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Chapter 5 Miss Colabelli
Cell Transportmaintaining homeostasis
Passive Transport
Does NOT require any ATP or energy
Happens automatically
Channels may be used in cell membrane
Passive Transport
This type of transport moves from an area of high concentration to low concentration
Passive Transport
• Three types of passive transport
• Simple diffusion
• Osmosis
• Facilitated Diffusion
• These processes DO NOT REQUIRE ENERGY
Diffusion
Type of passive transport
When molecules move from an area of higher concentration to an area of lower concentration until equilibrium is met
http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP1903
What affects the rate of diffusion?
Concentration of the solution
Temperature of the solution
Pressure also speeds up particle motion
Concentration
The amount of dissolved solute in a solution
Molecules will move to an area less concentrated
Molecules diffuse through the cell membrane of cells
Concentration gradient
The difference in concentration in a solution between a cell and its surroundings
Concentration Gradient
No gradient - even distribution
Concentration to the right
Increase Rate of Diffusion
Temperature
Molecules move faster in higher temperatures
Pressure
Increasing pressure also increases rate of diffusion
EquilibriumThis occurs when there is no longer a concentration gradient
Molecules are evenly dispersed but still continue to move randomly
Cell Membrane
Movement through membrane
Cell membrane is surrounded by water
Phospholipid bilayer
Cell Membrane
Forms by itself in water
Proteins imbedded
Markers
Receptors
Channels
Diffusion in cells
Small molecules diffuse in and out of the cell to reach equilibrium on both side of the membrane
OsmosisDiffusion of water across a biological membrane
From an area of high concentration to low concentration of WATER
Comparing concentrations
Osmosis in Cells
Cells are surrounded and filled with water
Water can move freely through the membrane
http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP11003
Direction of Osmosis
Hypertonic
Outside cell is more concentrated than the cell
ex:
The solution with 20% salt is hypertonic compared to the 10% salt solution
20% salt solution outside the cell
10% salt solution inside the cell
Hypotonic
Outside the cell is less concentrated than cell
ex:
The solution with 10% salt is hypotonic compared to the 20% salt solution
10% salt solution outside the cell
20% salt solution inside the cell
Isotonic
Equal concentrations
ex:
Equilibrium is reached
10% salt solution outside the cell
10% salt solution inside the cell
Osmotic Pressure
Net movement of water into cells
Determined by solute concentration
Osmosis - hypertonic
Higher solute concentration in solution
Ex: a cell in salt water
When molecules are too large to fit through cell membrane or protein channels
Water will diffuse OUT of the cell to reach equilibrium
Cell shrinks
Osmosis - hypotonic
Lower solute concentration in solution
Ex: a cell in pure water
If molecules are too large to fit through cell membrane or protein channels
Water will diffuse INTO the cell to reach equilibrium
Cell swells - may burst!
Osmosis - IsotonicEqual concentration in solution
If molecules are too large to fit through cell membrane or protein channels
Water will diffuse IN AND OUT of the cell to maintain equilibrium
Osmosis in Plant Cells
Turgor Pressure
Pressure on the walls of the plant cells due to vacuole filling
Increase in turgor pressure is due to an increase of water to cell
Plasmolysis
When a cell shrinks due to lack of water
Red Onion Cells - Isotonic
Red Onion Cells - Hypertonic
Red Onion Cells - Hypotonic
Facilitated DiffusionWhen the cell membrane has protein channels (carrier proteins) where materials are transported in or out of cell
NO energy needed for this process
http://www.youtube.com/watch?v=-Ul2oJ_TkNw
Active Transport
Against concentration gradient
From an area of low concentration to an area of high concentration
Requires cell energy (ATP) because you’re going AGAINST concentration gradient
3 types of active transport
Three types of active transport
Active transport
Endocytosis
Exocytosis
These processes REQUIRE ENERGY
Active Transport
Protein channels embedded in cell membrane
Gated channels
Need energy to open
Protein changes shape when energy is used
Sodium/Potassium Pump
Step 1: 3 sodium ions bind to carrier protein
Step 2: ATP binds to carrier protein and changes shape allowing Na+ to move out of the cell
Step 3: 2 potassium ions move into carrier protein
Step 4: ATP binds to carrier protein and changes shape allowing K+ to move into the cell
http://www.youtube.com/watch?v=GTHWig1vOnY
Sodium/Potassium Pump
Sodium Potassium Pump
Movement in Vesicles
Endocytosis - INTO the cell
Cell membrane is used to create a vesicle around particles
Phagocytosis
Particle ingestion
Pinocytosis
Liquid ingestion
Movement in Vesicles
Exocytosis - OUT of the cell
Vesicles created in the cell fuse with cell membrane and release particles/liquids
Known as bulk transport