Question

Do all cells have a primary cell wall composed of cellulose?

Answer 1

No, not all cells possess a cell wall composed of cellulose.

A cell wall is a rigid, semi-permeable protective layer which is found in some cell types including the cells of plants, fungi, bacteria, algae, some Archaea and some Protists. This extra outer covering is positioned outside the cell membrane (plasma membrane) in them. Animal cells and some Protists do not have a cell wall. The major functions of cell wall are protecting the cell, maintaining the cell structure, and to filter molecules that pass in and out of the cell.

Cell wall composition varies in different organisms. In plants and some Protists, the cell wall is composed primarily of strong fibers of the carbohydrate polymer cellulose. Bacterial cell walls are composed of a sugar and amino acid polymer called peptidoglycan. The main components of fungal cell walls are chitin, glucans, and proteins.

In plant cells, the cell wall can be differentiated as primary and secondary cell walls. All plant cells have a primary cell wall composed mainly of cellulose. The primary wall is the cellulose-containing, thin, flexible layer in actively dividing and growing cells. The secondary cell wall is formed inside the primary cell wall, later in fully grown cells. It is found in between the primary cell wall and the cell membrane. Secondary cell wall is not found in all plant cell types. Some cells, such as the conducting cells in xylem, possess a secondary wall, which is durable due to deposition of lignin.