Amino acids are bi-functional compounds, with a general formula NH2CH(R)CO2H. A tripeptide is formed between Alanine (ala), Glycine (gly), and lysine (lys). There is no repetition of amino acid in this tri-peptide; suggest how many tri-peptides are possible?
Correct answer: B. 6
- A. 9
- B. 6
- C. 3
- D. 12
Explanation
For such questions, try to make all possible combinations of amino acids. They include:ala-gly-lys gly-ala-lys lys-ala-glyala-lys-gly gly-lys-ala lys-gly-alaThus, there are six possible amino acids that can be formed without repetition. If repetition was allowed, then the answer would be 27 (3 x 3 x 3).NOTE: Tripeptides which can be written in reverse such as ala-lys-gly and gly-lys-ala are different and distinct from each other so do not eliminate such examples or count them as one instead of two, because in such tripeptides the C-terminal and N-terminals vary.
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Proteins are classified by shape, composition and structure, from primary amino acid sequence to secondary, tertiary and quaternary organisation, and their biological roles are linked to this structure. Enzymes are examined as protein biocatalysts, including active sites, substrate specificity, activation energy, cofactors and factors affecting activity.
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