Protein Structure
Complete the following sentences to describe the various levels of protein structure. Then place the sentences in order with the simplest level of organization first.

Primary
Secondary
Tertiary
Quaternary
Amino acids
Nucleotides

1. A sequence of amino acids strung together in a strand forms a ______ structure.
2. Once amino acids begin to form bonds with one another to create helical or sheet-like formations, a _______ structure is formed.
3. The final folded three-dimensional shape of a polypeptide is referred to as a protein's ________ structure.
4. When two or more polypeptides bond together into a working protein, it represents a _______ structure.