A tentative description of the mechanism of an enzymic reaction is given, making use of simple concepts of elementary quantum mechanics. The model is developed for the particular case in which the reaction consists of the transfer of a group from one molecule to another. The basic idea is that the binding energy of the group to the complex, which is composed of the enzyme and the first substrate, must be equal to the binding energy of the same group to the second substrate. Thus, the system is in a degenerate stationary state when no interaction occurs. In a collision, the two parts of the system interact and the degenerate state splits into two stationary states of somewhat different energies, which are the symmetrical and the antisymmetrical linear combinations of the unperturbed wave functions. If the group is initially bound to the first substrate, the state of the system is not a stationary one, so that the probability of binding to each substrate varies with time. When the group has passed to the second substrate, the enzyme-first substrate complex dissociates and the reaction is over. The model can be easily applied to any other type of enzymic reaction. The importance of such a resonance transfer mechanism in cell biology is stressed and two examples are given of well-known cellular phenomena which can be easily explained on these grounds.