Enzymes Flashcards
why are enzymes relevant to medicine?
drug action (drugs can be enzyme inhibitors e.g. penicillin)
biochemical defects in enzymes cause disease (some genetically inherited e.g. sex-linked recessive haemophillia)
chemical diagnosis/prognosis (enzymes useful indicators of tissue/organ damage during injury)
how do enzymes work?
biological catalysts
specific action on substrate-specific active site
increase rate at which equilibrium is reached (dont change shift position of equilibrium as dont change concentrations of enzyme/substrate)
lower activation energy (reaction occurs at lower temp)
how do enzymes lower activation energy?
providing chemically competent groups (amino acids side chains) that help make transition from A–> B
align substrates so that orientation is optimised for reaction
stabilising transition states of substrates- prevent them from turning back to substrate
what is the active site of an enzyme?
region of enzyme which substrates binds and converted to product
3D structure made of crucial amino acid
binds via multiple weak interactions
complementary shape- gives specificity
what is an enzyme assay?
measuring enzyme activity
procedure for measuring biochemical activity in a sample
what is the Michealis-Menten model?
measure of enzyme affinity for its substrate
what is the Michealis constant (km)
ratio of forward and backward reaction rate constants
how does michealis constant (km) differ per enzyme?
fixed number dependent on individual enzyme
how does the value of michealis constant (km) differ with enzyme affinity?
smaller km = higher affinity
state the graphical/practical method of getting a value for km?
measure half Vmax
extrapolate down- gives km
missed out km values from page 1 of introduction to enzymes
go back to this during revision
which factors affect the rates of enzyme catalysed reactions?
substrate/enzyme concentration
temperature
pH- alteration in pH can ionise amino acid side chains which influence substrate binding, changing 3D structure of active site
inhibitors- natural/exogenous
what is irreversible enzyme inhibition?
covalent modification of amino acid side chains in active site
(e.g. modification of active site on serine by nerve agents)
what is reversible enzyme inhibition?
2 forms = competitive + non-competitive
what is competitive enzyme inhibition?
substrate and inhibitor have similar structures + compete for active site of enzyme