We have recently presented a series of papers [A. Kummer, R. Ocone, Physica A 321 (2003) 587; A. Kummer, R. Ocone, Chem. Phys. Lett. 377 (2003) 627; A. Kummer, R. Ocone, Chem. Phys. Lett. 388 (2004) 322] where a thermodynamic theory of the cell cycle has been introduced and the analogy with the kinetic theory has been discussed. Based on such conceptual framework, here we clarify the concept of metabolic temperature [A. Kummer, R. Ocone, Physica A 321 (2003) 587], we show how the latter is extended from a single cell to a collection of cells and we discuss the significance of thermodynamic-like variables such as pressure. In deriving the explicit form (the constitutive relation) for the metabolic pressure, we conclude that any other state variable for the cellular 'ensemble' can be derived from the theory. (C) 2004 Elsevier B.V. All rights reserved.