<P> Monosaccharides in a closed - chain form can form glycosidic bonds with other monosaccharides , creating disaccharides ( such as sucrose ) and polysaccharides ( such as starch ) . Enzymes must hydrolyze or otherwise break these glycosidic bonds before such compounds become metabolized . After digestion and absorption the principal monosaccharides present in the blood and internal tissues include glucose , fructose , and galactose . Many pentoses and hexoses can form ring structures . In these closed - chain forms , the aldehyde or ketone group remains non-free , so many of the reactions typical of these groups can not occur . Glucose in solution exists mostly in the ring form at equilibrium , with less than 0.1 % of the molecules in the open - chain form . </P>
<P> Monosaccharides in a closed - chain form can form glycosidic bonds with other monosaccharides , creating disaccharides ( such as sucrose ) and polysaccharides ( such as starch ) . Enzymes must hydrolyze or otherwise break these glycosidic bonds before such compounds become metabolized . After digestion and absorption the principal monosaccharides present in the blood and internal tissues include glucose , fructose , and galactose . Many pentoses and hexoses can form ring structures . In these closed - chain forms , the aldehyde or ketone group remains non-free , so many of the reactions typical of these groups can not occur . Glucose in solution exists mostly in the ring form at equilibrium , with less than 0.1 % of the molecules in the open - chain form . </P>
the most common structure of sugars in solution is
the most common structure of sugars in solution is
ring form
ring form