The key difference between semipermeable and selectively permeable membrane is that semipermeable membrane allows some particles to pass through, depending on the size of the particles, whereas selectively permeable membrane chooses what particles pass through independent of the size of the particles.
Semipermeable membranes and selectively permeable membranes are two types of membranes that allow some particles to pass through the membrane according to some factors.
CONTENTS
1. Overview and Key Difference
2. What is a Semipermeable Membrane
3. What is a Selectively Permeable Membrane
4. Semipermeable vs Selectively Permeable Membrane in Tabular Form
5. Summary – Semipermeable vs Selectively Permeable Membrane
What is a Semipermeable Membrane?
A semipermeable membrane is a kind of biological or synthetic polymeric membrane that allows certain molecules or ions to pass through the membrane via osmosis. The rate of this movement depends on certain parameters such as the pressure, concentration, temperature of the molecules or solutes, and the permeability of the membrane to each solute. Moreover, based on the membrane and solutes, permeability depends on the solute size, solubility, chemistry, etc. There are many natural and synthetic materials that can be both thick and semipermeable. For example, a thin film on the inside of the egg.
Generally, biological membranes are selectively permeable, and there is a passage for molecules that are controlled by facilitated diffusion, passive transport, and active transport that is regulated by proteins embedded in the membrane. E.g. lipid bilayer of the cell. Here, phospholipids are arranged into a double layer, and it is very specific and shows permeability. Moreover, the information can pass through the plasma membrane when signaling molecules are bound to receptors in the cell membrane. Here, the signaling molecules bind to the receptors, altering the structure of proteins. A change in the protein structure can also initiate a signaling cascade.
Some other examples of semipermeable membranes include cation exchange membranes, anion exchange membranes, alkali anion exchange membranes, and proton exchange membranes.
What is a Selectively Permeable Membrane?
Selectively permeable membranes are a type of membrane that can regulate the movement of substances in and out of the cell. A plasma membrane is a good example of a selectively permeable membrane. A plasma membrane tends to allow some material to pass through it while blocking other materials from entering it.
Selective permeability can be described as a property of cellular membranes that allows only certain molecules to enter or exit the cell. This is important in maintaining the internal order of the cell irrespective of the changes to the environment.
What is the Difference Between Semipermeable and Selectively Permeable Membrane?
We can categorize membranes into two groups as semipermeable membranes and selectively permeable membranes, according to the nature of the movement of particles through these membranes. The key difference between semipermeable and selectively permeable membrane is that semipermeable membrane allows some particles to pass through depending on the size of the particles, whereas selectively permeable membrane chooses what particles pass through independent of the size of the particles. Further, some examples of semipermeable membranes include frog skin. Synthetic membranes such as cellophane, membranes made with polyvinyl alcohol, polyurethane, etc., while the phospholipid bilayer of the cell membrane is an example of a selectively permeable membrane.
Below is a summary of the difference between semipermeable and selectively permeable membrane in tabular form for side-by-side comparison.
Summary – Semipermeable vs Selectively Permeable Membrane
Semipermeable membranes are a kind of biological or synthetic polymeric membrane that allows certain molecules or ions to pass through the membrane via osmosis, while selectively permeable membranes are a kind of membrane that can regulate the movement of substances in and out of the cell. The key difference between semipermeable and selectively permeable membrane is that semipermeable membrane allows some particles to pass through depending on the size of the particles, whereas selectively permeable membrane chooses what particles pass through independent of the size of the particles.
Reference:
1. “Semipermeable membrane.” Wikipedia. Wikipedia Foundation.
Image Courtesy:
1. “Semipermeable membrane (SVG)” By Freemesm – Own work (CC BY-SA 3.0) via Commons Wikimedia