Many diverse life forms inhabit Earth, each with its own set of unique traits. When examined on a microscopic scale, however, we find that all life on Earth is built from the same fundamental structural and functional unit: the cell. Cellular make-up, characteristics, and forms of life all differ. The integrity of the cell wall is one such crucial feature. Let’s dig deeper into the plant cell wall structure and function.
Definition of Cell Wall
A cell wall is the part of a cell that is not alive and covers the top layer. Its make-up depends on the organism and it lets things in and out. The cell wall keeps the contents of the cell from being exposed to the outside world. It also gives the cell and its parts shape, support, and protection. But this part of the cell is only found in eukaryotic organisms like plants, fungi, and a few prokaryotic organisms.
Fungi, like all multicellular organisms, have cell walls, but unlike those of bacteria and plants, fungi’s are made of chitin, a derivative of glucose that is also present in the exoskeletons of arthropods. And like plant cell walls, they help keep things from drying out and breaking down.
Microorganisms and other prokaryotic organisms also have cell walls. Peptidoglycans are massive polymers found in bacterial cell walls. To shield their cells from being lysed, prokaryotic organisms rely on cell walls. Cell walls in prokaryotes are bilayer structures, made up of two distinct parts: Peptidoglycans form an inner layer and an outer layer that is composed of lipoproteins and lipopolysaccharides.
Eukaryotic cells have a clear nucleus and a clear membrane around the nucleus. It also has organelles that are surrounded by a membrane, which are not found in prokaryotic cells. Another important thing to keep in mind is that other eukaryotic organisms, like animals, don’t have cell walls. Only plants do.
Structure of Cell Wall
Figure 1: Plant Cell Labelled Diagram
The term “cell wall” is used to describe the protective coating of a cell. This is close to where the cell membrane is. The plasma membrane is another name for it. The cell wall is present in every single plant cell, just as it is in the cells of bacteria, fungus, archaea, and algae. As a result of lacking cell walls, animal cells tend to be of odd sizes and shapes. The cell walls of various species also take on a variety of forms.
Typically, there are three levels to a plant’s cellular structure. The cell wall incorporates components like carbohydrates, cellulose, pectin, hemicellulose, and other minerals in lower amounts. These then link together with the structural proteins to form the cellular wall. The three layers composing the structure of the cell are:
Figure 2: Plant Cell Wall Structure and Function.
a. Primary cell wall
This is the first cell wall, which is closest to the inside of the cell. This cell wall is made of cellulose, which makes it easy for the wall to grow and stretch. Most of the primary cells are made of pectic polysaccharides and structural proteins. Most of the other layers are thicker than the primary cell wall, but it is thinner and more porous than most of the other layers.
b. The 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.
c. 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.
Cell Wall Components
The layers of the cell have a different composition; however, all of them contain similar components. These include: Cellulose, Matrix, polysaccharides, Proteins, Plastics.
Functions of Cell Wall
The plant cell wall provides definite shape, strength, and rigidity. It also provides protection against mechanical stress and physical shocks. It helps to control cell expansion due to the intake of water. It helps in preventing water loss from the cell. It is responsible for transporting substances between and across the cell. It acts as a barrier between the interior cellular components and environment.
FAQs on Plant Cell Wall Structure and Function
It’s the plant’s first line of defense against infections, and it supports the plant structurally as it grows.
The primary cell wall
The middle lamella
The secondary cell wall
The plant cell wall provides definite shape, strength, and rigidity.
It also provides protection against mechanical stress and physical shocks.
It helps to control cell expansion due to the intake of water.
It helps in preventing water loss from the cell.
The plasma membrane of a plant cell is surrounded by the cell wall, which gives the plasma membrane strength and protects it from mechanical and osmotic stress.