Human cells do not have cell walls. Cell walls are multilayered structures that are unique to plants, bacteria, fungi and some protozoa. However, only plant cell walls are made out of cellulose.
Cellulose is a long chain of complex sugar molecules that gives plants protection and support. According to Indian University, cell walls provide protection from insects and pathogens, such as bacteria, viruses and fungi. They also provide mechanical support to allow plants to grow upright and hold up their leaves to the light.
Cell walls also help plants to keep their shape. While humans and animals have skeletons to support and keep them in shape, plants use cell walls to influence a plant cell’s development and determine its shape.
Cell walls are not solid fortresses that surround the cells. There are small pores around the cell wall called plasmodesmata, which allow water, nutrients and wastes to pass through from cell to cell.