In this article, the plasma membrane structure of plants will be described in details.
The plasma membrane structure of plant, commonly known as the cell membrane or plasmalemma, is the major constituent of the cell that covers the cell organelles in cooperation with the cell wall. The plasma membrane in plants is built to separate the cell components from the changing external environment while simultaneously protecting them by acting as a covering coat.
The exterior environment is becoming increasingly chaotic as the temperature rises. Thus the cell membrane is essential for both protecting the cell from the outside world and keeping the cell organelles in place. As a result, the cell region’s entropy is protected from the external environment. It facilitates the formation of a closed system while also maintaining the cell’s shape.
The cytoplasm of plant cell:
Plant cell membranes are semi-permeable, meaning they selectively allow certain molecules to pass through while preventing the others. So, ultimately, it acts as a shield between the cell’s inside components and the surrounding environment.
The biological membrane or the plasma membrane composition varies depending on the cell type. The plasma membrane serves as an inner layer that can store cytoplasm, a gel-like substance.
Plasma membranes are defined in energy transduction, which is the action of transforming one form of energy into another. Solar energy is gathered by membrane-bound pigments throughout photosynthesis and processed into chemical energy stored in carbohydrate molecules.
The lipid bilayers of the plasma membrane
The plasma membrane comprises lipid bilayers, which are two molecules of tough outer coverings. Lipids and proteins are the macromolecules that are combined to form these bilayers. The plasma membranes are composed of bilayers, also known as the fluid mosaic model. In a fluid mosaic model, the lipids are composed of fluid, and on top of which, the proteins are embedded as a dynamic structure.
The temperature has a significant impact on membrane fluidity or membrane permeability. Plants frequently carry the burden of retaining membrane fluidity in low-temperature environments since they cannot adjust their internal temperature.
It reduces the fluidity of the membrane.
Although some carbohydrates are present in the bilayers, they are composed predominantly of these two macromolecule components. Lipids are insoluble in water or hydrophobic in nature and are the building blocks of the cell membrane. It functions as a signaling molecule and a power storage molecule.
In addition, cell membranes include a variety of lipids, the most common of which are phospholipids. The phospholipids in the cell membrane are fats and water-soluble molecules. It is essential for the transportation of materials and the maintenance of plant structures. The lipid content of plastid membranes is almost exclusively made up of glycosyl glycerides instead of phospholipids.
One head and two tails make up the phospholipids. The head of phospholipids is a single phospholipid molecule, a phosphate group on one terminal and two side-by-side strings of fatty acids that form the lipid tails. Also, the phospholipids have hydrophilic heads and hydrophobic tails. The head and tails of phospholipids are concluded in a hydrophobic environment.
Furthermore, phospholipids with short tails may constitute a micelle, which is a single-layered globe. They may also produce a liposome, a porous droplet of the bilayer or two-layer membrane if they have thicker tails.
Concerning phospholipids, the cell membrane also contains ‘sphingolipids,’ which are lipids similar to phospholipids. Sphingolipids are a form of lipid that has a sphingoid core base. Sphingolipids play a role in plant tissue regeneration, cell adhesion, and cell recognition and act as toxin receptors.
There are some proteins incorporated in the cell membrane and the lipid content. A cell membrane’s permanent component is proteins. It can alternatively permeate the cell membrane as a transmembrane and sometimes attach to one or both sides of the membrane as a monotopic constituent.
Three proteins are interconnected with the lipid bilayer: integral, peripheral, and anchored.
1)The integral protein:
The integral proteins are enclosed in lipids. Integral proteins deal with the outer environment from the interior of the cell. It is the hydrophobic substance of the membranes.
2)The peripheral protein:
Non-covalent bonds bind peripheral proteins to the surface of the membrane. Peripheral proteins disrupt the ionic and hydrogen interactions.
3)The anchored protein:
The anchored proteins are covalently bonded to lipid molecules that bind them to the surface of the membrane.
The carbohydrate content in the cell membrane is considerably less than the content of lipids and proteins in the plasma membrane. In actuality, carbohydrates are present on the cell membrane’s outer surface and are attached to either lipids or proteins to produce glycolipids or glycoproteins, respectively.
These carbohydrate networks can be linear or irregular. It can comprise up to 60 monosaccharide units. Together with protein molecules present in the cell membrane, such carbohydrates form different cellular identifiers that enable cells to identify one another.
Other cell components in plant cell
The plant cell wall:
The cell wall is the cell’s outermost coating, along with the cell membrane. Pectin, polysaccharide cellulose, and hemicellulose are all found in this stiff layer. Suberin, lignin, and cutin are some of the polymeric materials found in them. Some of it is made up of glycoproteins. Microtubules influence the development of the cell wall. It comprises three main layers: primary, secondary, and middle lamellas.
The cell wall protects the cell’s internal components while also providing structural strength. It serves as a strainer, filtering the substances that flow through it in the mode of diffusion. It also assisted in shielding the cell parts from mechanical damage.
The nucleus of a plant cell:
The nucleus of a plant cell carries the cell’s DNA or genetic information and shelters membrane-bound organelles. A nucleus is not observed in every plant cell. It has significant exposure to transcriptional regulators, which assist the cell in translating DNA and producing protein. It controls the immune system’s response to invaders.
The plastid of a plant cell:
Plastids are double-membrane organelles that are essential for the plant cell. It has its own DNA in it. Chloroplasts, Leucoplasts, and Chromoplasts, are the three basic types depending on their functionality. All of these types are required to conserve starch and the major active mechanism of photosynthesis.
Plant cells have leucoplast in their non-photosynthetic tissues or colorless plastids. They are designed to collect lipids, proteins, and carbohydrates in the form of starch. It can be seen in the plant’s roots, bulbs, and other parts.
Since chlorophyll is present in the plant cell leaflet, the chloroplast is a photosynthetic pigment. The chlorophyll gathers solar energy and employs to convert water and carbon dioxide into glucose. It is a phospholipid membrane-enclosed extended organ system.
In photosynthetic plants, chromoplasts are heterogeneous and contain colored plastids that are orange, red, and yellow pigments. These are essential for pigment synthesis and accumulation. It improves the coloring of all mature fruits and flowers.
Central Vacuole of a plant cell:
The plant has a large number of central vacuoles. The core vacuole is encircled by a membrane called tonoplast. Besides retention, the central vacuole is responsible for maintaining turgidity against the cell wall. A central vacuole is a type of bubble within a cell that is filled with water and macromolecules.
Lysosome of a plant cell:
Fatal sacks are lysosomes, which contain digestive juices in a contained membrane. Lysosomes undertake the task of cellular open dumping of unwanted waste materials. The central vacuoles in plants perform the function of lysosomes.
Mitochondria of a plant cell:
Mitochondria is the powerhouse or control center of the cell, storing energy for the plant’s activities. It’s located in the cytoplasm of the plant cell. They generate energy by dissolving sugar and carbohydrate molecules. It regulates the cellular metabolism of the plant cell.
Ribosome of a plant cell:
Ribosomes are the minutest membrane-bound compartments containing RNA and a small amount of protein. It is considered the protein manufacturer of the plant cell because it serves as a position for protein synthesis. It analyzes the messenger RNA or mRNA series and converts the genetic information into a chain of amino acids.
Golgi Apparatus of a plant cell:
The Golgi Complex is another name for the Golgi Apparatus. It’s in charge of transferring proteins to different regions of the plant. It also contributes to the modification and packing of lipids and proteins into compartments for transportation to specific targets.
The plasma membrane of plants is the fluid, rigid structure between the cell wall and the cytoplasm. The plasma membrane is a lipid bilayer primarily composed of lipids and proteins in plants, with a few carbohydrate molecules. Many biological functions in plants are carried out by it.