Quantitative aspects of comparative biochemistry

These quantitative differences do not always tell in favour of the larger creature. Man, for example, is 15 times more sensitive to atropine than the rabbit. However, he can safely take a dose of strychnine which would kill more than his own weight of rabbits, and he is unaffected by a concentration of hydrocyanic acid that is instantly fatal to dogs. 

Remarkable differences can also be found within a single species. For example, the glutamine synthetase from rat kidney acts on its substrate ten times faster than does the analogous enzyme from rat muscle (Iqbal and Ottaway, 1970). Again, cancer cells maintain a more rapid cell cycle than normal cells hence they are more sensitive to drugs which interfere with the synthesis of nucleotides. 

For further reading on the selective metabolism of foreign substances, see Lehninger (1982) and Stryer (1981) and for plant biochemistry, see Bonner and Varner (1976). A simple account, for revising the basic facts, can be found in Campbell and Kilby (1975), and a related work in pictorial form, suitable for projection in Campbell and Smith (1982). 

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