Question

Suppose you mix leucine, tyrosine, histidine and cysteine together and allow them to form tripeptides. Which of the following will form?

A) Tyr-His-Cys

B) His-Tyr-Cys

C) Cys-Cys-Tyr

D) Leu-Tyr-His

E) None of the Above

Answer 1

Among the given acids which has lower pKa is starting amino acid

because , a CO-NH (peptide) bond is formed between the amino acids when they are allowed to join

Here His has lower pKa for COOH among all amino acids ,

So His is the starting amino acid

Answer is B ( if its single option )

But actually is should be a more than one answer question

Because all A,B,C,D can form (if more than one molecule of Cys is used )

A,B,C forms ( of only single molecules are used)

So choose from the conditions