Full resolution (JPEG) - On this page / på denna sida - III. The Carbohydrates - 1. Monosaccharides
<< 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.
204 THE CARBOHYDRATES.
the hexose group, and in fact all the hexoses do not ferment, and they
do not all ferment with the same readiness. d-Glucose and d-mannose
ferment readily, but d-galactose only with difficulty. The Worms of
the above-mentioned sugars do not ferment, and from the racemic forms
of these sugars the optical Z-antipode can be prepared by the fermenta-
tion of the d-sugar. Among the ketoses the d-fructose ferments while
the sorbose does not. Among the sugars containing nine atoms of car-
bon, the nonoses, the mannonose ferments while the glucononose does
not. In regard to the fermentability of the triose, dioxyacetone, see
page 205. The different behavior of the various sugars with yeast stands
in fixed relation to their configuration, and is not only of great importance
for the behavior of the sugar in lower organisms, but also for their behavior
in higher developed organisms. Thus the investigations of Neuberg
Wohlgemuth x
upon arabinose and of Neuberg and Mayer 2
on man-
noses have shown that in rabbits the Z-arabinose and the d-mannose are
much better utilized than d- and r-arabinose or I- and r-mannose. See
also pages 61-62.
In the alcoholic fermentation the sugar is decomposed according
to the general equation C6Hi206 = 2C2H60-f2C02. The exact process
is not clear, and seems to be rather complicated. On page 52 it has
been mentioned that for the action of the fermentation enzymes the
presence of a dialyzable substance present in the press-juice is neces-
sary (Harden and Young 3
). On the other hand the fermentation
power of the press-juice can also be considerably increased by the addi-
tion of secondary sodium phosphate. The phosphoric acid in the press-
juice after fermentation is only partly precipitable with magnesia mixture
(Harden and Young). The most favorable action of boiled press-
juice is inhibited by lipase (Buchner and Klatte). According to
Harden and Young we must consider the action of boiled press-juice
and of phosphate in that first a hexose-phosphoric acid ester is produced
with the simultaneous formation of carbon dioxide and alcohol, according
to the following formula:
2C6H1 2O6 +2R2HPO4 = 2CO2+2C2H6O+C6H1 0O4(PO4R2)2+2H2O.
The hexose phosphate can then be split into hexose and phosphate
by a special enzyme. The hexose phosphoric acid has been isolated
as a lead salt by Young. Glucose, fructose and mannose produce in
their fermentation the same hexose phosphoric acid. According to
1
Zeitschr. f. physiol. Chem., 35.
*1M&., 37.
3
Literature in Harden and Young, Bioch. Zeitschr., 32, 173 (1911) as well as
Buchner and Klatte, ibid., 8, 520 (1908).
<< prev. page << föreg. sida << >> nästa sida >> next page >>
