Describe the transport mechanism
The transport mechanism is the process by which molecules and ions are moved across cell membranes to enter or exit cells. There are two main types of transport mechanisms: passive transport, which does not require energy, and active transport, which requires energy in the form of ATP.
Passive transport includes simple diffusion, facilitated diffusion, and osmosis. In simple diffusion, molecules move from an area of high concentration to low concentration across the cell membrane. Facilitated diffusion involves the use of carrier proteins or channels to assist in the movement of molecules across the membrane. Osmosis is the movement of water across a selectively permeable membrane to balance the concentration of solutes on either side of the membrane.
Active transport requires energy as molecules are moved against their concentration gradient. This process is carried out by transport proteins called pumps, such as the sodium-potassium pump, which uses ATP to move ions across the membrane. Another type of active transport is endocytosis, where large molecules are engulfed by the cell membrane and brought into the cell through vesicles. Exocytosis is the opposite process, where molecules are expelled from the cell through vesicles fusing with the cell membrane.