Final answer:
Drugs can cross cell membranes by passive transport, active transport, or vesicle transport. Passive transport relies on diffusion and does not require energy, while active transport requires energy to move drugs against a concentration gradient. Vesicle transport involves enclosing drugs in membrane vesicles.
Step-by-step explanation:
Drugs can cross cell membranes through various transport mechanisms. Three ways that drugs cross cell membranes include:
- Passive Transport: This method involves drugs moving across the cell membrane without the need for energy from the cell. It includes processes such as diffusion, where substances move from an area of higher concentration to an area of lower concentration, and facilitated diffusion, where substances move down a concentration gradient through specific protein channels in the membrane.
- Active Transport: In this process, cells expend energy to move drugs across the membrane against a concentration gradient. This includes the use of transport proteins that are energized by ATP to carry substances into or out of the cell.
- Vesicle Transport: Large molecules are moved across the membrane in bubble-like vesicles. This includes processes such as endocytosis (intake of substances) and exocytosis (expulsion of substances) which involve the membrane forming a vesicle around the substance to be transported.
These mechanisms are vital for the proper functioning of cells and the effectiveness of drug treatments. For instance, the majority of commercial drugs utilize passive diffusion to be absorbed into the body.