Cell Wall - Plant Anatomy

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Introduction to Cell Wall

There are innumerous life forms on earth, each having specific characteristics and features. But, at the microscopic level, they are all composed of similar functionalities when we observe them. All of them contain the basic structural and fundamental unit of life. This is called the cell. 


However, all cells are not similar. The cells have varying compositions based on the type of life form it exists in. One of these very important characteristics is the cell wall. It contains various components and has a defined structure. Let us help you know more about it and its existence in various life forms. 


What is a Cell Wall?

A cell wall is a non-living component. It covers the outermost layer of the cell-protecting it from the outer environment. The composition of the cell wall varies based on the organism. It has a permeable nature, separating the interior content of the cell from exterior components. The cell wall is responsible for providing support, protection, and shape to the cell. It is present only in fungi, eukaryotic plants, and very few prokaryotes. 


The cell wall in fungi is composed of chitin, which is a glucose derivative. The cell wall is also found in the exoskeleton of the arthropods. 


The prokaryotic organisms, including bacteria, have cell walls. But, their chemical composition is different as compared to that of fungi and plants. There are two layers present in the cell walls of prokaryotes. These include:

  • Inner Layer: It is made of peptidoglycans

  • Outer Layer: It is made up of lipopolysaccharides and lipoproteins

Only plants contain cell walls. These are absent in eukaryotic organisms. The eukaryotic cells have a proper nucleus along with a nuclear membrane. 


Structure of the Cell Wall

The outer covering of the cell is called the cell wall. This is present adjacently with the cell membrane. It is also called the plasma membrane. All plant cells contain the cell wall like bacteria, fungi, archae, and algae. Animal cells do not contain cell walls which lead to their irregular shape. Alongside, the shape of cell walls is different for different organisms. 


The arrangement of plant cells is mainly in the form of 3 layers. The cell wall comprises elements like carbohydrates, cellulose, pectin, hemicellulose, and other minerals in smaller amounts. From these, a network is formed with the structural proteins leading to cell wall formation. The three layers forming the structure of the cell are:

  • Primary cell wall

  • The middle lamella

  • Secondary cell wall

Primary Cell Wall:

This is the first cell wall which is situated closest to the inside of the cell. This cell wall is formed of cellulose which allows the wall the stretch and grows easily. Most of the primary cells contain structural proteins and pectic polysaccharides. The primary cell wall is thinner than most other layers and is comparatively permeable than others. 


Middle Lamella:

It is the outermost layer of the cell wall. It is like an interface between the neighboring cells, gluing them together. The middle lamella is mainly composed of pectins. Along with this, other substances like proteins and lignin can also be found in this layer. 


Secondary Cell Wall:

After the cell grows completely, this wall is formed in the inner part of the primary cell wall. Certain cells are formed of lignin and cellulose, providing additional rigidity and waterproofing to the cells. Further, the rectangular shape of the cell is also provided by this layer. This layer provides permeability, and it’s also the thickest layer. 


Functions of the Cell Wall

The cell wall is one of the most integral components of a cell wall. It performs several important functions, the list of which is as follows:

  • The cell wall of the plants provides rigidity, structure, and strength to the cell.

  • Protection is provided by the cell wall against the physical shocks and mechanical strengths.

  • Due to water intake, the cells start expanding. The cell wall prevents and controls the expansion of the cell.

  • Prevention of water loss happens because of the presence of a cell wall.

  • Transportation of substances across and between the cell takes place through the cell wall.

  • The cell wall is like a barrier between the external environment and the internal components of the cell.

Components of a Cell Wall

The layers of the cell have a different composition; however, all of them contain similar components. These include:

  • Cellulose

  • Matrix polysaccharides

  • Proteins

  • Plastics

FAQ (Frequently Asked Questions)

1. What is the Importance of Bacterial Cell Walls?

In bacteria, the cell wall serves to keep the cell shape intact and is quite essential for its survival. The antibiotics work on the principle of targeting the cell wall, leading to lysis. This further explores the contents of the cell, which destroys it and eventually, the cell dies. 

2. Apart from Bacteria, Which Organisms Contain a Cell Wall?

Along with plants, prokaryotic organisms also contain cell walls. The cell wall of these organisms is made of peptidoglycan. This is formed of amino acids and sugar. Cell walls are also contained in fungi. These cell walls are formed from elements called chitin, which is a complex carbohydrate.

3. Give the Definition of a Cell Wall and Its Functions.

The cell wall is defined as the rigid layer which provides support to the structure of the cell. Alongside, cell walls also protect the internal components of the cell. The main function of the cell wall is the provision of a layer that allows the elements to pass through the cell from the permeable membrane that it has. 

4. What are the Names of the 3 Layers of the Cell Wall?

A plant cell contains 3 layers in the cell wall: the primary cell wall, middle lamella, and the secondary cell wall.