Most substances are able to undergo passive diffusion across the plasma membrane in order to enter a cell. True or False True False

False! While many substances can indeed cross the plasma membrane via passive diffusion, not all of them can. Factors such as size, polarity, and charge play crucial roles in determining whether a substance can diffuse through the lipid bilayer. Small nonpolar molecules like oxygen and carbon dioxide slip through easily, while larger or polar molecules often need help from transport proteins. Interestingly, cells have adapted to their environments with various mechanisms to regulate what enters and exits. For example, channels and carriers can facilitate the movement of specific molecules, ensuring that essential nutrients come in while keeping waste and harmful substances out. This selective permeability is vital for maintaining homeostasis in living organisms!