specific in the reactions they catalyse and in their choice of reactants (substrate)
Enzymes normally catalyse just one reaction
Side reactions leading to harmful waste products are rare in enzyme catalysed reactions.
give some examples of Proteolytic enzymes (break down proteins)
Papain (found in papaya plants) will break any peptide bond- is used to tenderise meat
Trypsin (digestive enzyme) only splits bonds between lysine and arginine residues
Thrombin catalyses the hydrolysis or Arg- Gly only in a specific chain of residues
what is the transition state
Catalytic power comes from their binding substrates together in an orientation that promotes the formation of transition states
what happens when substrate binds to enzyme
When the substrate binds, the enzyme may stretch or distort a key bond and weaken it so that less activation energy is needed to break the bond at the start of the reaction
The shape of active sites differ wildly but they have 3 common features. what are they?
- The active site is a 3D cleft formed by groups that come from different parts of the amino acid sequence
- The active site takes up a small proportion of the enzyme.Create scaffolding and regulatory sites
- Substrates are bound to enzymes by multiple weak reactions.
The specificity of binding depends on :
on the precisely defined arrangement of atoms in an active site. And can be altered by a change in amino acid away from the binding site.
The R groups in the active site create charged regions that only appropriate chemical groups can bind to
models of enzymes
lock and key and induced fit
