Cellular Transport

1. Cellular Transport

2. Define HOMEOSTASIS • Maintaining a relatively constant or stable internal environment, even when external conditions change dramatically

3. Give the function of each of the following organelles • Cell (plasma) membrane • a flexible boundary between a cell and its environment • allows nutrients into the cell no matter what the external conditions are.

4. Give the function of each of the following organelles • Lysosome • Clean up crew – break down organelles that have outlived their usefulness • Break down lipids, carbs, proteins • Golgi Apparatus • Modifies, sorts and packages proteins and other materials from the ER for storage in cell or release outside of cell

5. Homeostasis and Transport Intro • How does the cell membrane maintain homeostasis? • Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells • Label and describe as many parts/features of the cell membrane as you can:

6. Components of Cell Membrane:

7. Key Terms Associated with Transport: • Concentration Gradient - difference in amount of molecules across space • Down the concentration gradient: • Higher Concentration  Lower Concentration • Up the concentration gradient: • Lower Concentration Higher Concentration • Equilibrium - when the concentration is the same throughout

8. Concentration Gradient:

9. Types of Transport: • Passive Transport– movement of molecules down their concentration gradient without the use of energy • Active Transport-movement of molecules up their concentration gradient with the use of energy

10. Passive and Active Transport

11. 4 Types of Passive Transport Diffusion Osmosis Facilitated Diffusion (Diffusion) Ion channels Passive Transport: • Determining Factors • Size • Type of Molecule • Chemical Nature of membrane • Small, nonpolar, hydrophobic molecules

12. Diffusion:

13. Diffusion: • Process by which molecules tend to move from an area where they are more concentrated to an area where they are less concentrated (passive)

14. Osmosis: • Diffusion of water through a selectively permeable membrane (passive) • (from an area of higher water concentration to an area of lower water concentration)

15. Osmosis:

16. Diffusion vs. Osmosis

17. Solutions Can Be: • Isotonic - solute concentration same on each side of membrane • No net change in cell size

18. Solutions Can Be: • Hypotonic - Solution with a solute concentration lower than cell • Water will diffuse into cell until equilibrium • The cell swells and may burst

19. Solutions Can Be: • Hypertonic- Solution with a solute concentration higher than the cell • Water will diffuse out cell until equilibrium • The cell shrinks

20. Effects of Osmosis: • Water diffuses from a hypotonic to a hypertonic solution

21. Dealing with Osmosis: • Plants (root cells) swell in a hypotonic environment • The swelling stops when the cell membrane is pressed against the cell wall • The cell wall is strong enough to resist the pressure, called turgor pressure • (pressure exerted against the cell wall in a hypotonic environment)

22. Cytolysis and Plasmolysis: • Cytolysis – In a hypotonic solution, cells can swell and eventually burst • Plasmolysis - In a hypertonic environment, water leaves the cell and the cell shrinks away from the cell wall as turgor pressure is lost

23. Contractile Vacuole: • Unicellular freshwater organisms (Paramecium) live in a hypotonic environment • Contractile Vacuole - collects excess water and pumps it out of cell

24. Review Questions: • 1. Toward what condition does diffusion eventually lead, in the absence of other influences? • 2. How is osmosis related to diffusion? • 3. If the concentration of solute molecules outside a cell is lower than the concentration in the cytoplasm, is the external solution hypotonic, hypertonic, or isotonic to the cytosol? • 4. Sea water has a higher concentration of solutes than do human body cells. Why might drinking large amounts of sea water be dangerous to humans?

25. Facilitated Diffusion • Movement of specific molecules across cell membranes through protein channels (passive) • (diffusion of materials across a cell membrane assisted by carrier proteins)

26. Facilitated Diffusion • Move molecules, (that cannot diffuse easily), down their concentration gradient • Move into or out of cell • Examples: Glucose, Amino Acids, Ions, Polar molecules (water) • Assisted by carrier proteins on the membrane • Specific to one type molecule • More protein=faster diffusion

27. Facilitated Diffusion of Glucose:

28. Ion Channels—Na+, K+, Ca2+, Cl- • Provide protein channels for ions to diffuse • Specific to Ion • Two types • Open • Gated—open and close in response to specific stimuli

29. Active Transport: • Cells use energy to move up concentration gradient • ATP supplies energy • Carrier proteins act as pump

30. SODIUM-POTASSIUM PUMP: • In animal cells transport Na+ and K+ up the Concentration Gradient • 3 Na+ moved outside of cell • 2 K+ moved inside cell

31. Steps for Transport • 3 Na+ bind to carrier protein in cytoplasm • Carrier protein splits phosphate group from ATP • P group binds with carrier protein—shape changes—releases Na+ • Now can pick up 2 K+ on outside • Carrier protein changes shape releases K+

32. Exocytosis and Endocytosis: • Transport large molecules across membrane • Transport a large amount of small molecules • Energy used

33. Exocytosis: • Exporting large molecules outside of cell • Process • Packaged in Golgi Apparatus • Vesicle transports to cell membrane • Vesicle fuses to membrane • Contents released • Vesicle becomes part of membrane

34. Endocytosis: • Cells take in (ingest) substances • Process • Depression in cell membrane folds in enclosing material from outside of the cell • Pinched off forming a membrane-bound vesicle • Vesicle fuses with lysosomes • Fuse with other organelles

35. 3 Types of Endocytosis: • Pinocytosis—”Cell Drinking” • Ingestion of tiny droplets • Phagocytosis-”Cell Eating” • Engulfs large, solid molecule or whole cells (like bacteria) • Receptor-mediated—Specific • Ingestion of specific substances that bind to receptor proteins on specialized areas of cell membrane

36. 3 Types of Endocytosis:

37. Review Questions: • 1. Explain the difference between passive and active transport. • 2. What provides the energy that drives the sodium-potassium pump? • 3. Explain the difference between phagocytosis and pinocytosis. • 4. During intense exercise, potassium tends to accumulate in the fluid surrounding muscle cells. What membrane protein helps muscle cells counteract this tendency? Explain your answer.