7-3 Cell Boundaries

1. 7-3 Cell Boundaries

2. Objectives Explain the significance of the selectively permeable membrane to the transport of molecules. Predict the movement of molecules across a selectively permeable membrane (diffusion, osmosis, active transport) needed for a cell to maintain homeostasis given concentration gradients and different size molecules. Explain how water is important to cells (body temp., soluble environment, reactant in chemical reaction, maintains turgidity).

3. Descriptors Identify that water is important to cells. Explain how water is important to cells. Predict movement of molecules across a selectively permeable membrane needed to maintain homeostasis. Compare and contrast process used in movement of molecules across a semipermeable membrane, taking energy use into consideration.

4. Review Cell Membrane – flexible barrier of cell that regulates what enters and leaves the cell. The cell membrane is “semipermeable”.

5. Cell Membrane & Cell Wall • Cell Membrane – flexible barrier of cell that regulates what enters and leaves the cell. • Cell Wall – protects cell and give cell structure. • Found only in plant cells.

6. Preview • What does semi -permeable mean? What does permeable mean?

7. How do things Move through and Between cells?!?

8. Introduction

9. Demonstration!

10. Diffusion In a solution, particles move constantly. Diffusion – tendency of particles to move from an area of high concentration to an area of low concentration.

11. Diffusion Pg. 184 Figure 7-14 When do the particles of solute stop moving? When the concentration of solute is the same throughout, and the system has reached equilibrium (homeostasis).

12. Osmosis Water diffuses across membranes more easily than other substances. Osmosis – diffusion of water across semi-permeable membrane.

13. Clicker Question #1 Which of the following is an example of diffusion? A student sprays perfume and it moves throughout the room. Food coloring is added to a beaker of water and slowly spreads during a science experiment. Both a and b are examples of diffusion. None of the above are examples of diffusion.

14. Clicker Question #2 During diffusion, particles move from… Area of high concentration to area of low concentration. Area of low concentration to area of high concentration. They don’t move…they’re just particles. Areas where they will explode

15. Diffusion & Osmosis How much energy does a cell use for diffusion? Cell uses ________ energy for materials to get into cell for DIFFUSION or OSMOSIS.

16. Brain Break – Happy Halloween

17. Homework & Closure • We have more to go for this section. • We will begin a lab later in the week. • Vocabulary for homework.

18. Objectives Explain the significance of the selectively permeable membrane to the transport of molecules. Predict the movement of molecules across a selectively permeable membrane (diffusion, osmosis, active transport) needed for a cell to maintain homeostasis given concentration gradients and different size molecules. Explain how water is important to cells (body temp., soluble environment, reactant in chemical reaction, maintains turgidity).

19. Descriptors Identify that water is important to cells. Explain how water is important to cells. Predict movement of molecules across a selectively permeable membrane needed to maintain homeostasis. Compare and contrast process used in movement of molecules across a semipermeable membrane, taking energy use into consideration.

20. Review • What is diffusion? • Why does diffusion occur? • What is osmosis?

21. In Your Mini Group of 3 Find out who is the oldest…hypertonic Find out who is in the middle…hypotonic Find out who is the youngest…isotonic

22. How Osmosis Works Pg. 185 Figure 7-15  • Three types of solutions: • Hypertonic – “above strength”

23. How Osmosis Works • Three types of solutions: • Hypertonic – “above strength” • Hypotonic – “below strength” • Isotonic – “same strength”

24. Osmotic Pressure Let’s look at an experiment For organisms to survive their cells must balance the intake of water, salts, sugars, and other molecules.

25. Sample Experiment

26. Review What is the difference between diffusion and osmosis? Which type of solution is considered “same strength”. Which type of solution is considered “above strength”. Which type of solution is considered “below strength”.

27. Closure • Don’t forget about the vocabulary worksheet from Monday. • Chap. 7 Review • Pg. 189 1-6 OMIT #5 • Pg. 197 20-23 • Wednesday/Thursday we’ll do a case study, finish notes (just a little left), and talk about hand washing lab, build cell transport foldable.

28. Objectives Describe the importance of selectively permeable membrane to the transport of molecules. Predict the movement of molecules across a selectively permeable membrane needed for a cell to maintain homeostasis. Explain how water is important to cells.

29. Review What is the difference between diffusion and osmosis? Which type of solution is considered “same strength”. Which type of solution is considered “above strength”. Which type of solution is considered “below strength”.

30. Osmotic Pressure pg. 186 What if a cell is placed into a hypertonic solution?

31. Osmotic Pressure pg. 186 What if a cell is placed into a hypotonic solution?

32. Osmotic Pressure pg. 186 What if a cell is placed into a isotonic solution?

33. Osmotic Pressure Hypertonic Isotonic Hypotonic So why don’t our cells burst open shrivel up?

34. Facilitated Diffusion • Some molecules seem to pass through the cell membrane more easily than they should. • Example: RBC’s have a glucose (sugar) channel that allows glucose to pass in and out. • Only glucose can pass through the channel.

35. Facilitated Diffusion • Facilitated Diffusion – is the diffusion of particles through protein channels. • Hundreds of channels have been found to allow only one specific material through. • Carbohydrates and sugars mostly Hyper link

36. Active Transport • The most common pump is the sodium (Na) – potassium (K) (salts) pump. • Active transport – transport of materials that requires energy. • Uses “pumps” that are found in the membrane.

37. Active Transport Hyper link Uses energy to move molecules from low to high concentration (against concentration gradient).

38. To Relieve Confusion… Passive Transport Active Transport • Diffusion • Osmosis • Facilitated Diffusion NO ENERGY REQUIRED!!! • Active Transport REQUIRES ENERGY!!!

39. Closure • Review questions: What do we call the diffusion of water? How do large molecules diffuse into a cell when they are too large to pass through the cell membrane? What is the difference between active transport and passive transport? What are three examples of passive transport? • Have a good weekend!