Upload
elmer-rodgers
View
217
Download
0
Embed Size (px)
Citation preview
QUIZ:Which organelle:1.Makes proteins2.Packages and ships proteins3.Makes ATP from carbohydrates4.Define amphipathic.5.Labels:A.B.C.D.E.
A B
ED
C
Membrane Transport
Passive: osmosis, diffusionActive: endocytosis, exocytosis
Concentration gradient drives the NET movement of molecules
Molecules move randomly and continuously. Impacts change their direction.
High Low
Permeability
Osmosis
Movement of water across a membrane from high concentration to low concentration
The greater (steeper) the concentration gradient, the faster the rate of diffusion.
Another rule of thumb:
InsideCell
OutsideCell
Con
cent
ratio
n of
sol
utes Cell A will diffuse faster
Cell A
Cell B
Effect of temperature on diffusion
Cell B will diffuse faster
Cell A
Cell B
Cell A Cell B
Tem
pera
ture
°C 22°
38°
Active Transport
© Brooks/Cole - Thomson Learning
Sodium-potassium Pump
© Brooks/Cole - Thomson Learning
3 factors that affect movement of molecules across membranes
• Effect of ConcentrationEffect of Concentration: the greater the concentration difference across the membrane, the faster the rate of diffusion (agar blocks)
• Effect of TemperatureEffect of Temperature: the higher the temperature, the faster the rate of diffusion due to increased energy of solute molecules (agar blocks)
• Effect of Pore SizeEffect of Pore Size: only solutes small enough to pass through the pores of a membrane are able to diffuse (dialysis: iodine moved in, glucose moved out, starch remained in)
Objective 3: Recognize the role of water potential in regulating the movement of water across membranes and note factors that affect water potential.
Objective 4: Describe the tonicity of biological solutions
Water potential: the potential energy of a volume of water; expressed as a pressure
Definitions
Osmosis - the diffusion of water
across membranes
Which way will the water go?
Definitions
• Solute - the substance dissolved in a liquid (e.g., sugar, salt)
• Solvent - the liquid in which the solute is dissolved (e.g., water)
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this p icture.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
“Free” water molecules can pass through membrane.
These solute molecules are too big to pass through membrane.
Higher water potential Lower water potential
• Hypotonic - solution that contains FEWER solute particles than another solution
• Hypertonic - solution that contains MORE solute particles than another solution
Obj. 4: Tonicity of solutions
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
Rule of Thumb• The net movement of WATERWATER is from hypotonichypotonic conditions to hypertonichypertonic conditions.
• If two systems are equal in the number of dissolved particles, they are said to be isotonicisotonic and no net change in volumes will occur.
Hypotonic Hypertonic
Notes on Diffusion and Osmosis
• Both solutes and solvents (water) can diffuse across a membrane and the concentration difference will eventually equalize • We are interested in the period of time before the system equalizes (becomes isotonic), to observe which direction diffusion is occurring• Always pay attention to both solutes and solvents in a question - both may be important!
Objective 5: Recognize the role of the cell wall and of the vacuole in producing turgor pressure to maintain the shape of the plant cell.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
Distilled water
Salt water
HIGH turgor pressure
LOW turgor pressure
Cell and cell wall do not change size.Vacuole swells and shrinks.
The pressure that develops between the cell wall and vacuole is called TURGOR pressure.
Plant cells ONLY
Egg inDistilled water
Egg inSugar water
H2O
H2O
Distilled water
H2O
Sugar water
H2O
Water is hypOtonicEgg is hypERtonic
Water is hypERtonicEgg is hypOtonic
Water moves from hypotonichypotonic conditions to hypertonichypertonic conditions.
Discussion questions
Many hospital patients receive intravenous liquids to replace body fluids. These liquids are generally complex solutions of salts and sugars. If all the patient needs is fluid, why doesn’t the physician simply inject pure water?
Why can’t we drink salt water?
Dialysis tubing is a model for a cell membrane.
Iodine solution
Starch & glucose
Dialysis tubing is a model for a cell membrane.
Iodine solution
Starch & glucose
Iodine + starch=blue
IodineGlucose
Cells have a selectively permeable membrane
Predict the effects of temperature and concentration gradients on diffusion rates
Concentration gradients
5% 0.5%
Started with 0%, diffused 5%Started with 0%, diffused 0.5%
5 - 0 = 5 0.5 - 0 = 0.5
Much greater concentration gradient
Sodium hydroxide solution
Agar Blocks