Answer:
respiration, waste production, food intake, cells, breathing
The answer is; Beads of different color joined together on a piece of string
Primary structure of a protein is right after it has been translated from an mRNA by a ribosome. It is linear and has not yet been folded into a functional protein. The beads in the item represent amino acids joined together by peptide bonds.
There are so many examples for that in different areas, like TPBA experiment carried out in our lab recently.Here's one link: http://www.alfa-chemistry.com/tpba-cas-172285-72-2-item-294462.htm