Semipermeable Membrane

Definition - What does Semipermeable Membrane mean?

A semipermeable membrane is a barrier that will only allow some molecules to pass through while blocking the passage of other molecules. A semipermeable barrier essentially acts as a filter. Different types of semipermeable membranes can block out different sized molecules. A semipermeable membrane can be made out of biological or synthetic material.

A semipermeable membrane may also be known as a partially permeable membrane or a deferentially permeable membrane.

Corrosionpedia explains Semipermeable Membrane

A semipermeable membrane allows some molecules to pass through it depending on the attributes of the molecules such as size or quantity. The process that occurs when a semipermeable membrane allows molecules to pass through is called diffusion. Diffusion usually occurs when molecules in a high concentration move to the other side of the membrane where there is a low concentration of those molecules.

There are many different types of semipermeable membranes, both organic and inorganic. A biological example of a semipermeable membrane is kidney tissue. Kidneys allow for some molecules to pass through them while blocking others such as human waste products. Synthetic versions of a semipermeable membrane are those used for water filtration or desalination. Synthetic semipermeable membranes are typically polymers, but they can be made out of other materials.

Semipermeable membrane is a term that is commonly, albeit mistakenly, interchanged with selectively permeable membrane. There are several key differences between the two that are important to note. One such difference is the fact that a selectively permeable membrane will allow for the passage of many different types of solutes.

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