BCEM 393 Lecture Notes - Lecture 8: Turnover Number, Enzyme Kinetics, Ionic Strength
Enzymes — Part 2
KINETICS — RATES OF REACTION
- Kinetics = Study of the rates of chemical reactions
- V = d[P]/dt = - d[A]/dt
- For a First Order Reaction: V = k[A]
- Units for first-order rate constant, k is s-1 or min-1
- Many important biochemical reactions are bi-molecular, which makes them second-order
reactions
- For 2nd order reactions,
the rate constant has
the units of M-1 s-1
- When measuring the
rates of enzyme
catalyzed bimolecular
reactions, we often use a high fixed concentration of either A or B so that the reaction
becomes pseudo-first-order
ENZYME CATALYZED RATES
- With an enzyme, the rate depends on the concentration of
the substrate, but does not vary as one might expect
- Experiment:
- Step 1: Using a particular initial concentration of
substrate, measure the concentration of product over time
- Step 2: Repeat, using different initial concentrations of
substrate
- Step 3: Decrease the initial rate, Vo in each case
- Step 4: Plot the initial rate, Vo, for each
concentration of substrate versus [S]
- Maximum velocity, Vmax, is the limiting rate
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Document Summary
(cid:1688)kinetics(cid:1689) = study of the rates of chemical reactions. For a first order reaction: v = k[a] Units for first-order rate constant, k is s-1 or min-1. Many important biochemical reactions are bi-molecular, which makes them second-order reactions. For 2nd order reactions, the (cid:1688)rate constant(cid:1689) has the units of m-1 s-1. When measuring the rates of enzyme catalyzed bimolecular reactions, we often use a high fixed concentration of either a or b so that the reaction becomes (cid:1688)pseudo-first-order(cid:1689) With an enzyme, the rate depends on the concentration of the substrate, but does not vary as one might expect. Step 1: using a particular initial concentration of substrate, measure the concentration of product over time. Step 2: repeat, using different initial concentrations of substrate. Step 3: decrease the initial rate, vo in each case. Step 4: plot the initial rate, vo, for each concentration of substrate versus [s] Maximum velocity, vmax, is the limiting rate.