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Bioinorganic Chemistry: A Short Course, Second Edition, by Rosette M. Roat-Malone

Copyright © 2007 John Wiley & Sons, Inc.

GROUP I AND II METALS IN

BIOLOGICAL SYSTEMS:

HOMEOSTASIS AND GROUP

I BIOMOLECULES

5.1 Introduction,

Several group I and II metal ions belong to the essential chemical elements

“ macrominerals and ions category ” (Na + , K + , Mg 2+ , Ca 2+ , Cl − , PO 43 −, SO 42 −)

defi ned in Section 1.2. Group I and II metal ions have roles in maintaining

osmotic and electrolytic control in biological species. They are involved in

physiological signaling and triggering as well as photosynthetic events. As with

all chemical elements and ions, they must be made available when and where

they are needed — homeostatic control. The cations passively diffuse and are

actively pumped across cell membranes, many times against concentration

gradients. Table 5.1 summarizes the characteristics of Group I and II ions, lists

some biological molecules that feature them, and indicates the toxicities that

arise in nonbiological members of the groups. Reference 1 contains more

information on the transport and storage of metal ions in its Chapter 3 ; also

see Chapters 6 and 7 of reference 1 for more information on Groups I and II

metals in biological systems. Reference 2 comprehensively reviews the biologi-

cal chemistry of Groups I and II metals in its Chapters 8, 9, and 10.

In this chapter, homeostasis of Groups I and II metals will be described,

and several systems involving the Group I metal ions sodium and potassium

will be discussed in detail. In Chapter 6 , several topics involving Group II

metal ions will be presented.