Structure Of Cell Membrane And Its Function – The structure and functions of the cell membrane discussed in this article are intended to provide basic information about this cell organelle. Read on to find out more.

The cell membrane is a protective covering that acts as a barrier between the internal and external environments of a cell (in animals). In plant cells, the membrane surrounds the protoplasm. This organelle is also called the plasma membrane. Images taken by electron microscopy show the double-layer structure of cell membranes. The characteristic feature of this organelle is that it only allows certain substances to pass through. Most research studying cell membrane structure uses red blood cells (RBCs) because the lack of internal membranes and nuclei in red blood cells makes the isolation process quite easy to perform.

Structure Of Cell Membrane And Its Function

The following sections present information about the function of the cell membrane and its structure. This description of cell membrane structure and functions is intended to help better understand how it works.

Cell Membrane — Structure & Function

The cell membrane consists of two layers made up of phospholipids. The bilayer is formed by the arrangement of phospholipids such that their head regions (which are hydrophilic) face both the external environment and the internal cytosolic environment. The (hydrophobic) tails of these phospholipids face each other. The forces underlying the formation of this double layer are electrostatic, van der Waals interactions, noncovalent interactions, and hydrogen bonds. This special arrangement of hydrophilic and hydrophobic layers prevents nucleic acids, amino acids, proteins, carbohydrates and ions from passing through the bilayer. The following are the different parts of the cell membrane.

Demarcating the boundaries of a cell is the main function of the plasma membrane. The contents of a cell are carried by this membrane. The cell membrane not only supports the matter present in the cells, but also the function of maintaining contact with other cells. The plant cell membranes enjoy additional protection in the form of cell walls; However, in animals, the cell membrane is the only covering/encapsulation. Proteins that make up the membrane (or become embedded in it) carry out the diffusion of elements in a selective manner.

The plasma membrane is an important part of a cell as it offers it protection and also helps maintain the correct shape. The structure and function of the cell membrane presented in the article should help to learn more about this organelle.

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Cell Structure And Function

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Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent before running these cookies on your website. The cell membrane (also known as the plasma membrane or cytoplasmic membrane and formerly called the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the external environment (the extracellular space).

Function Of Cell Membrane (a Level Biology)

The cell membrane consists of a lipid bilayer, which consists of two phospholipid layers with cholesterols (a lipid component) sandwiched between them and maintains adequate membrane fluidity at different temperatures. The membrane also contains membrane proteins, including integral proteins that span the membrane and serve as membrane transporters, as well as peripheral proteins that attach loosely to the outer (peripheral) side of the cell membrane and act as enzymes to facilitate interaction with the cell environment.

Glycolipids, which are embedded in the outer lipid layer, serve a similar purpose. The cell membrane controls the movement of substances in and out of a cell and is selectively permeable to ions and organic molecules.

In addition, cell membranes are involved in a variety of cellular processes such as cell adhesion, ionic conductance, and cell signaling, and serve as an attachment surface for several extracellular structures, including the cell wall and the carbohydrate layer called the glycocalyx, the intracellular network of protein fibers, the cytoskeleton. In synthetic biology, cell membranes can be artificially reassembled.

While Robert Hooke’s discovery of cells in 1665 led to the proposal of the cell theory, Hooke misled the cell membrane theory that all cells contained a hard cell wall, as only plant cells could be observed at that time.

Plant Cell: Parts • Microbe Online

Microscopists focused on the cell wall for well over 150 years until advances in microscopy were made. In the early 19th century, it was recognized that cells were separate, unconnected units connected by single cell walls after it was discovered that plant cells could be separated. This theory was extended to animal cells to propose a universal mechanism for cell protection and development. In the second half of the 19th century, microscopy was not yet advanced enough to distinguish between cell membranes and cell walls. However, some microscopists at this time correctly noted that although they were invisible, it could be concluded that cell membranes in animal cells existed due to the intracellular movement of components on the inside but not on the outside, and that membranes were not the equivalent of a plant one be cell wall. It was also concluded that cell membranes were not vital components for all cells. Many people refuted the existence of a cell membrane as early as the 19th century. In 1890, an update of cell theory stated that cell membranes existed but were merely secondary structures. It was only later studies of osmosis and permeability that cell membranes gained greater recognition.

Speculations about the description of the cell membrane bilayer structure arose on the basis of crystallographic studies and soap bubble observations. To accept or reject the hypothesis, the researchers measured the membrane thickness. These researchers extracted the lipid from human red blood cells and measured the amount of surface area the lipid would cover as it spread across the surface of the water. Because mature mammalian red blood cells lack both nuclei and cytoplasmic organelles, the plasma membrane is the only lipid-containing structure in the cell. Consequently, it can be assumed that all lipids extracted from the cells were in the plasma membranes of the cells. The ratio of the water surface covered by the extracted lipid to the calculated surface area of ​​the red blood cells from which the lipid was derived was 2:1 (approximately) and they concluded that the plasma membrane contains a lipid bilayer.

In 1925, Fricke found that the thickness of erythrocyte and yeast cell membranes was between 3.3 and 4 nm, a thickness consistent with a lipid monolayer. The choice of dielectric constant used in these studies has been questioned, but future tests failed to refute the results of the first experiment. Separately, the leptoscope was invented to measure very thin membranes by comparing the intensity of light reflected from a sample with the intensity of a membrane standard of known thickness. The instrument was able to resolve thicknesses that depended on pH measurements and the presence of membrane proteins, ranging from 8.6 to 23.2 nm, with the lower measurements supporting the lipid bilayer hypothesis. Later in the 1930s, the membrane structure model broadly evolved into the paucimolecular model of Davson and Danielli (1935). This model was based on studies of the surface tension between oils and echinoderm eggs. Because surface tension values ​​appeared to be much lower than would be expected for an oil-water interface, it was hypothesized that a substance was responsible for reducing interfacial tensions at the cell surface. It was suggested that there was a lipid bilayer between two thin layers of proteins. The paucimolecular model gained immediate popularity and dominated cell membrane studies for the next 30 years until it was rivaled by the fluid mosaic model of Singer and Nicolson (1972).

Despite the numerous models of the cell membrane that were proposed before the fluid mosaic model, it remains the primary archetype for the cell membrane long after its introduction in the 1970s.

Cell Membrane: Video, Anatomy, Definition & Function

Although the fluid mosaic model has been modernized to detail contemporary discoveries, the fundamentals have remained the same: the membrane is a lipid bilayer composed of hydrophilic outer heads and a hydrophobic interior in which proteins can interact with hydrophilic heads through polar interactions

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