1. End Show Slide 1 of 47 Copyright Pearson Prentice Hall 7-3 Cell Boundaries

2. End Show 7-3 Cell Boundaries Slide 2 of 47 Copyright Pearson Prentice Hall 7-3 Cell Boundaries All cells are surrounded by a thin, flexible barrier known as the cell membrane. Many cells also produce a strong supporting layer around the membrane known as a cell wall.

3. End Show 7-3 Cell Boundaries Slide 3 of 47 Cell Membrane The cell membrane Regulates what enters and leaves the cell Provides protection and support. Copyright Pearson Prentice Hall Cell Membrane

4. End Show 7-3 Cell Boundaries Slide 4 of 47 Copyright Pearson Prentice Hall Cell Membrane Outside of cell Cell membrane Inside of cell (cytoplasm) Protein channel Proteins Lipid bilayer Carbohydrate chains

5. End Show 7-3 Cell Boundaries Slide 5 of 47 Copyright Pearson Prentice Hall Cell Walls What is the main function of the cell wall? It supports and protects the cell.

6. End Show Slide 6 of 47 Diffusion through Cell Boundaries: Every living cell exists in a liquid environment. For example, cactus plants scorpions all have liquid within them. Copyright Pearson Prentice Hall

7. End Show 7-3 Cell Boundaries Slide 7 of 47 Copyright Pearson Prentice Hall Diffusion Through Cell Boundaries Measuring Concentration A solution is a mixture of two or more substances. The substances dissolved in the solution are called solutes. The concentration of a solution is the mass of solute in a given volume of solution, or mass/volume. 4 g/L is more concentrated than 2 g/L.

8. End Show 7-3 Cell Boundaries Slide 8 of 47 Copyright Pearson Prentice Hall Diffusion Through Cell Boundaries What happens during diffusion?

9. End Show 7-3 Cell Boundaries Slide 9 of 47 Copyright Pearson Prentice Hall Diffusion Through Cell Boundaries Diffusion Is when particles (or solutes) in a solution tend to move from an area where they are more concentrated (4 g/L) to an area where they are less concentrated (2 g/L). When the concentration of the solute is the same throughout a system, the system has reached equilibrium.

10. End Show Slide 10 of 47 What does diffusion and equilibrium have to do with cell membranes? Suppose a substance is present in unequal concentrations on either side of a cell membrane. If the substance can cross the cell membrane, it’s particles will tend to move toward the area where it is less concentrated until equilibrium is reached. At that point, the concentration of the substance on both sides of the cell membrane will be the same. Copyright Pearson Prentice Hall

11. End Show 7-3 Cell Boundaries Slide 11 of 47 Copyright Pearson Prentice Hall Diffusion Through Cell Boundaries

12. End Show 7-3 Cell Boundaries Slide 12 of 47 Copyright Pearson Prentice Hall Osmosis What is osmosis?

13. End Show 7-3 Cell Boundaries Slide 13 of 47 Copyright Pearson Prentice Hall Osmosis Osmosis is the diffusion of water through a selectively permeable membrane. Remember our EGG lab?

14. End Show 7-3 Cell Boundaries Slide 14 of 47 Copyright Pearson Prentice Hall Osmosis How Osmosis Works Movement of water Dilute sugar solution (Water more concentrated) Concentrated sugar solution (Water less concentrated) Sugar molecules Selectively permeable membrane

15. End Show 7-3 Cell Boundaries Slide 15 of 47 Copyright Pearson Prentice Hall Osmosis Water tends to diffuse from a highly concentrated region to a less concentrated region. If you compare two solutions, three terms can be used to describe the concentrations: Hypotonic solution (Example: Water). Water enters the cell. Hypertonic solution (Example: Corn Syrup). Water leaves cell. isotonic (”same strength”) Solutes are the same inside and outside of a cell

16. End Show 7-3 Cell Boundaries Slide 16 of 47 Copyright Pearson Prentice Hall Facilitated Diffusion Facilitated Diffusion: Where sugar glucose can pass through the membrane with the help of a protein channel. Protein channel Glucose molecules

17. End Show 7-3 Cell Boundaries Slide 17 of 47 Copyright Pearson Prentice Hall Active Transport Active Transport (3 Types: Molecular, Endocytosis, and Exocytosis) In active transport, cells move materials in the opposite direction from which the materials would normally move—that is against a concentration difference. Active transport requires energy.

18. End Show 7-3 Cell Boundaries Slide 18 of 47 Copyright Pearson Prentice Hall Active Transport Molecular Transport In active transport, small molecules and ions are carried across membranes by proteins in the membrane.

19. End Show 7-3 Cell Boundaries Slide 19 of 47 Copyright Pearson Prentice Hall Active Transport Molecule to be carried Active Transport Molecular Transport

20. End Show 7-3 Cell Boundaries Slide 20 of 47 Copyright Pearson Prentice Hall Active Transport Endocytosis and Exocytosis Endocytosis is the process of taking material into the cell. Two examples of endocytosis are: Phagocytosis: “Cell eating.” Pinocytosis: Cells taking up fluid from the surrounding environment. During exocytosis, materials exit the cell.

21. End Show - or - Continue to: Click to Launch: Slide 21 of 47 Copyright Pearson Prentice Hall 7-3

22. End Show Slide 22 of 47 Copyright Pearson Prentice Hall 7-3 Unlike a cell wall, a cell membrane a.is composed of a lipid bilayer. b.provides rigid support for the surrounding cell. c.allows most small molecules and ions to pass through easily. d.is found only in plants, fungi, algae, and many prokaryotes.

23. End Show Slide 23 of 47 Copyright Pearson Prentice Hall 7-3 The concentration of a solution is defined as the a.volume of solute in a given mass of solution. b.mass of solute in a given volume of solution. c.mass of solution in a given volume of solute. d.volume of solution in a given mass of solute.

24. End Show Slide 24 of 47 Copyright Pearson Prentice Hall 7-3 If a substance is more highly concentrated outside the cell than inside the cell and the substance can move through the cell membrane, the substance will a.move by diffusion from inside the cell to outside. b.remain in high concentration outside the cell. c.move by diffusion from outside to inside the cell. d.cause water to enter the cell by osmosis.

25. End Show Slide 25 of 47 Copyright Pearson Prentice Hall 7-3 The movement of materials in a cell against a concentration difference is called a.facilitated diffusion. b.active transport. c.osmosis. d.diffusion.

26. End Show Slide 26 of 47 Copyright Pearson Prentice Hall 7-3 The process by which molecules diffuse across a membrane through protein channels is called a.active transport. b.endocytosis. c.facilitated diffusion. d.osmosis.