What means that the transport protein makes it easier for a molecule that cannot directly cross the cell membrane to enter or exit a cell?

Answer 1

When a transport protein facilitates the movement of a molecule across the cell membrane, it acts as a channel or carrier that helps the molecule bypass the lipid bilayer, which is generally impermeable to large or polar substances. This process, known as facilitated diffusion, allows essential molecules, like glucose or ions, to enter or exit the cell efficiently without expending energy. By providing a pathway, transport proteins ensure that cells can maintain homeostasis and properly regulate their internal environment.