The beaker in the illustration contains two solutions of charged particles (salt) with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that has similar properties to the plasma membranes we discussed in class.

Statement 1: The direction of diffusion of a solute across a membrane is determined by its concentration gradient and always moves toward equilibrium. Statement 2: In passive transport, solutes move down the gradient from a region of low concentration to a region of high concentration. A Both statements are true. Both statements are false. C) Statement 1 is true. Statement 2 is false. Statement 1 is false. Statement 2 is true.

If two solutions separated by a semi-permeable membrane are isotonic, can you conclude that they are in chemical equilibrium?

The surface area to volume ratio affects the ability of the cell to exchange nutrients and waste products with the outside environment. Many factors affect the movement of molecules across the cell membrane, including membrane thickness, temperature, pressure, concentration gradient, molecular mass, distance travelled, solvent properties and surface area of the cell. In general, according to Einstein’s approximation equation (Equation 1), diffusion time is inversely proportional to the to the diffusion coefficient (D), where t is time and x is distance travelled. The diffusion coefficient is unique to each type of molecule and is determined experimentally. Waste products such as carbon dioxide (CO2) pose a unique problem to cells as their accumulation may be lethal. Exchange with the external environment is dependent upon the distance the waste must travel; for a round cell this will be up to half the cell diameter. Using the diffusion coefficient (D) for carbon dioxide (1.97 × 10-5…