Cell Wall and Cell Membrane

A cell is the structural and functional working unit of life and also been described as building blocks and fundamental unit of an organism.  The term cell was first identified by an English philosopher Robert Hooke in the year 1665. The shape and size of the cells vary according to their functions and compositions. There are different types of cells and can be differentiated based on the presence and absence of few cell organelles.

Cell Wall

Cell Wall

The cell wall is present only in plants, fungi, and bacteria. The image above represents a plant cell wall

The cell wall is the outermost covering of plant cells. It is present outside the cell membrane and is tough, flexible and sometimes rigid in its texture. It is mainly composed of cellulose,  long fibres of carbohydrates including hemicellulose, lignin, and pectin.

The main functions of the cell wall

  1. Protecting the cell against physical damage and invading pathogens.

  2. Regulate and controls the direction of cell growth.

  3. Providing the strength, structural support and maintaining the shape of the cell.

  4. Functions as a storage unit by storing carbohydrates for use in plant growth, especially in seeds.

  5. It acts as a selectively permeable membrane by allowing the entry of small molecules to pass through it.

Explore More: Plant cell

Cell Membrane

Cell Membrane

Cell Membrane is present in all organisms including plants

The cell membrane is also known as the plasma membrane. It is the outermost covering of animal cells. It is a semi-permeable membrane composed of lipids and proteins. The main functions of the cell membrane include:

  1. Protecting the integrity of the interior cell.

  2. Providing support and maintaining the shape of the cell.

  3. Helps in regulating cell growth through the balance of endocytosis and exocytosis.

  4. The cell membrane also plays an important role in cell signalling and communication.

  5. It acts as a selectively permeable membrane by allowing the entry of only selected substances into the cell.

Also Read: Animal Cell

Difference between Cell Wall and Cell Membrane

One of the fundamental difference between the plasma membrane and the cell wall is in the type of organisms that they are found. The cell wall is present only in plants and the cell membrane is present in every living organism including plants.

CELL WALL

CELL MEMBRANE

Present only in plants, and in some fungi, bacteria, algae. Present in all types of cells, in humans, animals, plants, bacteria, etc.
It is the outer non-living part of the cell but not an organelle which encloses cell membrane and provides a fixed shape. It is an outermost, flexible, living organelle of the cell which provides shape to the cell.
It is made up of pectin, chitin, lignin, glycol proteins, glycolipids, sugar, and cellulose. It is a lipid bilayer. And is composed of lipoproteins and carbohydrates.
The structure of the cell wall is 20- 80nm in thickness The structure of the cell membrane is 7.5–10 nm in thickness
It is the thick and rigid structure with a fixed shape. It is thin and delicate structure. It is flexible to change the shape as needed.
It protects the cell from the external environment. It protects and maintains the internal environment of the cell.
The cell wall is elastic. The cell membrane is non-elastic.
The cell wall is metabolically inactive The cell membrane is metabolically active.
Cell wall lack receptors. The cell membrane has receptors to receive signals from external chemicals.
The cell wall grows in thickness over time. Further, it occupies the whole cell in the plant as the cell ages and dies. It is of the same thickness for the whole lifetime of the organism.
The cell wall is semi-permeable. It allows passage of substances with the size of 30-60 kD. The membrane is permeable and controls the movement of the substance into and outside the cell. That is, it can allow water and other substance to pass through selectively.
Functions include protection from the external environment. Functions include permeability, signal reception, motility conduction, cell division, sexual reproduction etc.

Also Read: Difference Between Plant cell and Animal cell

Conclusion

The cell wall and cell membrane are two organelles that are integral in every living organism. However, the latter is found only in plants, fungi and in some bacteria. Traditionally, a cell well is defined as the layer of polysaccharides that exists outside the plasma membrane. It is rigid and serves structural and supportive functions. On the other hand, the cell wall in fungi is made from another material called chitin, which is also found in the exoskeletons of arthropods.

The cell membrane is present in all living organisms, including plants. It is the outermost layer of the cell and encloses other cellular organelles within in. Unlike the cell wall, the cell membrane is flexible and its shape can be changed as needed. Also, it is metabolically active and has increased membrane permeability.

Cell Wall and Cell Membrane – Important Questions

1. What is the main function of the cell wall?

The cell wall is the outer most layer in a plant cell. It provides structural support and rigidity for the plant body. Furthermore, it is a selectively permeable membrane and filters molecules that pass through the cell.

2. What is the function of the cell membrane?

Unlike the cell wall, the cell membrane is present in all living organisms, including plants. The main role of the cell membrane is to provide protection to the cell from its surroundings. It is also more permeable than the cell wall and metabolically active.

3. Are cell walls and cell membranes the same thing?

Cell walls are distinctly different from cell membranes. For instance, the cell wall is present only in plants, fungi and some bacteria. The cell membrane, on the other hand, is present in all living organisms including plants.

4. What is the role of the plasma membrane?

The cell membrane is also called the plasma membrane. It provides protection for the cell and its cellular components from the external environment.

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Practise This Question

Which of the following pairs of cell organelles work together to package macromolecules?

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