Which external factor can notably affect membrane function during experiments?

The concentration of the solvent plays a crucial role in membrane function, particularly in experiments dealing with diffusion, osmosis, and permeability. Changes in solvent concentration can influence the movement of water and solutes across the membrane, which is a fundamental aspect of many biological and chemical processes. For instance, in a hypertonic solution, water would move out of cells, potentially leading to cell shrinkage, while in a hypotonic solution, water would enter cells, possibly resulting in swelling and even lysis. This dynamic directly affects how the membrane behaves during experiments, making solvent concentration a significant external factor to consider.

The other factors, while they may have their own effects in different contexts, do not specifically impact membrane function to the same degree. The type of membrane used determines baseline characteristics but does not address variations in the solvent environment. Ambient light conditions can affect certain photochemical reactions but do not typically influence membrane permeability or function in a direct manner. Similarly, the size of the experimental setup might create logistical challenges or affect heat distribution but is not inherently related to the functional dynamics of the membrane itself.