NUTRITION 
359 
complexity of even the simplest carbohydrates, nor of the fact that a mere difference 
in the position of certain atoms or groups of atoms, which does not affect the per- 
centage composition at all, gives wholly different chemical and physical characters 
to the substance. 
Thus, grape sugar (glucose) exists in two forms, one of which rotates a beam of 
polarized light to the right and the other to the left; the one, ^-glucose, is abundant 
in plants; the other, /-glucose, does not occur in nature but has been made arti- 
ficially. The difference is shown partly in the three following structural formulas, 
which all sum 
OH H OH OH 
COH C C C C CH 2 OH =<f-glucose 
H OH H H 
H OH H H 
I ! I I 
COH C C C C CH 2 OH =/-glucose 
OH H OH OH 
Further, fruit sugar (^/-fructose) is abundant in plants, and its structure is quite 
different from glucose : 
H OH OH 
CH 2 OH CO C -C C CH 2 OH =d-fructose 
I I I 
OH H H 
Another sugar especially abundant in plants, cane sugar, Ci 2 H 22 On, probably has 
this formula: 
/CH^_ CH 2 OH 
/ CHOH ^ 
O C 
5 1 
\ CHOH 
/CHOH 
o I 
\ CHOH 
1 
\l 
CHOH 
1 
\CH 
CH 2 OH 
CH 2 OH 
the modified 
the modified 
glucose unit 
fructose unit 
saccharose 
and when it breaks at the O bond, it takes up H -OH and resolves itself into a 
molecule of glucose and a molecule of fructose. These two hexose sugars, glucose 
and fructose, and the disaccharide, cane sugar, are the only sugars which occur in 
abundance in plants; though mannose, galactose, and maltose are formed in the 
course of digestion. 
