While, the cell wall is a non-living structure. Both of them are present at the boundaries of the cells.
Their common role is to give protection to the whole cell and other organelles in the cell. Further both of them together form the cytoplasmic bridges.
These cytoplasmic bridges help in inter-cell communication and transfer.
Also both of them are involved partly in cell division and exist from birth to death of the cell. But there are many difference between Cell Membrane and Cell Wall which we will see in a table below.
Difference between Cell Wall and Cell Membrane.
Before we go into details, check the two cells below. One is of plant cell and other is animal cell. Plant cell has cell wall while animal cell has not wall.
|Features||Cell membrane||Cell wall|
|Distribution||Cell membrane is present in all types of cells. i.e human, animal, plant, bacterial etc.||Cell wall is Present in only plant cells and bacterial cells.|
|Living nature||Cell membrane is an organelle of the cell. And is outermost cover in animals and humans. It provides shape to cell which is flexible.||Cell wall is the outer non-living cover of the cell but not an organelle. It encloses cell membrane. It also provides a fixed shape.|
|Composition||It is a lipid bilayer. And is made of lipo-proteins.||This is made of pectin, chitin, lignin etc. In bacteria it is made of glyco-proteins, glyco-lipds|
|Ductility||This has the ability to contract. It is flexible to change the shape as needed.||Cell wall is rigid with fixed shape. Any pressure application can break the wall.|
|Communication||Cell membrane has receptors to receive signals from external chemicals.||Cell wall lacks any receptors.|
|Appendages||In Bacteria, cell membrane gives rise to flagella (movement) and pilli (reproduction) like structures.||While cell wall facilitates flagella and pilli through small apertures.|
|Structural changes||It is of the same thickness in the whole life time of the organism.||The wall grows in thickness over time. Further, it occupies whole cell in plant as the cell ages and dies.|
|Physiological support||The membrane is permeable and controls the movement of substance into and outside the cell. That is, it can allow water and other substance to pass through selectively.||The cell wall is semi-permeable. It allows passage of substances with size of 30-60kD.|
|Role in cell||Cell membrane has functions like permeability, signal reception, motility (amoeba), conduction (nerve cell), cell division, sexual reproduction etc.||Cell walls only function is protection from external harsh environment.|
|Changes||Cell membrane requires nutrition from cell. So it shrinks during fast and drought conditions.||While cell wall is mere deposit of substances. So it does not need nutrition but mere deposition in case of damage.|
As you have learnt till now, cell wall and cell membrane are both meant to cover and protect the cell. But not all cells have both of them. Cell membrane is present in all the cells. While cell wall is present in cells like that of bacteria, algae, fungi and plant cells. The difference between the cell membrane and cell wall are quite few yet worth reading.
3. Role in physiology
4. Role in disease.
5. In stress and after death
Cell membrane. This is mostly made of phospholipids, cholesterol, carbohydrates, proteins in most animal cells. In other cells like that of plants and bacteria, there are few changes instead of cholesterol, there is sterol and lipopolysacharides.
Cell wall on the hand varies in composition in different organisms. In bacteria, it is made of peptidoglycans, lipopolysacharides, lipoproteins etc. In algae, the cell wall is composed of glycoproteins and polysaccharides such as carrageenan and agar. In plant cells, the cell wall is made of cellulose, hemicellulose, pectin etc. In older cells, there is addition of even lignin in the cell wall to give rigidity. In animals, as mentioned earlier there is no cell wall.
Structure: The cell membrane is a lipid bi-layer in most cell types. It is fluidic and adjusts according to the environment conditions.
Cell wall is rigid and is made of chain like structures of proteins and carbohydrates.
Role in physiology: Both cell wall and cell membrane are involved in cellular physiology to certain extent. However, cell wall has comparatively little role than cell membrane.
Cell membrane helps in transport into and outside the cell. For this, it has transport proteins and other channels to facilitate the process.Further, the plasma membrane has receptors to receive signals from neurotransmitters, hormones and other chemicals.
Cell wall, is mostly impermeable except for water molecules and ions. Instead, the cell wall of adjacent cells in plants form cytoplasmic bridges called plasmadesmata. Through these plasmadesmata, the required cell constituents get exchanged in between cells.
Role in disease:
Defects or dysfunction in cell membrane can lead to diseases. The cell membrane is involved in movement of ions and other substances. Defects in its function would lead to imbalance in nutrition like aspects in cell. If this problem exists in many cells, the whole organ can get damaged. Alzheimer’s disorder is one of the disease caused by defects in plasma membrane.
In stress: During the conditions of stress or harsh environmental conditions, both act in their own ways to save the cell.
In case of plant cells, the cell wall prevents drying of cell by inhibiting the evaporation of water from cell.
Cell membrane forms blebs under the conditions of stress. Sometimes these blebs are act to protect the cell.
After cell death, cell membrane is completely digested like rest of the cell. But the walls are not always destroyed. In plants, these cell walls are thickened to form channels like xylem and phloem. Xylem helps in upward movement of water and other nutrients. While phloem helps in downward movement of carbohydrates and other substances from the leaves.
The presence of cell wall makes a huge difference in targeting bacteria in human and animal infections. This is used as a target to kill them specifically by use of anti-biotics without damage to animal cells. As per taxonomy and evolution point of view, presence of cell wall is a primitive aspect.
With advancement of life, the cell wall has become obsolete.
Check out The Functions of Cell wall in plant cell.
But the other argument is for plants cell wall is essential. Because, since they are non-motile, they need cell wall to protect themselves from harsh condition. But animals on other hand can run away from those conditions or make alternatives for protection like hiding in safety or covering themselves. So they may not need cell wall. Also in the most primitive organism like bacteria, there is further protection on the cell wall in the form of capsule. This is also an additional layer developed by them in time of drought conditions.
So we can conclude that cell wall is a mere protection layer while the membrane is both a protective, structural as well as a physiological requirement.