Chapter 1 Biochemistry and the Unity of Life 19 50 What would interactions betwe

Question

Chapter 1 Biochemistry and the Unity of Life 19 50 What would interactions between side chains of aspartate and arginine at neutral pH be? A) hydrophobic B) ionic C) hydrogen bonding D) steric E) covalent 51 Which amino acid has a side chain with a hydroxyl group? A) serine B) alanine C) tryptophan D) histidine E) glutamine 52 Which amino acid has a carboxyl group in its side chain? A) glutamine B) galanine C) cysteine D) glutamate E) None of the above. 53 What would the overall charge of a peptide of the following peptide sequence at pH 1 be (Asp- Gly-Arg-His)? A)-1 B) 0 C) 1 D) 2 E) 3 54 Which of the following amino acids would most likely be soluble in a nonpolar solvent such as benzene? A) valine B) histidine C) glutamine D) glycine E) All of the above.

Explanation / Answer

50) at pH 7, the side chain of aspartate is negatively charged and the side chain of arginine is positively charged.

Hence their interaction will be B. Ionic as one can readily donate an electron and the other can accept.

51) A. Serine. The side chain of Serine is CH2OH hence being the only amino acid among the given ones to have a hydroxyl group in the side chain.

52) D. Glutamate. The side chain of glutamate is CH2-CH2-COOH hence being the only amino acid among the given ones to have a carboxy group in the side chain.

53) E. 3 (based on the charge of individual amino acid at pH 1 which is determined by the pI of the amino acid and the number of ionisable groups.)

54) A. Valine. Valine is the most non polar amino acid amongst the given amino acids hence will have maximum solubility in non polar solvents like benzene.

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