Where are long chains of amino acids found.

Explanation:

A protein molecule is made from a long chain of these amino acids, each linked to its neighbor through a covalent peptide bond (Figure 3-1). Proteins are therefore also known as polypeptides. Each type of protein has a unique sequence of amino acids, exactly the same from one molecule to the next.

answer; a muscle cell, another neuron and a of the above

a- all cells come from pre-existing cells