Cell Wall vs Cell Membrane
Cell membrane (plasma membrane) and cell wall are the outermost layers of the cell that separate cell organelles from its external environment. These special layers provide shape to the cells and mechanical barrier for the protection of internal cell organelles. However, unlike the cell membrane that is present in all types of cells, cell wall is present in plant, fungi and most protists cells only, not in animal cells. This article will discuss cell wall and cell membrane in animal and plant cells, in detail, highlighting the difference between cell wall and cell membrane.
Cell wall is the rigid, outermost layer of cells found in plant, fungi and most protists cells. The cell wall of plants is made up of cellulose, whereas that of bacteria is composed of peptidoglycan. The plant cell wall is synthesized by protoplast near the cell membrane. Cellulose layers are laid at angles, to enhance the strength of the cell wall. The main functions of cell wall include; providing structural strength, giving a definite shape to cell, and protecting the cell against pathogens and mechanical injury.
Cell membrane or plasma membrane is found in almost all the living cells. It encloses a cell and separates its content from the outer environment. The plasma membrane is made up of phospholipid bilayer with proteins embedded in it. It is flexible and about 5 to 10 nm thick.
The model of the cell membrane is called ‘fluid mosaic model’, a mosaic of proteins in or on the fluid lipid bilayer. Based on the association of membrane proteins with the membrane, there are two types of membrane proteins; (1) integral proteins, which are embedded in the membrane, and (2) peripheral proteins, which are found on the surface of the membrane. (Read the Difference Between Integral Proteins and Peripheral Proteins). These transmembrane proteins are able to serve as carriers; which carry molecules across the membrane by active or passive transport, channel proteins; which passively transport molecules across the membrane, and receptor proteins; which transmit information into the cell. (Read the Difference Between Carrier Proteins and Channel Proteins). In addition to proteins and phospholipids, there are carbohydrate chains associated with proteins (glycoproteins) and lipid bilayer (glycolipids). They are basically important in ‘self’ recognition and tissue recognition of cells. The main functions of the cell membrane include; providing a shape to cell, acting as a barrier, selective transportation of molecules across the membrane, and regulation of movements of ion in and out of the cell.
What is the difference between Cell Wall and Cell Membrane?
• Cell wall is present in plant, fungi and most protists cells, except animal cells. In contrast, cell membrane is present in all types of cells including animal cells.
• Cell wall is the outermost covering of the plant cells, whereas cell membrane is the outermost covering of the animal cells.
• Cell wall is present outside the plasma membrane. In contrast, cell membrane is present outside of the cytoplasm.
• Cell wall is a rigid and thick cell component, whereas cell membrane is flexible and comparatively thin.
• Cell membrane is selectively permeable, whereas cell wall is permeable.
• Cell membrane is composed of phospholipids and proteins while cell wall is made up of cellulose.