AP BIOLOGY

Detailed explanation-1: -To move substances against a concentration or electrochemical gradient, a cell must use energy. Active transport mechanisms do just this, expending energy (often in the form of ATP) to maintain the right concentrations of ions and molecules in living cells.

Detailed explanation-2: -Active transport is the process of moving molecules across a cellular membrane through the use of cellular energy. The alternative to active transport is passive transport, which uses kinetic energy only to move the molecules.

Detailed explanation-3: -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-4: -Active transport is the energy-requiring process of pumping molecules and ions across membranes against a concentration gradient.

Detailed explanation-5: -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.