enzymes Flashcards
what are enzymes?
catalysts in living cells
descrtibe induced fit
active site and substrate dont fit exactly, the enzyme changes shape when the substarte binds
which enzymes are not proteins?
ribozymes and catalytic RNA
what is Ea?
energy required to initiate reaction
which factors may affect the rate of an enzyme reaction?
temp, pH, enzyme concentration, substarte concentration, inhibitors & activators, covalent modification
what is Vmax?
maximum rate of reaction (enzyme saturated with substrate
what is Km?
conc of substrate when rate is 1/2 max value
what is occuring when Km value is low?
enzyme saturated with substrate, act at fairly constant rate regardless of variations in substrate concentration, high affinity
what is occuring at high Km values?
enzyme not saturated with substrate, activity will vary as substrate concentration varies, low affinity
what is lineweaver-burk plot?
more accurate estimate of Vmax and Km, obtained by plotting 1/V against 1/S and reading of two intercepts
in a linewweaver-burk plot what is the the gradient and the y and x axes equal to?
gradient = Km/Vmax
y intercept = 1/Vmax
x intercept = -1/Km
most natural enzyme inhibitors are what:
irreversible inhibitors or reversible inhibitors?
reversible
describe feedback inhibition
product of metabolic pathway builds up in cell, product acts as inhibitor of earlier step in the pathway
how can competitive inhibition be overcome?
increase substrate concentration
Are Vmax and Km altered by the presence of a competitve inhibitor?
Vmax - unaltered as large substrate quantity can outcompete
Km - inhibitor competes for active site decreasing affinity
