What types of interactions can occur between the side chains of the following amino acids that would help maintain the tertiary structure of a protein? a. cysteine and cysteine b. glutamine and serine c. glutamic acid and lysine d. proline and leucine

First, we must identify the types of side chains present on the amino acids and understand which of these can interact with each other. a. Cysteine has a thiol group (-SH) on its side chain. b. Glutamine has an amide group (-CONH2) on its side chain, and serine has a hydroxyl group (-OH) on its side chain. c. Glutamic acid has a carboxyl group (-COOH) on its side chain, and lysine has an amine group (-NH2) on its side chain. d. Proline has a pyrrolidine ring, and leucine has an aliphatic hydrophobic side chain.

Now, let's analyze which interactions could occur between the side chains of each amino acid pair: a. Between cysteine and cysteine: - Disulfide bonds (a covalent bond between two sulfur atoms) can be formed between the thiol groups of two cysteine residues. b. Between glutamine and serine: - A hydrogen bonding interaction can occur between the amide group in glutamine and the hydroxyl group in serine. c. Between glutamic acid and lysine: - An ionic interaction (salt bridge) can form between the carboxyl group in glutamic acid and the amine group in lysine. d. Between proline and leucine: - Hydrophobic interactions can occur between the aliphatic part of the proline side chain and the hydrophobic side chain of leucine. In conclusion, the types of interactions that can occur between the side chains of the given amino acid pairs and help maintain the tertiary structure of a protein are: a. Disulfide bonds between cysteine and cysteine b. Hydrogen bonding between glutamine and serine c. Ionic interactions between glutamic acid and lysine d. Hydrophobic interactions between proline and leucine.