AP BIOLOGY

Detailed explanation-1: -All channel proteins and many carrier proteins allow solutes to cross the membrane only passively (“downhill”), a process called passive transport, or facilitated diffusion.

Detailed explanation-2: -An example of passive transport is diffusion, the movement of molecules from an area of high concentration to an area of low concentration. Carrier proteins and channel proteins are involved in facilitated diffusion.

Detailed explanation-3: -During active transport, substances move against the concentration gradient, from an area of low concentration to an area of high concentration. This process is “active” because it requires the use of energy (usually in the form of ATP). It is the opposite of passive transport.

Detailed explanation-4: -Symporter. A symporter uses the downhill movement of one solute species from high to low concentration to move another molecule uphill from low concentration to high concentration (against its concentration gradient). Both molecules are transported in the same direction.

Detailed explanation-5: -ACTIVE TRANSPORT It is also possible to move substances across membranes against their concentration gradient (from areas of low concentration to areas of high concentration).