more enzymes Flashcards
enzymes are..
macro molecules whose function is to increase the rate of reaction–> generally do this by reducing transition state energy for a reaction
general properties of enzymes
catalyst - enzymes end in the state they started -specific -protein itself is not changed in reaction -fast
catalysed reactions vs normal reactions
no enzyme: s–> p enzyme: E+s –> ES–> EP–> E+ P many more intermediate reactions
catalysed reactions assume that
-release of product is very fast, compared to the reaction itself -reverse reaction is sufficiently slow
how is the transition state barrier reduced? 2 ways
- stabilise the unfavourable intermediate
- make possible less favourable reactions
stabilise the unfavourable intermediate
- charge-charge interactions
- h bonding
- protecting hydrophobic groups
make possible less favourable reactions
- provide acid/base conditions
- allow oxidation.reduction
- provide a small vacuum
- provide attacking group
- provide a metal ion
Vmax=
maximal rate -reveals turn over number–> also called Kcat
Km
michaelmas constant -measure of catalytic efficiency
- the conc of substrate at which half the active sites are filled
- provides a measure of the substrate conc needed for significant catalysis to occur
Km values of enzymes range widely..
between 10^-1 and 10^-7
what does Km depend on..
the substrate and conditions such as pH
a high Km indicates
weak bonding
a low Km indicates
strong bonding
a low Km indicates
strong bonding
when entropy is large than Km..
the rate of catalysis (V) is equal to Vmax–> a function of Kcat
Kat take sinto cosndieration..
the rate of catalysis and strength of the ES interaction
M-M proves that
when the conc of substrate drops so does the rate
two types of graphs which use M-M kinetics
Hanes woolf Line-weaver
two types of graphs which use M-M kinetics
Hanes woolf Line-weaver
important enzyme characteristics..
Km and Vmax
working out the constants for a give enzyme requires..
several experiments
what must the experiments provide
-provide the value for Vo (velocity) for a least 5 (8-10 preferable) values -these values of [s] must be both sides of Km for a good result constants of enzymes can now be calculated
lineweaver plot
hanes-woolf
arrhenius equation
Michaelis-Menten equation
M-M graph
arrhenius equation gives the relationship between
activation energy and the reaction rate constant
