Structure of cell membrane

 Introduction

The cell membrane is also known as the plasm membrane. Plants differ from that of animal cells because only the plant cells have both the cell wall and cell membrane. Plasma membrane is found just beneath the cell wall containing 3 major components; lipid and protein bilayer and the cholesterol. The arrangement of membranous elements help to make the cell membrane semi-permeable and selective. Plant`s cell membrane is a semi-permeable membrane allowing only the necessary elements such as sunlight, fluids, nutrients and minerals. The cell membrane is a  thin spongy bed assist in providing an optimal medium to receive and excrete the necessary components. The difference in the electrical potential between inside and outside the plasma membrane helps in the fluid and mineral shift.

 

Structure of the cell membrane 

 The cell membrane is a porous and multi-layered as it is made up of the 2 major components; glycoproteins and lipids(phospholipids). Then 2 layers are so arranged that they carefully monitor the entry and exit of minerals, fluids and gases. A typical cell membrane contains up of 40% lipid, 60%  protein, and 1-10% carbohydrate. The arrangement of phospholipids makes the cell membrane look like a bi-layer allowing the material in and out through selective diffusion. Selective diffusion is the tendency of the cell membrane to chose only the necessary elements. The lipids found in the cell membrane are of 2  types, the phospholipids and sterols. Both of them readily dissolved in the organic solvents, and they are hydrophilic in nature(attracted towards the water). Hydrophilic heads found on the cell membrane assist in attracting the water when the fluid approaches the cell membrane. On the other hand, proteins found in the cell membrane are 2 types, I, e extrinsic and intrinsic. Extrinsic proteins are loosely attached by ionic bonds against the electrically charged phosphoryl surface of the bilayer. The intrinsic proteins are closely embedded within the phospholipid bilayer.

 

 

Phospholipid and protein layers

Phospholipid and protein bilayers create a gradient providing an accurate direction and channel for the movement of particles. The chemical structure of the cell membrane is made in such a way that they create a formidable barrier that can detect the difference between the necessary products and the toxic products. Bilayer allows only the soluble substances and solutes, but they resist tough material. But the lipid bilayer assist in repelling many large, dangerous water-soluble molecules. Cell membranes also assist in endocytosis; a process in which the foreign material is engulfed by the cell membrane by forming an invagination around it. The membranous vacuole found inside the plant cell will process the dead matter so that the cell is healthy and clean.  Protein layers are classified as surface proteins and integral proteins hence it is called bi-layer. Cholesterol is also vital for the performance of many cellular functions. Cholesterol has a polar head, a planar steroid ring, and a non-polar hydrocarbon tail ; 3 elements act together helping to maintain the cellular stability when there is a huge fluctuation in the cellular temperatures as a result of many metabolic processes. 

 

Related topics

1           

Structure and functions of cells

2

Structure of plant cell

3

Cell cycle and cell division

4

Tissues in our body

 

Questions

  1. What is the difference between cell wall and cell membrane?

  2. What are the major functions of cell membrane?

  3. Does all the organisms  have cell membrane give reason.

  4. Explain about the Phospholipid and protein layers.

  5. What is a semi-permeable membrane ? Explain.

 

 



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