Total number of tripeptides possible by mixing of valine and prol… — Solution | JEE Chemistry

NVAEasyJEE 2023Proteins (Amino Acids, Structure, Denaturation)

Total number of tripeptides possible by mixing of valine and proline is:

Answer

Correct answer:8

Standard Method

Given: A tripeptide is formed from three positions using two amino acids: valine and proline.

Find: The total number of possible tripeptides.

Each position in the tripeptide can be occupied by either valine or proline. Since the sequence matters, the total number of distinct tripeptides is:

2^3 = 8

The possible tripeptides are Val-Val-Val, Val-Val-Pro, Val-Pro-Val, Val-Pro-Pro, Pro-Val-Val, Pro-Val-Pro, Pro-Pro-Val, and Pro-Pro-Pro.

Therefore, the total number of tripeptides is $8$ .

Assuming that order does not matter. That is wrong because Val-Val-Pro and Pro-Val-Val are different tripeptides. Count distinct sequences, not just compositions.
Using $2+3$ or $2\times 3$ instead of exponentiation. There are two choices for each of three positions, so the correct count is $2^3$ .

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