semi-permeable membrane

A semi-permeable membrane is a barrier that allows certain substances to pass through while blocking others. Think of it like a filter: small molecules like water can easily move through, but larger particles, such as sugar or salt, cannot. This selective permeability is crucial in biological systems, like cell membranes, where it helps maintain the right balance of nutrients and waste. It also plays a vital role in processes like osmosis, where water moves across the membrane to equalize concentrations on both sides.