AP BIOLOGY

Detailed explanation-1: -Passive Transport using Membrane Proteins These molecules need special transport proteins to help them move across the membrane, a process known as facilitated diffusion. These special proteins are called channel proteins or carrier proteins (Figure below), and they are attached to the cell membrane.

Detailed explanation-2: -Vesicle Transport Vesicles or other bodies in the cytoplasm move macromolecules or large particles across the plasma membrane. There are two types of vesicle transport, endocytosis and exocytosis (illustrated in Figure below). Both processes are active transport processes, requiring energy.

Detailed explanation-3: -If a substance must move into the cell against its concentration gradient, the cell must use free energy, often provided by ATP, and carrier proteins acting as pumps to move the substance. Substances that move across membranes by this mechanism, a process called active transport, include ions, such as Na+ and K+.

Detailed explanation-4: -Facilitated diffusion is diffusion that is helped along (facilitated by) a membrane transport channel. These channels are glycoproteins (proteins with carbohydrates attached) that allow molecules to pass through the membrane.