Although the plasma membrane (or cell membrane) had already set the boundaries for the inside and outside cellular environment, many cells are still encircled by a wide array of insoluble components.
We will explore the functions, structures and types of cell wall.
Table of Contents
- What is the cell wall?
- Bacterial Cell Wall
- Functions of Bacterial Cell Wall
- Plant Cell and Fungal Cell Wall
- Functions of Plant Cell and Fungal Wall
What is the cell wall?
Bacterial Cell Wall
Bacterial cell walls are responsible for the maintenance of the cell shape and the prevention of cell lysis (cell bursting due to high osmotic pressure). The Gram staining procedure developed is based upon the ability of bacteria to take in and keep the crystal violet stain (those that will retain it are considered to be Gram positive and Gram negative if otherwise).
1. Gram Negative Bacteria
- An example of a Gram negative bacterium is the Escherichia coli (or E. coli).
2. Gram Positive Bacteria
- Examples of Gram positive bacteria are the common pathogens Staphylococcus aureus and Streptococcus (both responsible for respiratory infections), Corynebacterium diphteriae (responsible for diphteria), and Bacillus anthracis (responsible for anthrax).
Even with such differences in structure, the main constituent of cell walls of bacteria is the macromoleculepeptidoglycan . This macromolecule is composed of linear chains of polysaccharides linked by peptides, and as a structure, serves as the foundation of cell wall that defines the shape of bacteria and attaches protein complexes to the surface of the cells. Interestingly though, peptidoglycan makes bacteria vulnerable targets for antibiotics.
Functions of Bacterial Cell Wall
While the structural components of the cell wall differs in Gram negative and Gram positive bacteria, the functions of the cell wall is universal for all bacteria possessing this structure. The following are some of the major functions of the cell wall in bacteria:
2. Maintenance of Cell Shape
3. Facilitate in Cell-To-Cell Communication
Plant Cell and Fungal Cell Wall
Unlike those of the prokaryotes, the components of eukaryotic (higher plants, algae, and fungi) cell walls are mainly polysaccharides. The basic structural component of the cell walls of higher plants and most algae is cellulose. Cellulose is a polymer of glucose residues that are connected via β(1→4) linkages.
The cell walls of fungi, on the other hand are made up of the polymer chitin. Chitin is a polymer of N-acetylglucosamine residues that are also connected via β(1→4) linkages. Chitin is also the structural component of arthropod exoskeleton.
Functions of Plant Cell and Fungal Wall
It is important to note that while plant cells and fungal cells are composed of different material; both are still made up of carbohydrate polymers. Hence, they possess almost the same attributes and functions as well.
The following are some of them:
1. Structural Support
2. Resist Turgor Pressure
3. Control Growth and Diffusion
Although much has already been known about the biosynthesis of cell walls, there still remain large mysteries about its three-dimensional structure and organization, physiological activities, and nature during cell division and growth.
So now, after knowing the tremendous importance of the cell wall to living organisms (i.e. bacteria, plants, and fungi), why do you think has evolution allowed animal cells to develop without it?
-  – “Medical Definition of Gram-positive”. Accessed May 21, 2017. Link.
-  – “Peptidoglycan.” Encyclopedia of Life Sciences. Accessed May 21, 2017. Link.
-  – “Bacterial Cell Walls: Structure, Function & Types – Video & Lesson Transcript | Study.com”. Accessed May 21, 2017. Link.
-  – “Cell Walls and the Extracellular Matrix – The Cell – NCBI Bookshelf”. Accessed May 21, 2017. Link.
-  – “Structure of Cellulose Microfibrils in Primary Cell Walls from Collenchyma”. Accessed May 21, 2017. Link.
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