Answer the following seven questions a through g based upon

Answer the following seven questions (a through g) based upon a tripeptide sequence with the following amino adds (one-letter symbols are given): What are the full names of the amino acids? Spelling counts, but capitalization does not. For an acidic amino acid, assume it is ionized and use the - ate ending instead of - ic acid. What are the three-letter abbreviations for the amino acids? What is the overall charge of the most abundant tripeptide species at neutral pH (pH 7.0)? Enter your answer as a whole number. At physiological pH, what is the best description of the chemical properties of the side chain (R group What is the overall charge of the most abundant tripeptide species below pH 1.0? Enter your answer as a whole number. What is the overall charge of the most abundant tripeptide species at pH 11.5? Enter your answer as a whole number. What type of intermolecular force could the side chains form with water? (Note that these are interactions are with water, not with other amino acids.) hydrogen bonds ionic interactions hydrophobic interactions

Solution

Answers

a) Q: Glutamine I: Isoleucine K: Lysine

b) Q: gln I: Ile (ILE) K: Lys

c) +1 (i.e) one positive charge

Explanation: The overall charge at pH 7 is decided by the charge on the side chains of the aminoacids. The peptide doesn\'t add to the net charge as positive charge at the amino end gets balanced by one negative charge at the carboxy end. So in the tripeptide, Q I K, one addtional positive charge will be contributed by the additional amino group present in the side chain of K (Lysine)

d) Q: Uncharged, Polar ( if you can select only one select polar) I : Hydrophobic, uncharged ( if you can select only one select hydrophobic) K: positively charged

e) Answer: +2 (i.e 2 positive charge, as a whole number you can enter \'2\')

Explanation: At very low pH like 1.0 in this question, there is an abundance of H+ ions in solution so the -COOH groups do not dissociate to -COO- whereas the positive charge on -NH2 group remains intact. Since, tripeptide Q-I-K will have two -NH2 groups, it has a net positve charge (+2)

f) Answer: - 1 (i.e. 1 minus charge or minus 1)

Explanation : At very high pH like pH11.5 in this question, there are more -OH- ions in the solution and thus the COOH groups release the H+ ions and become negatively charged. The NH2 groups do not acquire H+ ions and thus say neutral. So in the tripeptide Q-I-K, there is net of one negative charge !

g) Answer : Hydrogen bonds