The correct answer is option 1 - cell wall. Cellulose is a complex carbohydrate that serves as the main structural component of plant cell walls. It is made up of long chains of glucose molecules that are linked together. The cell wall provides rigidity and support to plant cells, allowing them to maintain their shape and resist mechanical stress. It acts as a protective barrier and regulates the movement of substances in and out of the cell. Cellulose is found in the primary cell wall, which is the first layer formed during cell growth, as well as in the secondary cell wall, which is a more rigid and durable layer found in some specialized plant cells. Cellulose is not present in the cell membrane, which is a lipid bilayer that surrounds the cell and controls the exchange of materials. It is also not found in the body wall of insects, which is composed of a different substance called chitin.