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 which maintains homeostasis and also provides protection and support for cells without a cell wall. 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 7-3 Cell Boundaries Composition of Cell Membrane: 1. Lipid Bilayer: double layered sheet which is a flexible structure that forms a strong barrier between the cell and its surroundings

6. End Show 7-3 Cell Boundaries Slide 6 of 47 Phospholipids - contain one phosphate group, one glycerol, and 2 fatty acids. Main component of cell membranes. Copyright Pearson Prentice Hall

7. End Show 7-3 Cell Boundaries Slide 7 of 47 Copyright Pearson Prentice Hall 7-3 Cell Boundaries Composition of Cell Membrane: 2. Protein molecules are embedded in the lipid bilayer. Carbohydrates attached to the proteins act like chemical identification cards allowing cells to identify each other. Some proteins form channels and pumps to help move material into and out of the cell

8. End Show 7-3 Cell Boundaries Slide 8 of 47 3. Most cells are selectively permeable, meaning that some substances can pass across them and some cannot. Copyright Pearson Prentice Hall

9. End Show 7-3 Cell Boundaries Slide 9 of 47 Cell Walls Copyright Pearson Prentice Hall Cell Wall Cell walls are found in plants, algae, fungi, some protists and many prokaryotes.

10. End Show 7-3 Cell Boundaries Slide 10 of 47 Cell walls have openings or pores to allow water, oxygen, carbon dioxide and other materials to pass through. They lie outside the cell membrane. They give structure and support – the thicker the cell wall the more stiff or rigid the structure will be. Copyright Pearson Prentice Hall

11. End Show 7-3 Cell Boundaries Slide 11 of 47 Copyright Pearson Prentice Hall Cell Walls What is the main function of the cell wall?

12. End Show 7-3 Cell Boundaries Slide 12 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.

13. End Show 7-3 Cell Boundaries Slide 13 of 47 Copyright Pearson Prentice Hall Diffusion Through Cell Boundaries What happens during diffusion? - Molecules MOVE!!!! - Molecules are always in motion. They move around and bump into each other.

14. End Show 7-3 Cell Boundaries Slide 14 of 47 Copyright Pearson Prentice Hall Diffusion Through Cell Boundaries Diffusion Particles in a solution tend to move from an area where they are more concentrated to an area where they are less concentrated. This process is called diffusion. When the concentration of the solute inside the cell is the same as the concentration outside the cell, the cell and its environment has reached equilibrium.

15. End Show 7-3 Cell Boundaries Slide 15 of 47 Copyright Pearson Prentice Hall Diffusion Through Cell Boundaries

16. End Show 7-3 Cell Boundaries Slide 16 of 47 Copyright Pearson Prentice Hall Osmosis Osmosis is the diffusion of water through a selectively permeable membrane. Whenever water moves, into or out of the cell, we call it osmosis.

17. End Show 7-3 Cell Boundaries Slide 17 of 47 Copyright Pearson Prentice Hall Osmosis How Osmosis Works Movement of water from high concentration to low concentration Dilute sugar solution (Water more concentrated) Concentrated sugar solution (Water less concentrated) Sugar molecules Selectively permeable membrane (only water can move)

18. End Show 7-3 Cell Boundaries Slide 18 of 47 Copyright Pearson Prentice Hall Osmosis In osmosis, water tends to diffuse from a highly concentrated region to a less concentrated region. If you compare solutions, three terms can be used to describe the concentrations of the solution due to the amount of solute dissolved in the water: - hypertonic (“above strength”)more solute/less water. - hypotonic (“below strength”)less solute/more water. - isotonic (”same strength”)same amount of solute

19. End Show 7-3 Cell Boundaries Slide 19 of 47 Copyright Pearson Prentice Hall Osmosis Osmotic Pressure Osmosis exerts a pressure known as osmotic pressure on the cell compared to its environment. Remember both inside the cell and outside the cell there is a concentration. It is the water that moves!!

20. End Show 7-3 Cell Boundaries Slide 20 of 47 Copyright Pearson Prentice Hall Osmosis What is osmosis?

21. End Show 7-3 Cell Boundaries Slide 21 of 47 Copyright Pearson Prentice Hall Facilitated Diffusion Facilitated Diffusion requires no energy because molecules still move from a higher to a lower concentration. Each protein channel is specific for the type of molecule that it allows to enter the cell. Protein channel Glucose molecules High Concentration Low Concentration

22. End Show 7-3 Cell Boundaries Slide 22 of 47 Copyright Pearson Prentice Hall Active Transport Sometimes cells move materials in the opposite direction from which the materials would normally move—that is against a concentration difference. This process is known as active transport. Active transport requires energy!

23. End Show 7-3 Cell Boundaries Slide 23 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. Energy use in these systems enables cells to concentrate substances in a particular location, even when diffusion might move them in the opposite direction.

24. End Show 7-3 Cell Boundaries Slide 24 of 47 Copyright Pearson Prentice Hall Active Transport Molecule to be carried Active Transport Molecular Transport

25. End Show 7-3 Cell Boundaries Slide 25 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 (takes in food) Pinocytosis (takes in water)

26. End Show 7-3 Cell Boundaries Slide 26 of 47 During exocytosis, materials are forced out of the cell. “Exo” = exit “Cyto” = cell Copyright Pearson Prentice Hall

27. End Show Slide 27 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.

28. End Show Slide 28 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.

29. End Show Slide 29 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.

30. End Show Slide 30 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.

31. End Show Slide 31 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.