Question

1. what level is represented by a simple chain of amino acids? 2. which level involves folding into alpha - helices and beta - sheets? 3. which two levels describe the overall 3d shape?

Explanation:

1. The primary structure of a protein is the linear sequence of amino - acids.
2. The secondary structure of a protein involves local folding into alpha - helices and beta - sheets due to hydrogen bonding.
3. The tertiary and quaternary structures describe the overall 3D shape of a protein. Tertiary structure is the 3D shape of a single polypeptide chain, and quaternary structure is the 3D arrangement of multiple polypeptide chains.

Answer:

1. Primary Structure
2. Secondary Structure
3. Tertiary Structure, Quaternary Structure