Adenine was first discovered in 1885 by the German physiologist Albrecht Kossel. He isolated adenine from the pancreas of oxen and named it "adenine" derived from the Greek word "aden," meaning gland.

The chemical structure of uracil, showing its single-ring pyrimidine structure. Uracil forms hydrogen bonds with adenine in RNA, contributing to the molecule's structure and function. (Image: Public ...

The reoxidation of reducing equivalents, NADH (reduced nicotinamide adenine dinucleotide) and FADH 2 (reduced flavin adenine dinucleotide), that are produced by the oxidation of carbohydrates (the ...