Which of the following are the components of a plasma membrane?

With few exceptions, cellular membranes — including plasma membranes and internal membranes — are made of glycerophospholipids, molecules composed of glycerol, a phosphate group, and two fatty acid chains. Glycerol is a three-carbon molecule that functions as the backbone of these membrane lipids. Within an individual glycerophospholipid, fatty acids are attached to the first and second carbons, and the phosphate group is attached to the third carbon of the glycerol backbone. Variable head groups are attached to the phosphate. Space-filling models of these molecules reveal their cylindrical shape, a geometry that allows glycerophospholipids to align side-by-side to form broad sheets (Figure 1).

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What are 5 components of the cell plasma membrane?
What are the four main components of plasma membrane?
What are the components of the plasma membrane quizlet?
Which of the following is not component of a plasma membrane?

Figure 1: The lipid bilayer and the structure and composition of a glycerophospholipid molecule

(A) The plasma membrane of a cell is a bilayer of glycerophospholipid molecules. (B) A single glycerophospholipid molecule is composed of two major regions: a hydrophilic head (green) and hydrophobic tails (purple). (C) The subregions of a glycerophospholipid molecule; phosphatidylcholine is shown as an example. The hydrophilic head is composed of a choline structure (blue) and a phosphate (orange). This head is connected to a glycerol (green) with two hydrophobic tails (purple) called fatty acids. (D) This view shows the specific atoms within the various subregions of the phosphatidylcholine molecule. Note that a double bond between two of the carbon atoms in one of the hydrocarbon (fatty acid) tails causes a slight kink on this molecule, so it appears bent.

Glycerophospholipids are by far the most abundant lipids in cell membranes. Like all lipids, they are insoluble in water, but their unique geometry causes them to aggregate into bilayers without any energy input. This is because they are two-faced molecules, with hydrophilic (water-loving) phosphate heads and hydrophobic (water-fearing) hydrocarbon tails of fatty acids. In water, these molecules spontaneously align — with their heads facing outward and their tails lining up in the bilayer's interior. Thus, the hydrophilic heads of the glycerophospholipids in a cell's plasma membrane face both the water-based cytoplasm and the exterior of the cell.

Altogether, lipids account for about half the mass of cell membranes. Cholesterol molecules, although less abundant than glycerophospholipids, account for about 20 percent of the lipids in animal cell plasma membranes. However, cholesterol is not present in bacterial membranes or mitochondrial membranes. Also, cholesterol helps regulate the stiffness of membranes, while other less prominent lipids play roles in cell signaling and cell recognition.

Figure 2: The glycerophospholipid bilayer with embedded transmembrane proteins

In addition to lipids, membranes are loaded with proteins. In fact, proteins account for roughly half the mass of most cellular membranes. Many of these proteins are embedded into the membrane and stick out on both sides; these are called transmembrane proteins. The portions of these proteins that are nested amid the hydrocarbon tails have hydrophobic surface characteristics, and the parts that stick out are hydrophilic (Figure 2).

At physiological temperatures, cell membranes are fluid; at cooler temperatures, they become gel-like. Scientists who model membrane structure and dynamics describe the membrane as a fluid mosaic in which transmembrane proteins can move laterally in the lipid bilayer. Therefore, the collection of lipids and proteins that make up a cellular membrane relies on natural biophysical properties to form and function. In living cells, however, many proteins are not free to move. They are often anchored in place within the membrane by tethers to proteins outside the cell, cytoskeletal elements inside the cell, or both.

Hint:Plasma membrane is also called the cell membrane. It is the membrane found in all the cells. It separates the interior of the cell from the external environment of the cell. Plasma membrane is semi-permeable membrane which means that it allows the movement of selective molecules or ions across itself.

Complete answer :
>Cilia:-Cilia are short hair like structures.They are used to move the entire cell or help in the movement of substances along the outer surface of the cell.Cilia are present in many numbers.They extend along the entire surface of the plasma membrane.
>Microvilli:-Microvilli are the microscopic protrusion of the plasma membrane.Microvilli increase the surface area of the cell for diffusion and minimize any increase in volume of the cell.They are involved in absorption, secretion, cellular adhesion and mechanotransduction.Microvilli because of its vital function is packed with enzymes that help in the breakdown of the complex nutrients into the simpler compounds so that they can be easily absorbed.So the microvilli also increases the number of digestive enzymes that are present on the surface of the cell.
>Desmosome:-A desmosome is a cell structure which is specialized for cell to cell adhesion.Desmosomes are one of the stronger cell-to-cell adhesion type.Desmosomes maintain the mechanical integrity of the tissue.They are found in tissues which experience more mechanical stress such as cardiac muscle tissue, bladder tissue, etc.The term desmosome was coined by Josef Schaffer in 1920.Desmosomes are also called as the adherens junctions (AJs).
>Gap Junctions:-Gap junctions are the specialized intercellular connections between the animal cells.They directly connect the cytoplasm of two cells.Gap junctions allow various molecules, ions and electrical impulses to directly pass through a regulated gate between cells.Gap junction is also called nexus or macula communicans.They are analogous to plasmodesmata that are present in the plant cells.
Therefore, it has been clear from the above discussion that Microvilli components of the plasma membrane are involved in the enlargement of cell surface area.

Hence, option B is the correct answer.

Note:Plasma membrane is also called as the cell membrane. It is the membrane found in all the cells. It separates the interior of the cell from the external environment of the cell. Plasma membrane is semi-permeable membrane which means that it allows the movement of selective molecules or ions across itself.

What are 5 components of the cell plasma membrane?

The principal components of a plasma membrane are lipids (phospholipids and cholesterol), proteins, and carbohydrates attached to some of the lipids and some of the proteins. A phospholipid is a molecule consisting of glycerol, two fatty acids, and a phosphate-linked head group.