Cell membranes are selectively permeable, regulating which substances can pass through, as well as how much of each substance can enter or exit at a given time. In cells, some molecules can move down their concentration gradients by crossing the phospholipid portion of the membrane directly, while others must pass through membrane proteins. Which of these statements does NOT apply to facilitated diffusion?

Define the apical impulse and describe its normal location, size, and duration. which abnormal conditions may affect the location of the apical impulse? explain the mechanism producing normal first and second heart sounds. describe the effect of respiration on the heart sounds. describe the characteristics of the first heart sound and its intensity at the apex of the heart and at the base. describe the characteristics of the second heart sound and its intensity at the apex of the heart and at the base.