Enzyme Mechanisms Flashcards
enzyme
biological catalyst that speed up rates of reaction that would otherwise be too slow to support life
catalyst
a chemical agent that changes the rate of reaction without being consumed by the reaction
substrate
reactant that enzyme acts on
active site
a pocket where the substrate binds - catalytic center where substrate is converted to product
where do enzymes act on substrates?
at their active site
what are enzymes composed of?
proteins (except 1) - ribozyme
how many reactions can an enzyme catalyze?
JUST ONE they are reaction specific
metabollic enzymes work in which direction?
most work both BOTH - forward and reverse
what does it mean to be substrate specific?
an enzyme can recognize one specific set of substrates related to the reaction it catalyzes
An enzyme can only act on one substrate but substrates can have multiple enzymes that react on it
what are the main types of enzymes?
simple, complex
what are the states of complex enzymes?
apoenzyme, holoenzyme
simple enzyme
composed only of protein component
complex enzyme
an enzyme that requires a cofactor to function in addition to its protein component
apoenzyme
inactive form of the enzyme because it is missing the cofactor
holoenzyme
active form of the enzyme with the cofactor
types of cofactors
inorganic, organic
examples of inorganic cofactors
metal ions, zinc, iron, copper
examples of organic cofactors
usually from vitamins of their derivatives
prosthetic group organic cofactor
covalently/permanently bonded to an apoenzyme
coenzyme organic cofactor
non-covenlently/reversibly bound to an apoenzyme
function of oxidereductase
shuffling electrons
function of transferase
moving chemical groups
function of hydrolase
breaking molecules with water
functions of lyase
breaking molecules without water
function of isomerase
changine molecular shapre (keeps the same atoms)
function of ligase
forming bonds between molecules
enzyme name ending
ase
what is the induced fit model?
as the substrate binds, the enzyme changes shape leading to a tighter fit bringing chemical groups in position to catalyze the reaction
binding of a substrate induces a favourable change in the shape o the active site
exergonic reaction
exothermic - a reaction that releases energy
activation energy
amount of energy needed to push the reactants over an energy barrier
how do enzymes speed up a reaction?
lower the activation energy
what are the mechanisms for lowering activation energy?
- proximity
- bond strain
- microenvironment
- covalent catalysis
proximity & orientation description
active site brings reactants closer together and in the correct orientation
bond strain description
active site bends bonds in substrate making it easier to break
microenvironment description
creates a favourable environment for the reaction
covalent catalysis description
enzymes may bind covalently to substrates in an intermediate step before returning to normal
how does covalent catalysis increase reactionr rate
properly orienting the susbtrate, changing the chemistry at the active site
limitations to enzyme activity
substrate concentration
temperature
pH
availability of cofactors
what is the correlation between substrate concentration and rate
direct, increase in concentration, increase speed of binding to active sites, increased reaction rate
what happens with enzyme saturation
active sites on all enzymes are engaged only way to increase productivity is to increase number of enzymes
increased temperature effects on enzyme activity
increased temp, increases speef of molecules, incrases collisions between substrate and active site
