Full resolution (JPEG) - On this page / på denna sida - III. The Carbohydrates - 3. Colloid Polysaccharides - The Cellulose Group (C6H10O5)x
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
CELLULOSE. 231
The Cellulose Group (C6Hi O5)x.
Cellulose is that carbohydrate, or perhaps more correctly, mixture
of carbohydrates, which forms the chief constituent of the walls of the
plant-cells. This is true for at least the walls of the young cells, while
in the walls of the older cells the cellulose is extensively incrusted with a
substance called lignin, and with many other cellulose derivatives and
compounds.
The true celluloses are characterized by their great insolubility. They
are insoluble in cold or hot water, alcohol, ether, dilute acids, and alkalies.
We have only one specific solvent for cellulose, and that is, an ammo-
niacal solution of copper oxide called Schweitzer’s reagent. The
cellulose may be precipitated from this solvent by the addition of acids,
and obtained as an amorphous powder after washing with water.
Cellulose is converted into a substance, so-called amyloid, which
gives a blue coloration with iodine, by the action of concentrated sul-
phuric acid. With oxidizing agents (nitric acid, etc.) oxycelluloses are
produced. By the action of strong nitric acid or a mixture of nitric
acid and concentrated sulphuric acid, celluloses are converted into nitric-
acid esters or nitrocelluloses, which are highly explosive and have found
great practical use.
The ordinary celluloses when treated at the ordinary temperature
with strong sulphuric acid and then boiled for some time after diluting
with water are coverted into glucose. In this case it must be observed,
according to Maqtjenne, that it is not maltose that is produced as an
intermediate step, but another disaccharide, called cellose or cellobiose.
The cellulose, at least in part, undergoes decomposition in the intestinal
tract of man and animals. A closer discussion of the nutritive value
of cellulose will be given in a future chapter (on digestion). The great
importance of the carbohydrates in the animal economy and to animal
metabolism will also be given in the following chapters.
Hemicelluloses are, according to E. Schulze, 1
thoseconstituents of the cell-
wall related to cellulose which differ from the ordinary cellulose by dissolving
on heating with strongly diluted mineral acids, such as 1.25 per cent sulphuric
acid, and of yielding arabinose, xylose, galactose, and mannose instead of glucose.
Those hemicelluloses which serve partly as reserve food and partly as support-
substance, are very widely distributed in the plant kingdom. It must be recalled
that according to Bierry and Giaja 2
the digestive organs of different inverte-
brates (Helix, Astacus, Maja. Hommarus) contain enzymes which have an
energetic splitting action upon such polysaccharides as well as on the natural
celluloses.
1
E. Schulze, Zeitschr. f. physiol. Chem., 16 and 19, with Castro, ibid., 36.
2
Bioch. Zeitschr., 40, 370 (1912).
<< prev. page << föreg. sida << >> nästa sida >> next page >>
