enzymes Flashcards
do enzymes raise or lower energy of activation
lower
function of isomerases
rearrange atoms
function of ligase
use of ATP to combine molecules
function of lyases
removal or add of atoms to or from double bond
what are apoenzymes and holoenzymes
apoenzyme = inactive enzyme i.e withoutnon protein cofactor
holoenzyme = enzyme with its nonprotein cofactor
give an example of cofactors
inorganic ions
what features of the active site allows for reactions to occur faster
the shape and chemical enviroment
how do enzymes bind to the substrate
via h bonds, salt bridges and hydrophobi interactions
what are the three types of enzyme specificity
absolute - catalyse one type of reaction for a single substrate
group - catalyse one type of reaction for simialr substrates
linkage -catalyse one type of reaction for a specific bond
what is the turnover number
number of molecules of substrate converted to product per enzyme molecule per second
how are enzymes arranged in the cell
segregated in specific organelles so enzyme reactions do not complete other reactions
what is an isoenzyme
different forms of enzymes that do the same reactions in different tissues
what is free energy of activation
the energy barrier separating reactant and product
what is the x and y intersecgt on the lineweaver-burk plot
y intersect = 1/Vmax
x intersect = -1/Km
what is micheals constant
Km
where Km is the substrate conc at which the reaction velocity = 1/2Vmax
what does a small Km or a Large Km mean
small = high substrate affinity
- low substrate needed to half saturate the enzyme to reach a velocity of 1/2Vmax
large = low substrate affinity
- high substrate level needed to half saturate the enzyme to reach a velocity of 1/2Vmax
what are the factors affecting enzymes
substrate conc, pH, temperature, inhibitors, activaors, modulators
what effect has pH on enzyme
denaturation, can affect the charges on the enzyme and substrate- influences binding
what effect has temp on enzymes
denature at high temps, enzumes have an optimum temp but are fully denatured at 70 degreec c
what are inhibitors
cause a loss of enzyme activity, three types:
- reversible
- irreversible
- allosteric
what are the types of reversivle inhibitors
competitive, noncompetitive, uncompetitive
what are the irreversible enzymes
active site directed or suicide inhibitor
what is a reverse inhibitor
binds to enzyme via non covalent bonds (weak). they go on and off allowing the enzyme to lose and gain ability. inhibition effect is reversed by substrate conc increase
what is an irreversible inhibitor
binds at or near the active site via covalent bonds. sometimes they can destroy a crucial functional group in the enzyme. enzyme activity is not regained by increasing S levels
