What is the term for a solution where the concentration of solutes is equal on both sides of a membrane?

A solution where the concentration of solutes is equal on both sides of a membrane is referred to as isotonic. In an isotonic solution, there is no net movement of water across the membrane, as the osmotic pressure is balanced on both sides. This means that the cells placed in an isotonic environment will neither swell nor shrink, maintaining their normal shape and function.

In contrast, a hypotonic solution has a lower concentration of solutes compared to the inside of a cell, leading to water entering the cell and potentially causing it to swell or burst. A hypertonic solution, on the other hand, has a higher concentration of solutes, resulting in water exiting the cell, which can cause it to shrivel. The term "concentrated" does not specifically refer to the balance of solute concentration across a membrane and is not a standard term used to describe osmotic conditions in biology.