Catalysts are species that accelerate chemical reactions without themselves being consumed in the process. The most efficient catalysts by far are the catalysts of biology, known as enzymes. The maintenance and creation of life in all its many and varied forms on Earth depends on the ability of enzymes to speed chemical Iransformations in biochemical systems. To this end, enzymes often display truly amazing vigour, specificity, and reliability. The fact that life itself depends on the action of enzymes testifies to their remarkable power.