In previous work we suggested the hypothesis that the live cell is controlled by a molecular computer (m.c.) with a molecular memory and molecular address operators [1-3]. The presence in the cell of address RNAases and ligases predicted in this work has been demonstrated in [4, 5]. It was also shown that the m.c. of the neurones actually takes part in the work of the brain controlling the permeability of the membrane of the neurone from within [6-8]. The m.c. differs from the usual computer devices in that it has elements of extremely small size and uses for the search thermal motion.

The lower limit of the size of the computing elements of such devices is connected with the quantum properties of the substance - this is the physical limit of the miniaturisation of the elements of any computing device. However, the energetics of the molecular biochemical controlling systems of the cell as far from the physical limit. The physical value characterising the energetics of limiting computing devices is the "price of action" [9], the product of the energy expended on the computational operation and the duration of this operation [1,9]. This value is quantized and has a maximum quantum equal to the Planck constant h. As noted in [I, 3, 9] the price of action for a single operation on molecular words in the cell is above 10¹³h and for the fastest biochemical reactions in redox systems which might be used as arithmetical and logical elements not less than 1O¹⁰h [10-12].

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