Ascientist is comparing that outer layer of an onion cell to the outer layer of a human cell what is unique about the outer layer of the onion cell compared to the skin cell

The function of a cell wall has the same function of the cell membrane; it protects the cell. Cell wall is made up of cellulose that is only present in plant cells. Cellulose is a sugar that has a sheet like structural carbohydrate. It is rigid that is used for support and provides protection to the plant cell from damage. They cannot be dissolved in water. An example is if you eat food that contains mostly of leaves. You will observe that you will eliminate the same material as when you it. That is because our human body does not have the enzyme that dissolves the cellulose.

An autotrophic protist - they can perform photosynthesis and mainly consist of unicellular algae. they can be divided into number of systematic group according to the shape of their cell and the type of photosynthetic pigments they use.