Question

All monosaccharides containing five or six carbon atoms have:
A. open chain structures
B. pyranose structure
C. furanose structure
D. may have pyranose or furanose structures

Answer 1

Hint: Monosaccharides having five and six carbon are glucose and ribose and they can form both cyclic as well open chain structure. Furanose structure is shown by ribose ring like structure and glucose can show both pyranose (six membered ring) as well as furanose (five membered ring)structure.

Complete step by step solution:
Monosaccharides are the simplest form of carbohydrates and they don't have the ability to divide or hydrolyze further. Monosaccharides are divided into groups on the basis of carbon number and their nutritional importance. Pentose is a 5 carbon skeleton atom(ribose) and hexone contains six carbon in it (Glucose).
Monosaccharides show optical activity due to the presence of asymmetric carbon in monosaccharides attached with different functional groups.
Monosaccharides can form both cyclic as well as open chain structures and it shows stereoisomerism due to the formation of cyclic structures. Five membered rings (pentose) forms the furanose and the six membered ring (hexose) forms the pyranose as well as furanose.
Two stereoisomers of α and β configuration are produced during cyclization and at equilibrium monosaccharides solution forms in which mixture of cyclic as well as straight form is present.

Glucose is the most abundant and nutritionally most important monosaccharide, which is used as a cell fuel in the human body and found in body tissues and fluids.
Ribose is the RNA constituent and also acts as a metabolite in the pentose pathway.

Thus the correct option will be (A),(C) and (D).

Note: Monosaccharides are optically active and when passed through plane polarized light it will rotate to left (levorotatory or L form) or to the right (dextrorotatory of d-form). Most naturally occurring monosaccharides are d- stereoisomers and the digestive enzymes present in the body are specific for them so the monosaccharide of d-form is nutritionally very important.