Keystone Review Passive Transport. A – ATP is a source of energy, and facilitated diffusion does not require the input of energy. B – Facilitated diffusion relies on membrane proteins such as channels or carriers to move materials across the membrane.
B. No, the outcome depicted in diagram 2 is no a possible result of the original situation. Passive transport ceases once equilibrium has been reached. In order for the result in diagram 2 to occur, the cell would continue moving solute across the membrane after equilibrium has been reached.
C. Yes, the outcome depicted in diagram 3 is a possible result of the original situation. The membrane is impermeable to the solute, which cannot enter the cell through passive transport. Therefore, it remains outside the cell.
A. Concentration gradients cause passive transport to occur. If there is no concentration gradient, then equilibrium has been reached and passive transport will not occur. Active transport can create and maintain a concentration gradient through the use of energy.
B. In passive transport, materials move through the phospholipid bilayer if it is permeable to that substance. In active transport, the phospholipid bilayer forms vesicles that transport the materials contained inside, fusing with other membranes.
C. In passive transport, membrane proteins may allow molecules or ions through the membrane. They do not use energy and cannot move against the concentration gradient. In active transport, protein pumps use energy in the form of ATP to move substances against their concentration gradient. Membrane receptor proteins may also aid in endocytosis.