take it up from the substances in the soil. They
incorporate it in their body substance. What makes phosphorus so
important that they cannot grow without it? The next insight was that
animals acquire it from their plant food. It is then found in bones, in
fat and nerve tissue, in all cells and particularly in the cell nuclei.
What are its functions there?

The answers to such questions were developed from the study of a
long-known process, the conversion of carbohydrates into carbon dioxide
and alcohol by yeast. It started with Eduard Buchner's discovery of
1890, that fermentation is produced by a preparation from yeast in which
all living cells have been removed. When yeast is dead-ground and
pressed out, the juice still has the ability to produce fermentation.

It is strange, but in many ways characteristic for the process of
science, that the "riddle" of phosphorus in life was solved by first
eliminating life. In such "lifeless" fermentations, Arthur Harden found
that the conversion of sugar begins with the formation of a hexose
phosphate (1904). The "ferment" of yeast, called zymase, proved to be a
composite of several enzymes. Hans von Euler-Chelpin isolated one part
of zymase, which remains active even after heating its solution to the
boiling point. From 1 kilogram of yeast, he obtained 20 milligrams of
this heat-stable enzyme, which he called cozymase and identified as a
nucleotide composed of a purine, a sugar, and phosphoric acid.[36] In
the years between the two World Wars, zymase was further resolved into
more enzymes, one of them the coenzyme I, which was shown to be ADP
connected with another molecule of ribose attached to the amide of
nicotinic acid, or diphosphopyridine nucleotide:

^ NH_{2}
/ \\ |
/ \\ N ^
|| |-CONH_{2} //\ / \\
|| | | || N
\ // | || |
N_{+} N--+ |
| | \//
| | N
H--C------+ H--C------+
| | | |
H--C--OH | H--C--OH |
| O | O
H--C--OH | H--C--OH |
| | | |
H--C------+ O O H--C------+
| || || |
CH_{2}--O--P--O--P--O--CH_{2}
| |