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

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. Diffusion of water through a selectively permeable membrane (passive)
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.