The metabolism of carbohydrates, lipids, nucleic acids and proteins, but we have already underlined the fact that this division is rather arbitrary; it is justified mainly because it facilitates the presentation. In fact — as observed repeatedly — inter-relations between various types of compounds are numerous and the entire cellular metabolism must be regarded as a set of harmoniously integrated [...]
The replication of the DNA can be schematically divided in three steps: initiation, elongation and termination. Step # 1. The Initiation Step: As seen above, no DNA polymerase can perform any de novo synthesis (contrary to RNA polymerases which can initiate by placing a complementary ribonucleoside-5'-triphosphate opposite to the DNA to be transcribed). The primer 3'OH which will serve as [...]
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 [...]