enzymes Flashcards
what do enzymes do
catalyse metabolic pathways
deficiency in function - leads to genetic disorder, accumulation of metabolites
what are conjugated enzymes
enzymes with something else attached
cofacters - non protein component added eg ions, vitamins
most vitamins act as coenzymes
describe oxidoreductases
adds or removes hydrogen ions in oxidation/reduction. can be used to detoxify alcohol from body
describe transferase
transfers functional groups between donors and acceptors
describe hydrolases
hydrolysis of substrates
described lyases
add something (water, ammonia, co2) across a double bond, or remove presence to create double bond
describe isomerases
isomerisation reactions
describe ligases
catalyse reactions where 2 groups are joined using atp
how does ph affect enzymes
affects r group charge, shape of active site, charge of substrate
what is vmax
vmax is max speed of the reaction, active sites are saturated. vmax is never reached - asymptote
what is Km
Km is the substrate concentration at half of vmax
a high Km - low affinity of enzyme to substrate
a low Km - high affinity of enzyme to substrate
examples of function deficiency
lactose intolerance - lack of lactase, most have it, symptoms later. treated with tablets or avoiding milk
albinism - lack of tyrosinase leads to no melanin. little pigment in skin, hair, eyes
describe reversible inhibition
competitive - inhibitor binds to active site - competes with substrate temporary more substrate, less inhibition increases Km, vmax same
non competitive -
inhibitor binds to other site
changes secondary and tertiary structure so substrate cant bind
Km same, vmax decreased
uncompetitive -
binds to the es complex, slow catalysis
Km decreased, vmax decreased
describe irreversible inhibition
permanently deactivate enzyme
do not need to be similar shape to substrate
what ways can enzyme activity be controlled
compartmentalisation
regulation by cell components
zymogens
covalent modification
describe compartmentalisation
organelles have optimum conditions, protects against lytic (chopping) enzymes
describe regulation by cell components
allosteric control - enzyme inhibited or promoted by small molecule
a positive effector increases activity, negative effector decreases
binding is cooperative - makes sigmoid graph
feedback control - regulation of allosteric enzyme. product in pathway activates or inhibits. ensures flux in pathways and creates sigmoid graph.
describe zymogens
destroy tissue that produces them, so an inactive form is generated which can be activated when needed eg digestive enzymes or trysinogen
activation occurs through addition or removal to the molecule
describe covalent modification
make or break covalent bonds between protein group and enzyme eg phosphate
this changes characteristics and conformation. if one form is active and the other is not - molecular switch ,reversible
