1)Bringing reactiong molecules into close proximity and correct oreintation

-Dun need so cheem..bring functional grps of substrates together can liao...

-Functional grps of substrate have to be in close proximity for reaction to occur

-Enzymes help to bind subtrates at active sites to ensure that the functional grps are placed at favourable positions

-Reaction can only occur when there is collision/close proximity of substrate molecules

-Higher substrate concentration, more frequent effective collisions between enzyme and substrates, faster reaction rates.


2)Stabilising transition state (enzyme-substrate complexes)

-Many reactions require formation of charged transition states(TS)

-No stabilizing agent,unstable TS goes back to reactant states

-Active site of enzymes act as flexible molecular template to allow substract to interact with a configuration resembling to the activated TS of molecule

-Catalytic residues have functional grps to enhance probability for transition state forms (R grps of catalytic residues can donate/accept electrons to stabilize substrates in the charged transition state to allow bond formation)

-Increases concentration of enzyme-substrate complexes, concentration of products increases.


3)Destabilise substrate

-Substrate is chemically and energetically stable on its own, chem reactions may not occur readily , formation of product is low.

-Enzymes bind to substrate, physically stress substrate to take on a more unstable configuration (Decrease bond angle, increase repulsion)

-Bonds in reactant molecules may break due to physical stress, strained substrate form transition state, can be stabilized by enzyme to allow product formation.