Pluricellular organisms are characterized by the existence of tissues, i.e. sets of cells which have acquired specialized functions. This specialization is advantageous in the sense that it permits a distribution of work but it necessitates means of controlling and integrating the activities of various tissues. Hormones constitute precisely a means of communication between territories distant from one another. It was [...]
The determination of the base sequence of a nucleic acid is much more difficult than the determination of the sequence of amino acids of a protein, because there are only 4 types of monomers instead of 20. This explains why one began with the determination of the sequences of transfer ribonucleic acids (more than 200 sequences are known); these do [...]
The effects of variations of substrate concentration on the velocity of an enzymatic reaction. We may only add that in some cases, variations of substrate or co-substrate concentration [S] can exert important effects on the metabolism by permitting either the synthesis, or on the contrary the degradation of a substance X, or by determining the metabolic pathway in which a [...]