The cell membrane regulates what enters and leaves the cell and provides protection. The cell wall provides support and protection for plant and bacterial cells. Diffusion is the movement of molecules from an area of higher concentration to lower concentration. Osmosis is the diffusion of water through a selectively permeable membrane, moving from an area of lower solute concentration to higher solute concentration.

1. Cell Boundaries 7.3

2. Cell Membrane Thin, flexible barrier around a cell; regulates what enters and leaves the cell.

3. Cell Wall Strong supporting layer around the cell membrane in plants, algae, and some bacteria.

4. Lipid BilayerDouble-layered sheet that forms the core of nearly all cell membranes.

5. ConcentrationThe mass of solute in a given volume of solution, or the mass/volume.

6. DiffusionProcess by which molecules tend to move from an area where they are more concentrated to an area where they less concentrated.

7. EquilibriumWhen the concentration of a solute is the same throughout a solution.

8. OsmosisDiffusion of water through a selectively permeable membrane.

9. Isotonic When the concentration of two solutions is the same.

10. Hypertonic When comparing two solutions, the solution with the greater concentrations of solutes.

11. HypotonicWhen comparing two solutions, the solution with the lesser concentration of solutes.

12. Facilitated Diffusion Movement of specific molecules across cell membranes through protein channels.

13. Active TransportEnergy-requiring process that moves material across a cell membrane against a concentration difference.

14. EndocytosisProcess by which a cell takes material into the cell by infolding of the cell membrane.

15. PhagocytosisProcess in which extensions of cytoplasm surround and engulf large particles and take them into the cell.

16. Pinocytosis Process in which a cell takes in liquid from the surrounding environment.

17. ExocytosisProcess by which a cell releases large amounts of material.

18. Key ConceptWhat are the main functions of the cell membrane and the cell wall?The cell membrane regulates what enters and leaves the cell and also provides protection and support. The main function of the cell wall is to provide support and protection for the cell.

19. Key ConceptWhat happens during diffusion?Because diffusion depends upon random particle movements, substances diffuse across membranes without requiring the cell to use energy.

20. Key ConceptWhat is osmosis?It is the diffusion of water through a selectively permeable membrane.