Final answer:
The fluidity of the membrane facilitates the diffusion of molecules such as gases, the movement and function of membrane-bound proteins, and the active transport of molecules against their concentration gradient using energy.
Step-by-step explanation:
The fluidity of the membrane allows for a number of critical processes that are essential for the functioning of cells. For instance, it permits the diffusion of molecules across the membrane, such as the passive transport of gases like oxygen (O2) and carbon dioxide (CO2), which do not require energy to move across the membrane due to their nonpolar nature. Molecules diffuse from areas of high concentration to areas of low concentration, a process vital for cellular respiration and gas exchange in the lungs.
Furthermore, fluidity facilitates the movement of membrane-bound proteins, which are essential for various cell functions including transport, signal transduction, and cell-to-cell recognition. Proteins embedded in the membrane can move laterally to interact with other proteins or molecules, enabling processes such as facilitated diffusion and active transport. Facilitated diffusion uses specific protein channels to assist hydrophilic substances like glucose in moving down their concentration gradient without energy expenditure. Lastly, the fluidity of the membrane allows for active transport, where substances are moved against their concentration gradient with the aid of energy from ATP, which is indispensable for maintaining concentration gradients essential to cell function.