Chapter 5: Homeostasis and Transport

1. Chapter 5: Homeostasis and Transport 5-1 Passive Transport 5-2 Active Transport

2. 5-1 Passive Transport I. Diffusion (i.e., kinetic NRG of molecules) • Movement of X from [HIGH] to [LOW]. (1) Passive Transport (e.g., diffusion, osmosis) • Movement down a gradient, w/o using NRG.

4. (2) Concentration Gradient (required for diffusion) • DIFFERENCE in concentration; [HIGH] to [LOW].

5. (A) Equilibrium (RESULT of diffusion) • UNIFORM distribution over time.

7. (B) Diffusion Across Membranes • TWO conditions: (1) SIZE? (2) CHARGE? Ex: CO2 and O2, are small and easily diffuse through the bilayer.

8. Critical Thinking (1)A gelatin block is prepared with a CHEMICAL INDICATOR that turns PINK in the presence of a BASE. The block is enclosed in a MEMBRANE and placed in a beaker of AMMONIUM HYDROXIDE solution. After 30 minutes, the block begins to TURN pink. What may have occurred to PRODUCE this observable result?

9. II. Osmosis (i.e., diffusion of WATER) • WATER moves from LOW [OAS] to HIGH [OAS] NOTE: OAS: Osmotically Active Substance (a solute); salts, sugars, or proteins.

10. Critical Thinking (2)Sea water has a HIGHER concentration of SOLUTES than do human body cells. Why might drinking large amounts of SEA WATER be DANGEROUS for the human body’s equilibrium?

13. (A) Direction of Osmosis (NET direction of water) • Water moves towards the OAS (where there is LESS water).

16. (1) Hypotonic ([OAS]CELL > [OAS]SOLUTION ) • Cell SWELLS  WATER into cell FROM solution. (Ex: Red Blood Cell in dH2O)

20. (2) Hypertonic ([OAS]SOLUTION > [OAS]CELL) • Cell SHRINKS  WATER out of cell INTO solution. (Ex: Red Blood Cell in salt H2O)

24. (3) Isotonic ([OAS]CELL = [OAS]SOLUTION) • Cell shape is contant due to EQUAL water into AND out of cell. (Ex: Red Blood Cell in isotonic H2O)

26. (B) How Cells DEAL With Osmosis • Too much salt OR too little salt can be fatal for cells.

28. (1) Contractile Vacuoles (found in freshwater protists) • Collects and PUMPS out EXCESS water using NRG. (i.e., NOT osmosis, pumping AGAINST gradient)

29. Critical Thinking (3)Sometimes water SEEPS through the concrete WALL of a basement after a heavy rain, and the homeowner must REMOVE it with a sump pump. HOW can this situation be compared to the action of a unicellular organism that inhabits a freshwater pond?

31. (2) Turgor Pressure (inside central vacuole of PLANT cells) • Pressure of water AGAINST a plant CELL WALL due to a HYPOTONIC surrounding.

33. Critical Thinking (4)There is a HIGHER concentration of air molecules INSIDE an inflated balloon than there is outside the balloon. Because of their constant random motion, the molecules inside press against the balloon and keep it taut. How is the pressure exerted by these air molecules SIMILAR to TURGOR PRESSURE? How might it be DIFFERENT?

35. (3) Plasmolysis (i.e., plant cell COLLAPSING) • Turgor pressure is LOST and cell membrane COLLAPSES from plant cell wall. (i.e., wilting of plants becoming DEHYDRATED)

38. (4) Cytolysis (i.e., animal cell BURSTING) • Cell cannot stop movement of water INTO itself; cell swells and lyses. (Ex: Red Blood Cells in Hypotonic: Hemolysis)

40. III. Facilitated Diffusion (e.g., glucose) • ASSISTED by membrane proteins; “CARRIER proteins.” Ex: Glucose is TOO LARGE for SIMPLE diffusion through the bilayer.

42. (1) Carrier Proteins (e.g., integral proteins) • Move molecules down their gradient WITHOUT use of NRG.

44. IV. Diffusion Through Ion Channels (usually always OPEN) • Move IONS across the cell membrane due to their charge.

46. (1) Ion Channels allow ions to pass through bilayer BUT are specific to serve only certain ions. Common ions include… Na+, K+, Ca+2, and Cl- • Gated-Ion Channels open AND close in response to 3 types of stimuli: • Electrical Signals (Nerve Impulses) • Chemical Signals in the Cytosol • Chemical Signals in the ECM