Question

a scientist is comparing the outer layer of an onion cell to the outer layer of a human skin cell. what is unique about the outer layer of the onion cell compared to the skin cell?
it contains proteins.
it contains cellulose.
it contains carbohydrates.
it is selectively permeable.

Explanation:

Onion cells are plant cells. Plant cells have a cell wall made of cellulose outside the cell membrane. Human skin cells (animal cells) do not have a cell wall. Both plant and animal cells have cell membranes (which are selectively permeable and contain proteins and carbohydrates). So the unique component in the outer layer of the onion cell compared to the skin cell is cellulose.

Answer:

It contains cellulose.