Explain what is meant by the terms isotonic and isosmotic. Is every isosmotic so

Question

Explain what is meant by the terms isotonic and isosmotic. Is every isosmotic solution isotonic? Explain and provide an example Is every isotonic solution isosmotic? Explain and provide an example Many membrane proteins contain transmembrane segments (ie segments which penetrate through the membrane). How must these proteins be formed to allow them to act as an ionic channel? What specialisation would you need to allow it to function as a voltage-gated channel? If sodium is a smaller ion than potassium, then how can a channel be specific for potassium (ie. does not also allow sodium through)?

Explanation / Answer

An isotonic solution refers to two solutions having the same osmotic pressure across a semipermeable membrane while an isosmotic solution is when two solutions have the same number of solutes.

A single solution at equilibrium is always isotonic and isosmotic with itself. However, if you have two different solutions, one on each side of a semi-permeable membrane, each of which has the same osmotic pressure but a different solute, then you can can have a solution that is isosmotic but not isotonic.

Isosmotic solution is not always isotonic solution: A isosmotic solution can not be isotonic.

Isotonic solutions contain only non-penetrating solutes and have the same osmotic pressure as the cells they surround. They are neither absorbed nor they absorb anything from the surrounding cell. The isosmotic solution contains both penetrating and non-penetrating solutes. They have the same osmotic pressure of the surrounding cells. Penetrating solutes are solutes that can pass through the membrane of the cell and increases the osmotic pressure in the cell. This forces the cell to absorb more water to equalize the difference in pressure. This may lead to bursting of the cell when too much water is absorbed.

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