Answer:
1. The space-filling model is used when one wants to show the three-dimensional shape of a protein, comprising all of the atoms constituting it.
2. A simplified diagram is used when one desires to show the general shape of a protein, along with certain essential functional details like coils and folds.
3. A ribbon model is used when one desires to demonstrate the three-dimensional shape of a protein, comprising the backbone composition, coils, and folds.
4. A simple shape is used when one desires to demonstrate a generalized protein in which the focus is on the function of the protein in spite of its structure.
5. A wireframe model is used if one wants to demonstrate the three-dimensional shape of a protein by showing the amino acid side chains and their associations.