Transcript CP-7.4-Diffusion

Chapter 7, section 7.4
Cell Transport
Plasma membrane
• Homeostasis
• Selectively permeable
Cellular Transport!
• Molecules move from one
side of cell to the other
• Two Types
–Passive
–Active
Cellular Structure and Function
Passive Transport
 Movement of particles across the cell
membrane without using energy
Three Modes of Passive Transport
 Diffusion
 Osmosis
 Facilitated Diffusion
Concentration Gradient
• Difference in quantities of molecules
across a distance
• Movement continues until equilibrium
is reached
Equilibrium
• when the concentrations of diffusing
substances becomes equal on both
sides
Cellular Structure and Function
Diffusion
 Movement of particles from an area of high
concentration to an area of lower
concentration
Initial Conditions
Sugar cube
Diffusion
Low
High
High
Low
Cellular Structure and Function
 Diffusion is controlled by
 Temperature
 Pressure
 Concentration
 Diffusion continues until dynamic
equilibrium is reached
Video: Dynamic Equilibrium
• http://player.discoveryeducation.com/ind
ex.cfm?guidAssetId=58F2933C-10EA47BF-844AAE2109A5226A&blnFromSearch=1&pr
oductcode=US
• 6:07 min.
Cellular Structure and Function
Simple Diffusion is a type of diffusion
Molecules move freely across membrane
• Depends upon:
– 1. Size of molecule
– 2. Type of molecule
– 3. Charge of molecule
– 4. Type of membrane
Simple
Diffusion
Smelly balloons! Activity.
Diffusion and Osmosis
• Solution
Osmosis
– 1. Solvent
• What the solute dissolves in
• Water is Universal Solvent
– 2. Solute
• What dissolves in/moves through the solvent
Sugar cube
Cellular Structure and Function
Osmosis
 Diffusion of water across a selectively
permeable membrane
•Moves from [high] to [low]
•Occurs until equilibrium.
Three Types of Solutions
 Isotonic
 Hypotonic
 Hypertonic
Solutions:
• Hypertonic
– more solute in solution
• Hypotonic
– more solute in cell
• Isotonic
– the same solute amount in cell and
solution
Cellular Structure and Function
Hypertonic Solution
 Solute concentration is higher outside the
cell.
 Water diffuses out of the cell.
Plant Cell
Blood Cell
13,000x
Why do people….
• Gargle with salt
when they have a
soar throat?
Cellular Structure and Function
Hypotonic Solution
 Solute concentration is higher inside the cell.
 Water diffuses into the cell.
Plant Cell
Blood Cell
13,000x
Cellular Structure and Function
Isotonic Solution
 Water and dissolved substances diffuse
into and out of the cell at the same rate.
Plant Cell
Blood Cell
11,397x
How do cells deal with Osmosis?
• Contractile vacuoles
– Pump water out of cell
(active)
Effect of Water on RBC
shrivel
cytolyse
Osmosis in Plant Cells
Plasmolysis
• Observe
Elodea leaves
via a wet mount of the
sample
Hypertonic
10% NaCl
Distilled water
Hypotonic
Plasmolysis (wilt)
Hypertonic
How do cells deal?
• Plant environment is ___________.
• Water moves in via osmosis
• Creates Turgor pressure
– wilting (plasmolysis).
Carrot demo:
Predict what you think will occur: NaCl? Water?
Back to the carrot
• Carrot in normal water
– Iso? Hypo? Hyper?
• Carrot in NaCl
– Iso? Hypo? Hyper?
DO NOW:
• A cell is placed in a 60% salt solution.
Inside the cell is 50% water. Will the
water flow into the cell, out of the cell, or
not move at all?
60% salt
Outside cell
50% water
(inside cell)
How to determine…
• Which way water will flow.
• Convert salt concentration to water
concentration by subtracting the salt
concentration from 100%
• 100% - [salt] = [water]
Then…
• Compare the [water] concentrations
• Water will move from high to low
concentration
• Example:
5% salt
Outside cell
1% salt
(inside cell)
Tonicity
• Video-United Streaming
How to RBCs deal?
• RBCs lack pumps, cell walls and
vacuoles
• So how do they deal?
Self check:
Which on is hypotinic? Hypertonic? Isotonic?
Step 1
• Molecule binds to carrier protein
Step 2
• Carrier molecule changes shape
Step 3
• Molecule released on other side of
membrane
Step 4
• Returns to original shape
Cellular Transport
• Passive Transport
– Diffusion
– Osmosis
• Isotonic
• Hypertonic
• Hypotonic
– Facilitated Diffusion
Facilitated Diffusion is a type of Diffusion
But the particles need help getting through
the membrane
Facilitated Diffusion
• Facilitate
– “help” “ease”
• Used for molecules that cannot easily
pass through the membrane
– Not lipid soluble
– Too large
– Have a charge
Facilitated diffusion
• Movement of materials across the plasma
membrane using carrier proteins
• [High] to [low]
Cellular Structure and Function
Carrier Proteins
4 Steps
• Speeds up diffusion
• Allows for larger molecules to pass
through membrane
• Example: glucose transport
DO NOW!
• What is the difference between A, B,
and C? (ie What processes do these
figures represent?)
Active Transport
• Requires energy
• Moves molecules from low to high
concentration
Active Transport
 Movement of particles across the cell
membrane using energy (ATP)
Active Transport Using Carrier Proteins
Video
• Sodium-Potassium Pump
Movement of Substances across Cell Membranes
• Active Transport - sodium-potassium pump
Active Transport
• Sodium-Potassium Pump
• Endocytosis
– Pinocytosis
– Phagocytosis
• Exocytosis
 Na+/K+ ATPase pump
 Moves three Na+ ions out of the cell and
two K+ ions into the cell
 Moves against concentration gradients
-->
Sodium-Potassium Pump
• Important for:
– nerve impulses
– muscle control
Endocytosis and
Exocytosis
• passage of food and waste particles that
are too big to pass through the plasma
membrane and protein channels
Endocytosis
• Cells ingest (eat) external fluid,
macromolecules, large particles, & other
cells
Endocytosis
(endo- “inside”)
•
Membrane folds in and forms a vesicle
•
Contents are digested by cellular enzymes
lysosomes
• Pinocytosis
– Movement of fluids
• Phagocytosis
– Movement of large molecules or whole cells
Exocytosis - “excrete”
 Secretion of material out of the plasma
membrane
Exocytosis
1. Substance packaged into vesicle
2. Vesicle fuses with plasma membrane
3. Substance released from cell
Putting it all together
Passive
Transport
Active
Transport
DO NOW:
• What is going on here?