Question

Name the type of covalent bond(s) joining monomers in these biopolymers. (a) Polysaccharides (b) Polypeptides (c) Nucleic acids

Short answer

Answer: (a) In polysaccharides, glycosidic bonds join the monomers. (b) In polypeptides, peptide bonds join the monomers. (c) In nucleic acids, phosphodiester bonds join the monomers.

Step-by-step solution

(a) Polysaccharides

Polysaccharides are formed by joining monosaccharides (simple sugars) through covalent bonds called glycosidic bonds. The glycosidic bond forms between the hydroxyl groups of two monosaccharides, in which a water molecule is released during the process of dehydration synthesis or condensation. Therefore, the type of covalent bond joining monomers in polysaccharides is glycosidic bond.

(b) Polypeptides

Polypeptides are formed by the polymerization of amino acids. The covalent bond that joins amino acids together is called a peptide bond. A peptide bond is formed between the carboxyl group of one amino acid and the amino group of another amino acid, releasing a water molecule in the process. Thus, the type of covalent bond joining monomers in polypeptides is a peptide bond.

(c) Nucleic acids

Nucleic acids, such as DNA and RNA, are polymers comprised of nucleotide monomers. The covalent bond that joins these nucleotides together is called a phosphodiester bond. A phosphodiester bond is formed between the 5' phosphate group of one nucleotide and the 3' hydroxyl group of another nucleotide. This bond creates the backbone of the nucleic acid and links the sugar and phosphate groups of adjacent nucleotides. Therefore, the type of covalent bond joining monomers in nucleic acids is a phosphodiester bond.