kinetics and units

• zero-order kinetics - reaction rate is determined by an enzyme concentration
• in zero-order kinetics, there is excess substrate, meaning the rate of reaction is determined by the amount of enzyme
• in first order kinetics, the reaction rate is determined by substrate concentration
• enzyme activity is measured using fixed time reaction or continuous monitoring (kinetic)
• for kinetic enzymes (most common enzyme assay) - mix enzyme and substrate, measure absorbance at intervals and incubate if needed
• international unit -  the amount of enzyme that will catalyze 1 micromol of substrate per minute under specified conditions of temperature, pH, substrate, and activators
• assays we use employ zero order kinetics, meaning we always add excess substrate; allows more time for reaction to be measured