Cell membrane is selectively permeable or semi-permeable
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Hint:Plasma membrane is also called cell membrane. The plasma membrane or the cell membrane surrounds the cell and encloses its contents of cytoplasm and nucleoplasm. It separates the cell from the outside environment.
Complete answer: Permeability can be defined as the degree of diffusion of liquids, gases, and other dissolved substances through a membrane. This ability of a substance to regulate passage through the membrane is called permeability. Depending upon the permeability of the membrane, it is classified as a freely permeable membrane, selectively permeable membrane, impermeable membrane, and a semi-permeable membrane. The selectively permeable membrane or differentially permeable membrane allows passage of only selected molecules to pass through it. Some of the examples of the selectively permeable membrane are the membrane that surrounds the subcellular organelles, tonoplast, and cell membrane. Cellophane is an example of a non-living selectively permeable membrane. The rate of permeability of different molecules differs in selectively permeable membranes. Plasma membrane which is also called cell membrane is selectively permeable as it only allows selected molecules of solute and solvent to pass through it. Show  So, option B is the correct option. Note: Freely permeable membrane allows passage of various molecules through the membrane. The cell wall is an example of a freely permeable membrane. The impermeable membrane does not allow any kind of movement through it. A Cutinized cell wall is an example of an impermeable membrane. A semi-permeable membrane allows passage of only solvent molecules to pass through it. The animal bladder, parchment membrane are examples of semi-permeable membranes. Apart from natural membranes, artificial membranes are also present that are semi-permeable in nature. Plasma membranes act not only as a barrier, but also as a gatekeeper. It must allow needed substances to enter and cell products to leave the cell, while preventing entrance of harmful material and exit of essential material. In other words, plasma membranes are selectively permeable—they allow some substances through but not others (Figure 1). If the membrane were to lose this selectivity, the cell would no longer be able to maintain homeostasis, or to sustain itself, and it would be destroyed. Some cells require larger amounts of specific substances than other cells; they must have a way of obtaining these materials from the extracellular fluids. This may happen passively, as certain materials move back and forth, or the cell may have special mechanisms that ensure transport. Most cells expend most of their energy, in the form of adenosine triphosphate (ATP), to create and maintain an uneven distribution of ions on the opposite sides of their membranes. The structure of the plasma membrane contributes to these functions. Plasma membranes are asymmetric, meaning that despite the mirror image formed by the phospholipids, the side of the membrane facing the inside of the cell is not identical to the exterior of the membrane. Proteins that act as channels or pumps work in one direction. Carbohydrates, attached to lipids or proteins, are also found on the exterior surface of the plasma membrane. These carbohydrate complexes help the cell bind substances in the extracellular fluid that the cell needs. This adds considerably to the selective nature of plasma membranes. Recall that plasma membranes have hydrophilic and hydrophobic regions. This characteristic helps the movement of certain materials through the membrane and hinders the movement of others. Lipid-soluble material can easily slip through the hydrophobic lipid core of the membrane. Substances such as the fat-soluble vitamins A, D, E, and K readily pass through the plasma membranes in the digestive tract and other tissues. Fat-soluble drugs also gain easy entry into cells and are readily transported into the body’s tissues and organs. Molecules of oxygen and carbon dioxide have no charge and pass through by simple diffusion. Polar substances, with the exception of water, present problems for the membrane. While some polar molecules connect easily with the outside of a cell, they cannot readily pass through the lipid core of the plasma membrane. Additionally, whereas small ions could easily slip through the spaces in the mosaic of the membrane, their charge prevents them from doing so. Ions such as sodium, potassium, calcium, and chloride must have a special means of penetrating plasma membranes. Simple sugars and amino acids also need help with transport across plasma membranes. Unless otherwise noted, images on this page are licensed under CC-BY 4.0 by OpenStax. Text adapted from: OpenStax, Concepts of Biology. OpenStax CNX. May 18, 2016 http://cnx.org/contents/[email protected] Is cell membrane selectively permeable or semipermeable?The cell membrane is semipermeable (or selectively permeable). It is made of a phospholipid bilayer, along with other various lipids, proteins, and carbohydrates.
Is cell membrane is called semi permeable membrane?The cell membrane is called selectively permeable as it only allows specific molecules to pass. Only specific molecules like water and gaseous molecules can pass through the cell membrane directly. It stops the flow of other molecules towards the two sides.
Are all cell membranes selectively permeable?All cells are surrounded by a selectively-permeable membrane. This membrane not only surrounds the cellular organelles but also acts as a barrier between the internal and the external environment.
Why is cell membrane semi permeable?The cell membrane is semi-permeable because the phospholipid bilayer prevents the diffusion of most molecules across the membrane due to the hydrophobic nature of the tails.
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