| | | |
|| || CH O=C C--H O=C CH
|| || // | || | ||
N--C--N H--N--CH HN--CH

Guanine Cytosine Uracil

The carbohydrate is ribose or deoxyribose.

CHO CHO
| |
H--C--OH HO--C--H
| |
HO--C--H HO--C--H
| |
HO--C--H HO--C--H
| |
CH_{2}OH CH_{2}OH

Arabinose L-Ribose

Fischer and Piloty, 1891

H
\(1)/-----O-----\(4) (5)
C CH--CH_{2}OH
/ \(2) (3)/
HO CH_{2}--HC(OH)

Deoxyribose

The exact position of phosphoric acid was established after long work
and verified by synthesis.[33]

A compound of adenine, ribose, and phosphoric acid was found in yeast,
blood, and in skeletal muscle of mammals. From 100 grams of such muscle,
0.35-0.40 grams of this compound were isolated. If the muscle is at
rest, the compound contains three molecules of phosphoric acid, linked
through oxygen atoms. It was named adenosine triphosphate or
adenyltriphosphoric acid,[34] usually abbreviated by the symbol ATP. It
releases one phosphoric acid group very easily and goes over in the
diphosphate, ADP, but it can also lose 2 P-groups as pyrophosphoric acid
and leave the monophosphate, AMP.

N==C--NH_{2}
| |
HC C--N +----O----+
|| || \\ | |
|| || CH | OH OH | H OH
|| || / | | | | | /
N--C--N-----C--C---C--C--C--O--P=O
| | | | | \
H H H H H OH
\---------/\---------------/\--------/
Adenine D-Ribose Phosphoric
acid

This change of ATP was considered to be the main source of energy in
muscle contraction by Otto Meyerhof.[35] The corresponding derivatives
of guanine, cytosine, and uracil were also found, and they are active in
the temporary transfer of phosphoric acid groups in biological
processes.

Thus, the study of organic phosphates progressed from the comparatively
simple esters connected with fatty substances of organisms to the
proteins and the nuclear substances of the cell. The proportional amount
of phosphorus in the former was larger than in the latter; the actual
importance and function in