The Synthetic Activities of the Cell^*

Abstract

UNLIKE the chemist, the animal cell has a very limited choice of raw materials from which synthesis must start. These are the components of the common foodstuffs. When they have undergone the preliminary processes of digestion they provide in all about thirty substances which may be regarded as available for the building up of new compounds by the cell. Given these raw materials, can we in every instance indicate which is the likely starting-point for the synthesis of substances the constitution of which is known or partly known? This question must still be answered in the negative for such well-known products as cholesterol and the unconjugated acids of bile.