enzymes
enzyme theory
biological catalysts
globular proteins
specific to one substrate -> active site has a specific shape and chemistry which determines which substrate can bind
effect structure and function of organisms
intracellular
made an acts inside cell
e.g. catalysts
extracellular
made in cells, but are released into surroundings, so work outside of the cell
e.g. amylase, trypsin
lock and key theory
enzyme+substate -> enzyme substrate complex -> enzyme product complex -> enzyme+product
key words
active site and substrate are complementary in shape and specific, caused by the tertiary structure of the enzyme
induced fit
enzyme and substrate do not perfectly fit together
active site changes shapes slightly to fit the substrate
induced fit process
the substrate enters the active site of the enzyme
the enzyme clamps down around the substrate forming an induced fit
enzyme reaction - temperature
• increasing temp increases KE so more collisions between the active site and substrate with enough energy to react
• reaches optimum temp
• enzyme vibrate so much that bonds holding tertiary structure together begin to break and enzyme loses its shape
therefore it is denatured so substrate no longer fits active site
enzyme reaction - pH
• denaturing occurs at too high and too low pH
• h+ ions interact with the r groups affecting the ionic and hydrogen bonds in the tertiary structure
• at Extreme pH the h+ ions interfere with the bonds in the tertiary structure of the enzyme causing the shape to change so the active site nude longer fits to substrate so enzymes denature
enzyme reaction - enzyme conc
• increasing enzyme conc increase rate of reaction
• the endpoint remains the same, you will just get the product quicker
• better to compare initial rate -> substrators in excess
enzyme reaction - substrate conc
• endpoint will depend on the conc of substrate
• again it is better to measure initial rate and plot initial rate vs conc of substrate on graph
• initially increasing substrate conc, you get increasing initial rate
• eventually the substrate conc gets so high that the rate does not increase because all active sites are occupied and the enzyme cannot work faster
competitive inhibition
• molecule has a similar shape to substrate so we'll fit into the active site temporarily
• while inhibitor is in the active site, it prevents the substrate from binding to the active site
non-competitive inhibition
• binds to an allosteric site (from the active site) -> denatures enzyme
• the inhibitor binds to the allosteric site changing the active site shape so the substrate no longer fits
cofactors and coenzymes
transfer atoms or groups from one reaction to another to form part of the active site
cofactor
inorganic minerals e.g. iron, calcium, chloride, zinc
e.g. cl- is a cofactor for amylase
activate the enzyme when in appropriate place (precursor activation)
coenzymes
organic molecules derived from vitamins
some enzymes could cause damage if they are released in their active site form before they get to their target area
prosthetic groups
part of a protein that is needed for its function but is not made from amino acids -> tightly bound to the enzyme
e.g. zn2+ is part of carbonic anhydrase which is used in metabolism of co2