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Multiple Choice
The subunits (monomers) in cellulose are linked together by __________.
A
peptide bonds
B
phosphodiester bonds
C
β(1→4) glycosidic bonds
D
α(1→4) glycosidic bonds
Verified step by step guidance
1
Understand the structure of cellulose: Cellulose is a polysaccharide made up of glucose monomers. These glucose molecules are linked together in a specific way to form a long, unbranched chain.
Recall the type of bond that links monosaccharides in polysaccharides: Monosaccharides are connected by glycosidic bonds, which are covalent bonds formed during a dehydration reaction (removal of water).
Differentiate between α and β glycosidic bonds: In α-glycosidic bonds, the hydroxyl group (-OH) on the anomeric carbon of glucose is oriented downward, while in β-glycosidic bonds, it is oriented upward. This orientation determines the type of glycosidic bond formed.
Identify the specific glycosidic bond in cellulose: In cellulose, the glucose monomers are linked by β(1→4) glycosidic bonds. This means the bond forms between the β-configuration of the anomeric carbon (carbon 1) of one glucose molecule and the hydroxyl group on carbon 4 of the next glucose molecule.
Eliminate incorrect options: Peptide bonds link amino acids in proteins, and phosphodiester bonds link nucleotides in nucleic acids. α(1→4) glycosidic bonds are found in starch and glycogen, not cellulose. Therefore, the correct answer is β(1→4) glycosidic bonds.