Question 1091943
.
An octapeptide is known to contain four of one amino acid, two of another and two of third. How many different amino acid sequence are possible?
~~~~~~~~~~~~~~~~


To correctly answer this question, we need to know what sequences (what connections and interconnections) are allowed.


If ALL sequences and connections are allowed in one-line-arrangement, then the following logic works:


<pre>
    In total, there are 4 + 2 + 2 = 8 amino acid (acids ?).

    Anyone of 8 acids           can be placed in the 1-st position.
    Anyone of remained 7 acids can be placed in the 2-nd position.
    Anyone of remained 6 acids can be placed in the 3-rd position.
    Anyone of remained 5 acids can be placed in the 4-th position.

    . . . .   and so on  . . . . 

    Anyone of remaining 2 acids can be placed in the 7-th position.   
    And    there is no choice (except the remained 1 last acid) in the 8-th position.

    If this logic is correct from the Chemistry/Biochemistry point of view,
    then the answer is  8*7*6*5*4*3*2*1 = 40320 different amino acid sequences are possible.
</pre>

I am not a Chemist in my education, so my logic easily can be wrong.


It is your responsibility to evaluate if it is True or False.


If it not difficult to you, I would appreciate your feedback, which you can send me through the "Thank you" note.


In this case, please refer to the Problem ID number, which is 1091943.


Thank you and good luck !!



-----------------
From Wikipedia,  https://en.wikipedia.org/wiki/Peptide

<pre>
    An octapeptide has eight amino acids (e.g., angiotensin II).
</pre>

From Wikipedia,  https://en.wikipedia.org/wiki/Angiotensin#Angiotensin_II

<pre>
    Angiotensin II
    Asp-Arg-Val-Tyr-Ile-His-Pro-Phe | His-Leu
</pre>