Answer:
The correct answer is 3200000.
Explanation:
If there is only one amino acid in the peptide, the probable number of combinations would be 20. If there is only two amino acid in the peptide, the probable number of combinations will be 20^2. Similarly, for three amino acids in the peptide it would be 20^3 and for four it would be 20^4.
Thus, in the case of pentapeptide, that is, five amino acids in a peptide, the probable number of combinations will be 20^5, which comes out to be 3200000. Thus, the total number of different pentapeptides will be 3200000 that needs to be tested for receptor binding.