Which of the following statements best describes glucose?
|A||It is a ketose and usually exists as a furanose ring in solution.|
|B||It is a C-4 epimer of galactose.|
|C||It is utilized in biological systems only in the L-isomeric form.|
|D||It is produced from dietary starch by the action of β-amylase.|
a. Glucose and galactose differ only in configuration around carbon 4, and so are C-4 epimers that are interconvertible by the action of an epimerase.
b. Glucose is an aldose sugar that typically exists as a pyranose ring in solution; fructose, however, is a ketose with a furanose ring.
c. The D-isomeric form of carbohydrates is most typically the form found in biologic systems, in contrast to amino acids.
d. Salivary amylase does not produce monosaccharides. Homopolysaccharides of glucose include branched glycogen in which the glycosidic linkages are the β form, as well as unbranched cellulose that has β linkages.