Why a Plant Cell Needs a Cell Wall: Key Functions and Benefits Explained

A plant cell has a cell wall for structure, support, and protection, and to keep its shape.

Functions

• Structure: cellulose gives rigid support.
• Protection from injury and pathogens.
• Shape: lets plants stand upright.
• Prevents bursting by controlling water intake (turgor).

Composition

Cellulose, hemicellulose and pectin.

Animals

Animal cells have no cell wall, just a cell membrane.

Thickness

Primary walls are thin. Secondary walls are thicker, with lignin.

Structure and composition

The cell wall sits outside the plasma membrane and is made mainly of cellulose, hemicellulose and pectin. Cellulose microfibrils are arranged in layers. Primary walls are thin (about 0.1 to 1 micrometer) and flexible, while secondary walls in wood cells add lignin and can be several micrometers thick.

• The wall provides shape, support and protection against pathogens, and resists turgor pressure that can reach about 5 to 10 atmospheres in some cells.
• Plasmodesmata are channels through the wall that link neighboring cells.
• Bacterial cell walls contain peptidoglycan and fungal walls contain chitin, so they differ from plant walls.

Animal cells and use

Animal cells have no wall, which allows flexible shapes and movement. Wood, cotton and paper come from plant cell walls. Cellulose is the most abundant organic polymer on Earth. Humans cannot digest cellulose, but it serves as dietary fiber. Lignin makes up about 20 to 30 percent of wood by dry weight.

Structure and composition

The plant cell wall is made mostly of cellulose microfibrils embedded in hemicellulose and pectin. A primary wall is flexible and a secondary wall, in wood, is strengthened with lignin. It supports the cell, prevents bursting from water pressure (turgor) and shapes the plant. Plasmodesmata are channels through the wall that link cells.

Contrast with animal cells

Animal cells lack walls and rely on a cytoskeleton and extracellular matrix. Fungi have walls made of chitin and bacteria have peptidoglycan walls. Cellulose is the most abundant organic polymer on Earth and is used for paper and textiles.

Cell wall layers

Plant cell walls have a middle lamella made of pectin that glues cells, a primary wall of cellulose, hemicellulose and pectin, and in some cells a lignified secondary wall. Cellulose microfibrils have a tensile strength comparable to steel by weight. Plant cells maintain turgor pressure of 0.3 to 1.0 MPa, similar to a car tire.

Roles in life and industry

Cell walls control cell expansion, defend against pathogens and set the shape of tissues. Wood is largely secondary cell walls, with lignin 20 to 30 percent. Humans use plant walls as dietary fiber, paper, cotton and biofuel. Fungal chitin and bacterial peptidoglycan walls are targets of antibiotics such as penicillin.

Based on data from the National Center for Biotechnology Information and standard plant biology texts