The diagram is a model of the structure of a certain type of cell. Like all models, the diagram is accurate in many ways but does not show all features or properties. For example, the structure labeled 2 may take on a variety of sizes, depending on the amount of water available to the cell. The structure labeled 4 occurs in different numbers in different comples of the
cell. It has a characteristic green color and is involved in energy transformation.
What is the chemical composition and purpose of structure 3?
O It is made of chitin, and acts to protect and support the cell.
It is made of DNA and proteins, and acts to control cell activities.
It is made of cellulose and other carbohydrates, and acts to protect and support the cell.
It is made of a lipid bilayer and proteins and acts to allow passage of certain substances in and out of the cell.