What is the term for a mechanical operation that involves the movement of substances across a membrane due to increased pressure?

The term that describes the mechanical operation involving the movement of substances across a membrane due to increased pressure is filtration. This process typically occurs in kidneys, where blood is filtered to remove waste products and excess substances, allowing smaller molecules and water to pass through while retaining larger molecules and cells.

In filtration, the driving force is hydrostatic pressure, which pushes fluids through a semi-permeable membrane, separating components based on size or solubility. This is distinct from diffusion and osmosis, which are driven by the concentration gradient instead of pressure. Absorption, on the other hand, generally refers to the process by which substances are taken up by cells and tissues, rather than movement across a membrane due to pressure.

Therefore, filtration accurately describes the specific mechanism of pressure-assisted movement across a membrane.