Explain the meaning of the designations \(D\) and 1 . as used to specify the configuration of monosaccharides.

Answer: The D and L designations indicate the configuration of a monosaccharide around the chiral center (asymmetric carbon) furthest away from the aldehyde or ketone group, specifically, the penultimate carbon atom. The D-configuration has the hydroxyl (OH) group on the right side, and the L-configuration has it on the left side in the Haworth projection. These designations are important because they affect the biological properties and functions of monosaccharides. Different organisms use different forms of sugars, and the majority of naturally occurring monosaccharides are in the D configuration. For example, D-glucose is the primary source of energy for our cells, while L-glucose cannot be metabolized by our body.