ll animal nucleic acids are identical and all plant nucleic acids
are identical; but those of plant origin differ from those found in animal
cells in the character of the carbohydrate and that of one of the
pyrimidine bases which are present in the molecule, as shown in the
following tabulation of their composition:

Animal nucleic acid Plant nucleic acid
Phosphoric acid Phosphoric acid
Hexose (levulose) Pentose (_d_-ribose)
Guanine Guanine
Adenine Adenine
Cytosine Cytosine
Thymine Uracil

The structure of the plant nucleic acid may be represented by the following
formula:

OH
|
O=P--O--carbohydrate-guanine group
|
O
|
O=P--O--carbohydrate-adenine group
|
O
|
O=P--O--carbohydrate-uracil group
|
O
|
O=P--O--carbohydrate-cytosine group
|
OH

That this is probably a correct representation of the general arrangement
in this compound, is indicated by the fact that by different methods of
hydrolysis it is possible to split off either the purine and pyrimidine
bases, leaving a carbohydrate ester of phosphoric acid; or the phosphoric
acid, leaving carbohydrate combinations with the nitrogenous bases.

Nucleic acid, prepared from animal glands which contain large proportions
of it, is a white powder, which is insoluble in water, but when moistened
forms a slimy mass. It is almost insoluble in alcohol, but dissolves
readily in alkaline solutions, forming a colloidal solution which readily
gelatinizes (see chapter on Colloids). Solutions of nucleic acids are
optically active, probably because of the carbohydrate constituents.

From their structure and properties, it is apparent that nucleic acids are
on the border line between carbohydrates, plant amines, and proteins. They
undoubtedly play an important part, both in cell-growth and in the
synthesis of proteins from carbohydrates and ammonium compounds.

References

BARGER,