The rate of an enzyme-catalysed reaction is governed by a number of factors, including temperature, pH, enzyme concentration and
substrate concentration. Of these, substrate concentration is fundamental to enzyme kinetics because it determines how frequently
substrate molecules collide with — and bind to — an enzyme's active site. According to the Michaelis–Menten model, at low substrate
concentrations the initial reaction velocity rises steeply, as most active sites are vacant and the reaction is limited by substrate
availability; as substrate concentration increases, the velocity rises more slowly and approaches a maximum value (Vmax) once the
enzyme is saturated. This experiment investigates the effect of substrate concentration on the rate of starch hydrolysis by α-amylase, with
the extent of hydrolysis followed using the starch–iodine reaction. The objective is to determine whether the observed initial velocities
conform to the Michaelis–Menten equation and to estimate the apparent Michaelis constant (Km) of α-amylase under the conditions
tested. It is hypothesised that increasing starch concentration produces a hyperbolic relationship with initial reaction velocity, and that the
rate will eventually plateau as the enzyme becomes saturated.
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