What is a cell wall in plants?

The cell wall is a specialized structure outside the cell membrane of plant cells, setting them apart from animal cells. Plant cell walls are composed of cellulose , unlike the peptidoglycan found in bacteria or chitin in fungi. The cell wall's functions include protecting the cell, facilitating the circulation of nutrients, providing building blocks for plant structures, and storing molecules that detect pathogens and control tissue development. Although often seen as mainly structural, the cell wall is critical to plant life.

Where is the cell wall located in a plant cell?

The cell wall is a specialized structure that is outside the cell membrane and surrounds every plant cell. It is a type of extracellular matrix that gives plant cells their unique characteristics. All plant cell walls have a middle lamella and a primary cell wall, and some also have a secondary cell wall. The middle lamella is like cement between the primary walls of neighboring cells. The primary wall contains cellulose and is created in growing and dividing cells. Secondary cell walls give the majority of a plant's mechanical support and are responsible for the mechanical qualities found in wood.

What is the cell wall made of?

Plant cell walls are composed of cellulose fibers embedded in a matrix of polysaccharides and structural glycoproteins. The two major classes of matrix polysaccharides are hemicelluloses and pectic polysaccharides, or pectins. Hemicelluloses consist of glucose molecules arranged with short side chains, which bind to cellulose fibrils, preventing them from uncontrolled adhesion and regulating primary cell wall expansion during growth. Pectic polysaccharides are negatively charged and bind to cations. Calcium ions cross-link galacturonic acid residues, creating the semirigid gel properties of the cell wall matrix. Small amounts of protein are also present in plant cell walls and serve important functions. Hydroxyproline-rich glycoproteins, such as extensin, are structural proteins that become cross-linked into a mesh, while other enzymes cross-link extensin, lignin, cutin, and suberin molecules into networks. Lignin adds compressive strength and stiffness to the plant cell wall and also waterproofs the cell wall, facilitating water transport in xylem tissues.

How does the cell wall help protect and support a plant?

The plant's cell wall is a specialized extracellular matrix that surrounds each plant cell, providing mechanical protection and a chemically buffered environment. It facilitates the circulation of water, minerals, and nutrients and provides rigid building blocks for structures such as leaves and stems. Composed of cellulose, the cell wall has two layers: the middle lamella and the primary cell wall. The middle lamella cements the primary walls of adjacent cells, while the primary wall, containing cellulose, is formed during cell division and growth. Many cells also produce a secondary cell wall for mechanical support and other properties. The cell wall's architecture includes cellulose fibers embedded in a matrix of polysaccharides and structural glycoproteins.

How is the plant cell wall different from an animal cell membrane?

Plant cells and animal cells differ significantly because plant cells feature a cell wall, which animal cells lack. The cell wall is a specialized extracellular matrix that surrounds each plant cell, providing mechanical protection, a chemically buffered environment, and structural support, distinguishing them from animal cells. Plant cell walls are composed of cellulose , setting them apart from other organisms like bacteria and fungi, which have peptidoglycan and chitin, respectively. Animal cells are bound by a cell membrane (or plasma membrane), a thin barrier that separates the interior of the cell from its external environment. The cell membrane's primary function is to protect the cell by keeping wanted material in and unwanted material out. It also contains proteins that transport nutrients and waste and help cells connect with other materials.

What are the main layers of the plant cell wall, and what does each layer do?

The plant cell wall has three main layers: * Middle lamella This outermost layer cements together the primary walls of adjacent plant cells. * Primary cell wall This layer contains cellulose and is formed while the cell divides and grows. It's thinner and less rigid than secondary walls, which allows for cell expansion. Turgor pressure against the cell wall gives it a supportive role, similar to air pressure stiffening a tire. * Secondary cell wall Not all plant cells have this additional, rigidifying layer. Secondary cell walls give the plant mechanical support and provide the properties prized in wood. In addition to these layers, plasmodesmata are microscopic cytoplasmic canals that pass through plant-cell walls, connecting plant cells and enabling direct communication between them.

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Cutaway illustration of a plant cell showing labeled internal structures including the nucleus, nucleolus, chloroplast, mitochondrion, vacuole, endoplasmic reticulum, ribosomes, Golgi apparatus, cell wall, and other key organelles.

How Are Plant Cells Different from Animal Cells?

Two structural diagrams compare glucose and cellulose: on the left, a single glucose molecule in a ring form, and on the right, a cellulose polymer made of repeating glucose units linked in a chain.

Small brown mushrooms growing at the base of a tree.

Illustration comparing three cell types: a round animal cell and an irregularly shaped plant cell, both showing labeled organelles, and an elongated bacteria cell with labeled structures such as flagella and capsule.

Eukaryotic vs. Prokaryotic Cells: Key Differences Explained

cell wall

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L. Andrew Staehelin

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Last updated

Oct. 25, 2026 •History

Top Questions

What is a cell wall in plants?
The cell wall is a specialized structure outside the cell membrane of plant cells, setting them apart from animal cells. Plant cell walls are composed of cellulose, unlike the peptidoglycan found in bacteria or chitin in fungi.

The cell wall's functions include protecting the cell, facilitating the circulation of nutrients, providing building blocks for plant structures, and storing molecules that detect pathogens and control tissue development. Although often seen as mainly structural, the cell wall is critical to plant life.
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Where is the cell wall located in a plant cell?
The cell wall is a specialized structure that is outside the cell membrane and surrounds every plant cell. It is a type of extracellular matrix that gives plant cells their unique characteristics.

All plant cell walls have a middle lamella and a primary cell wall, and some also have a secondary cell wall. The middle lamella is like cement between the primary walls of neighboring cells. The primary wall contains cellulose and is created in growing and dividing cells. Secondary cell walls give the majority of a plant's mechanical support and are responsible for the mechanical qualities found in wood.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What is the cell wall made of?
Plant cell walls are composed of cellulose fibers embedded in a matrix of polysaccharides and structural glycoproteins. The two major classes of matrix polysaccharides are hemicelluloses and pectic polysaccharides, or pectins. Hemicelluloses consist of glucose molecules arranged with short side chains, which bind to cellulose fibrils, preventing them from uncontrolled adhesion and regulating primary cell wall expansion during growth. Pectic polysaccharides are negatively charged and bind to cations. Calcium ions cross-link galacturonic acid residues, creating the semirigid gel properties of the cell wall matrix.

Small amounts of protein are also present in plant cell walls and serve important functions. Hydroxyproline-rich glycoproteins, such as extensin, are structural proteins that become cross-linked into a mesh, while other enzymes cross-link extensin, lignin, cutin, and suberin molecules into networks. Lignin adds compressive strength and stiffness to the plant cell wall and also waterproofs the cell wall, facilitating water transport in xylem tissues.
4 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How does the cell wall help protect and support a plant?
The plant's cell wall is a specialized extracellular matrix that surrounds each plant cell, providing mechanical protection and a chemically buffered environment. It facilitates the circulation of water, minerals, and nutrients and provides rigid building blocks for structures such as leaves and stems.

Composed of cellulose, the cell wall has two layers: the middle lamella and the primary cell wall. The middle lamella cements the primary walls of adjacent cells, while the primary wall, containing cellulose, is formed during cell division and growth. Many cells also produce a secondary cell wall for mechanical support and other properties. The cell wall's architecture includes cellulose fibers embedded in a matrix of polysaccharides and structural glycoproteins.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How is the plant cell wall different from an animal cell membrane?
Plant cells and animal cells differ significantly because plant cells feature a cell wall, which animal cells lack. The cell wall is a specialized extracellular matrix that surrounds each plant cell, providing mechanical protection, a chemically buffered environment, and structural support, distinguishing them from animal cells. Plant cell walls are composed of cellulose, setting them apart from other organisms like bacteria and fungi, which have peptidoglycan and chitin, respectively.

Animal cells are bound by a cell membrane (or plasma membrane), a thin barrier that separates the interior of the cell from its external environment. The cell membrane's primary function is to protect the cell by keeping wanted material in and unwanted material out. It also contains proteins that transport nutrients and waste and help cells connect with other materials.
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What are the main layers of the plant cell wall, and what does each layer do?
The plant cell wall has three main layers:
* Middle lamella This outermost layer cements together the primary walls of adjacent plant cells.
* Primary cell wall This layer contains cellulose and is formed while the cell divides and grows. It's thinner and less rigid than secondary walls, which allows for cell expansion. Turgor pressure against the cell wall gives it a supportive role, similar to air pressure stiffening a tire.
* Secondary cell wall Not all plant cells have this additional, rigidifying layer. Secondary cell walls give the plant mechanical support and provide the properties prized in wood.

In addition to these layers, plasmodesmata are microscopic cytoplasmic canals that pass through plant-cell walls, connecting plant cells and enabling direct communication between them.
4 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

cell wall, specialized form of extracellular matrix that surrounds every cell of a plant. The cell wall is responsible for many of the characteristics that distinguish plant cells from animal cells. Although often perceived as an inactive product serving mainly mechanical and structural purposes, the cell wall actually has a multitude of functions upon which plant life depends. Such functions include: (1) providing the living cell with mechanical protection and a chemically buffered environment, (2) providing a porous medium for the circulation and distribution of water, minerals, and other small nutrient molecules, (3) providing rigid building blocks from which stable structures of higher order, such as leaves and stems, can be produced, and (4) providing a storage site of regulatory molecules that sense the presence of pathogenic microbes and control the development of tissues.

Certain prokaryotes, algae, slime molds, water molds, and fungi also have cell walls. Bacterial cell walls are characterized by the presence of peptidoglycan, whereas those of Archaea characteristically lack this chemical. Algal cell walls are similar to those of plants, and many contain specific polysaccharides that are useful for taxonomy. Unlike those of plants and algae, fungal cell walls lack cellulose entirely and contain chitin. The scope of this article is limited to plant cell walls.

Mechanical properties

plant cellOnion skin cells under a microscope.

All cell walls contain two layers, the middle lamella and the primary cell wall, and many cells produce an additional layer, called the secondary wall. The middle lamella serves as a cementing layer between the primary walls of adjacent cells. The primary wall is the cellulose-containing layer laid down by cells that are dividing and growing. To allow for cell wall expansion during growth, primary walls are thinner and less rigid than those of cells that have stopped growing. A fully grown plant cell may retain its primary cell wall (sometimes thickening it), or it may deposit an additional, rigidifying layer of different composition, which is the secondary cell wall. Secondary cell walls are responsible for most of the plant’s mechanical support as well as the mechanical properties prized in wood. In contrast to the permanent stiffness and load-bearing capacity of thick secondary walls, the thin primary walls are capable of serving a structural, supportive role only when the vacuoles within the cell are filled with water to the point that they exert a turgor pressure against the cell wall. Turgor-induced stiffening of primary walls is analogous to the stiffening of the sides of a pneumatic tire by air pressure. The wilting of flowers and leaves is caused by a loss of turgor pressure, which results in turn from the loss of water from the plant cells.

Components

Although primary and secondary wall layers differ in detailed chemical composition and structural organization, their basic architecture is the same, consisting of cellulose fibres of great tensile strength embedded in a water-saturated matrix of polysaccharides and structural glycoproteins.

Cellulose

Cellulose consists of several thousand glucose molecules linked end to end. The chemical links between the individual glucose subunits give each cellulose molecule a flat ribbonlike structure that allows adjacent molecules to band laterally together into microfibrils with lengths ranging from two to seven micrometres. Cellulose fibrils are synthesized by enzymes floating in the cell membrane and are arranged in a rosette configuration. Each rosette appears capable of “spinning” a microfibril into the cell wall. During this process, as new glucose subunits are added to the growing end of the fibril, the rosette is pushed around the cell on the surface of the cell membrane, and its cellulose fibril becomes wrapped around the protoplast. Thus, each plant cell can be viewed as making its own cellulose fibril cocoon.

Mechanism of cellular autophagy, illustration for Nobel Prize Award in Medicine 2016. 3D illustration showing fusion of lysosome with autophagosome containing microbes and molecules.

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Matrix polysaccharides

The two major classes of cell wall matrix polysaccharides are the hemicelluloses and the pectic polysaccharides, or pectins. Both are synthesized in the Golgi apparatus, brought to the cell surface in small vesicles, and secreted into the cell wall.

Hemicelluloses consist of glucose molecules arranged end to end as in cellulose, with short side chains of xylose and other uncharged sugars attached to one side of the ribbon. The other side of the ribbon binds tightly to the surface of cellulose fibrils, thereby coating the microfibrils with hemicellulose and preventing them from adhering together in an uncontrolled manner. Hemicellulose molecules have been shown to regulate the rate at which primary cell walls expand during growth.

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The heterogeneous, branched, and highly hydrated pectic polysaccharides differ from hemicelluloses in important respects. Most notably, they are negatively charged because of galacturonic acid residues, which, together with rhamnose sugar molecules, form the linear backbone of all pectic polysaccharides. The backbone contains stretches of pure galacturonic acid residues interrupted by segments in which galacturonic acid and rhamnose residues alternate; attached to these latter segments are complex, branched sugar side chains. Because of their negative charge, pectic polysaccharides bind tightly to positively charged ions, or cations. In cell walls, calcium ions cross-link the stretches of pure galacturonic acid residues tightly, while leaving the rhamnose-containing segments in a more open, porous configuration. This cross-linking creates the semirigid gel properties characteristic of the cell wall matrix—a process exploited in the preparation of jellied preserves.

cell wall

Mechanical properties

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Components

Cellulose

Matrix polysaccharides