Difference between Plasma Membrane and Cell Wall

The cell is the fundamental structural, biological and functional unit of all living organisms. It is also known as building block of life. The numbers of cells vary from species to species. Each cell is enclosed by a membrane and composes of proteins and nucleic acids. In bacteria, fungi, algae and plant cell, the outer most covering of the cell is known as cell wall which covers the cell membrane. The cell wall is absent in all types of animal cell.  The cell wall makes the outermost boundary of the cell (if present) over the plasma membrane. The cell membrane is also known as biological membrane, plasma membrane or plasma lemma. It is present in almost all types of cells. The cell membrane is semi permeable which allows the passage of certain substances through them.

Chemical Composition of the Cell Wall 

In most of the plant cells, the cell wall is composed of the following components:

• Cellulose
• Hemicellulose
• Pectin
• Lignin
• Protein
• Chitin  (in fungal cell) and
• Peptidoglycan- protein-lipid polysaccharide (in bacterial cell);

Plasma membrane: Detailed Diagram

Chemical Composition of Plasma Membrane

• Proteins: integral proteins, lipid anchored proteins, peripheral proteins;
• Carbohydrates: glycoprotein, sugars like galactose and sialic acid;
• Lipids: glycolipids, phospholipids and steroids;

Functions of Plasma Membrane

• Plasma membrane separates the components inside the cell from the outside environment.
• It provides support to the cytoskeleton of the cell.
• It gives the shape to the cell.
• It helps to form of tissues.
• It helps in communication with other cells.
• It acts as a molecular signals;
• It allows the passage of certain molecules through them.
• It contains protein receptors which receives signals from the other cells and the environment.
• It helps to regulate cell growth by making the balance of endocytosis and exocytosis.

Diagram of Plant Cell Wall

Functions of Cell Wall

• It gives rigidity and strength to the cell.
• LIt protects the cell from external environmental stress and other mechanical forces.
• It maintains cell morphology;
• It helps to prevent large sized molecules to enter into the cell.
• It prevents the cells from toxins.
• It maintains the osmotic pressure of the cell.

Difference between Plasma Membrane and Cell Wall

Plasma Membrane	Cell Wall
It is a delicate and thin structure which is about 5-10 nm wide.	It is a thick and rigid structure which is 4-20 µm wide.
It is observable under electron microscope.	It is observable under light microscope.
It helps in the passage of molecules and protects the protoplasm.	It helps in providing shape and rigidity to the cell.
It is present both in animal and plant cells.	It is found in bacteria and fungus and plant cell.
It is present outside the protoplasm (cytoplasm) of all living cells.	It is present outside the plasma membrane of a plant cell.
It is a living material of a cell.	It is a non-living material of a cell.
It is composed of lipid, protein and carbohydrates.	It is composed of cellulose(plant), chitin(fungi) and peptidoglycan (bacteria).
It is thin and elastic.	It is comparatively thick and rigid.
It has some specialized structures like micrivilli and desmosomes.	Between the adjacent cells there are cytoplasmic bridges known as plasmodesmata.
It is semi permeable.	It is completely permeable.
It has phagocytic and pinocytic functions.	It has no phagocytic or pinocytic functions.
Cell membrane shows no pattern of ornamentation.	Cell wall shows different patterns of ornamentation.
It needs proper nutrition to survive.	It doesn’t need any nutrition from cell but deposition instead.
The plasma membrane is non-elastic.	The cell wall is elastic.
It is metabolically active and living.	It is metabolically inactive and non-living.
It protects the cell from the external environment.	It guards and maintains the internal environment of the cell.
Plasma membrane has receptors which help to make communication between cells to cell to receive signals from external chemicals.	Cell wall does not have any receptors.
It remains same thickness throughout its life.	Thickness does not remain constant; it grows  with life.

Also read: Detailed Structure of Plasma Membrane and its Functions