Question

What are the key differences between the Michaelis-Menten model that describes enzyme kinetics and the Monod model that describes whole-cell or community kinetics?

Answer 1

Michaelis Menten model best explains the enzyme kinetics. It actually represented as an equation. It gives the relation between velocity(V max) and substrate concentration in an enzyme reaction. There is a constant in the equation (Km) called Michaelis constant.The enzyme (E) upon reaction with the substrate molecule (S) forms an intermediate enzyme substrate complex ( ES). This step is reversible one. The ES complex is then converted into product (P) and Enzyme, through an irreversible step.

The michaelis Menten equation is given as

Vmax is the maximum velocity ans S is the substrate concentration. It is represented as a graph.

The monod model ia actually the growth equation describing microbial growth kinetics. The growth rate of the microbial community is plotted as substrate concentration on the X axis, and specific growth rate on Y axis. The growth rate as a function of substrate concentration is expressesd in Monod equation as,

Both equations have the common form. But the key difference is that, Michaelis equation is based on theoritical values. But the Monod model is based on experiments and observations. That is the Monod model is not based on theories. The Michelis model is for the enzyme reactions, but Monod model is for the growth rate of micro-organisms.