Questions: A concentration this affects the movement of molecules across membranes is observed when the two sides of a membrane contain different concentrations of a particular molecule (e.g. glucose).

The answer is: gradient

Explanation:

• The term "concentration gradient" refers to the difference in the concentration of a substance between two areas. In the context of the question, it describes the situation where there are different concentrations of a molecule, such as glucose, on either side of a membrane.
• This concentration gradient is crucial because it drives the movement of molecules across the membrane, typically from an area of higher concentration to an area of lower concentration, a process known as diffusion.
• The movement of molecules across membranes due to concentration gradients is a fundamental concept in biology and chemistry, particularly in the study of cellular processes and membrane transport mechanisms.