Question

Bio 109-Osmosis and Diffusion b. What does it mean when the cell membrane is described as being selectively permeable? c. Distinguish between osmosis and diffusion. 5. Define the following terms: a. solute A Gubstance tnat is dissolvedina soluhon b. solvent The dissoluing ao a solu hoyn c. solution eneous mixture hun on d. organic molecule Revised 06/2011

Answer 1

b. A selectively permeable cell membrane is one that allows certain molecules, solutes or ions to pass through it by means of active or passive transport.

c. Diffusion is the process in which particles spread out from each other. They move from high concentration to an area of low concentration, down the concentration gradient until they are evenly distributed. Osmosis is very similar to diffusion but just for water. It is the movement of water into or out of a cell. Osmosis is the spontaneous net movement of water across a semipermeable membrane from a region of low solute concentration to a more concentrated solution, up a concentration gradient.

5

a. Solute: A solute is a solid, liquid, or gas which is dissolved to make a solution. A solute is dissolved in a solvent to make a solution.

b. Solvent: A solvent is a substance that dissolves a solute (a chemically distinct liquid, solid or gas), resulting in a solution. A solvent is generally a liquid but can also be a solid, a gas, or a supercritical fluid.

c. Solution: A solution is a homogeneous mixture of one or more solutes dissolved in a solvent.

d. Organic molecule: A molecule of the kind normally found in living systems. Organic molecules are usually composed of carbon atoms in rings or long chains, to which are attached other atoms of such elements as hydrogen, oxygen, and nitrogen. Four important classes of organic molecules—carbohydrates, lipids, proteins, and nucleic acids