Final answer:
The number of different amino acid sequences for a polypeptide chain 10 amino acids long is 20^10, which gives us 10,240,000,000 possible sequences.
Step-by-step explanation:
To calculate the number of different amino acid sequences for a polypeptide chain that is 10 amino acids long, one must consider that there are 20 common amino acids that can be used at each position. Since each position in the polypeptide chain can be occupied by any of the 20 amino acids, the total number of different sequences can be calculated using the formula for permutations with repetition, which is 20^n, where 'n' is the number of positions in the chain.
In this case, with n = 10, the formula becomes 20^10. Therefore, the number of different amino acid sequences for a polypeptide chain 10 amino acids long is 20^10, which equals 10,240,000,000 possible sequences.