This membrane is known by various names – cell membrane, plasma membrane or plasmalemma simply. In some strains of bacteria and plants, the plasma membrane attached to the rigid cell wall, which is protective function. While in the case of animal cells, the cell wall absent and protoplasm is described by the plasma membrane.
Each type of living cell, either prokaryotic or eukaryotic simple top, has a membrane between the cell components of the environment. This membrane is known by various names – cell membrane, plasma membrane or plasmalemma simply. In some strains of bacteria and plants, the plasma membrane attached to the rigid cell wall, which is protective function. While in the case of animal cells, the cell wall absent and protoplasm is described by the plasma membrane. Learn more about the plant cell from animal cells.
Plasma membrane is the main function of regulating the transport of substances in the cell to outside and vice versa. The special structure of the plasma membrane plays a crucial role in the overall function of the cell. Simply put, it works like the skin of animals. Several scientific hypotheses have been proposed to explain the structure of the plasma membrane, including the widely accepted theory is the fluid mosaic model. To learn more about the different parts of a cell.
The structure of the plasma membrane: fluid mosaic model
The fluid mosaic model has been developed by SJ Singer and Garth Nicolson in 1972. According to this theory, the plasma membrane consists of carbohydrates and different types of fats and proteins. And the model is named after the structure of the plasma membrane, the membrane is not rigid, but rather a type of liquid, which contains several molecules as a mosaic. These molecules are arranged in an appropriate way, which helps in the selective movement of substances. He looks below a small example of the fluid mosaic model:
lipid bilayers: The core structure of the plasma membrane is lipid bilayers. Types of lipids in the plasma membrane are phospholipids, cholesterol and glycolipids. But, since most molecules are the type of phospholipid (containing a phosphate group), the two layers of lipids called phospholipids layers.
The lipid tails are water-repellent (hydrophobic), while the heads of the phosphate is taken from the water (hydrophilic). The double layers of phospholipids arranged in a certain way, with the hydrophobic tails face inward (toward each other) and adjusting the hydrophilic heads outward. Therefore, two sides of the plasma membrane to the cytosol and the other against the external environment, is hydrophilic in nature.
Membrane proteins: another key part of the plasma membrane are proteins that help in the selective transport of macromolecules such as sucrose, amino acids and ions. Based on the localization of proteins with regard to phospholipid bilayers, two types of proteins:
* The integral membrane protein binds to lipid bilayers structure. And integral proteins that span the phospholipid bilayers are called transmembrane proteins.
* Peripheral membrane proteins or indirectly linked closely to the membrane. They are not covalently linked to lipids or proteins intrinsic ends.
Carbohydrates: In addition to phospholipids and proteins in the cell membrane is also composed of carbohydrates, glycoproteins and glycolipids, mainly. These molecules are arranged exclusively in the outer membrane of the cells, how many carbohydrates are exposed on the outer surface of the cell.
Speaking about the role of the plasma membrane is the most important functions in the cell recognition and regulation of cellular transport. Small molecules such as oxygen, nitrogen, etc. are allowed to freely enter or exit the cell (passive transport), while large molecules such as amino acids selectively passed through the membrane against the concentration gradient (active transport). For example, through active transport of waste is expelled, while other useful substances into the cell. Learn more about the function of the cell membrane.
With this information on the structure and function of the plasma membrane, I hope you have clarified your doubts about the scheme of membrane molecules and their functions.