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7.3 Cell Transport Passive & Active
• Please turn to the page that looks like this!
Why does the cell transport materials?
• To maintain homeostasis!
Passive vs. Active
• What’s the difference?
• Energy!
ATP is Cell Energy!
• The movement of molecules across a membrane without energy input from the cell.
• ALWAYS high low concentration
• Movement of MOLECULES
• Ex: food coloring, perfume
• Movement of WATER specifically
* Movement is based on the natural kinetic energy of the particles!
In which direction will diffuse occur?
Solute molecules
Why?
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Simple Diffusion
• Requires NO energy
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DIFFUSION
Molecules move because they have a natural KINETIC ENERGY
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Diffusion of Liquids
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Diffusion through a Membrane
Cell membrane
Solute moves DOWN concentration gradient (HIGH to LOW)
Facilitated Diffusion
• What does the word “facilitate” mean?
• The diffusion of molecules across a membrane through transport PROTEINS. – Requires NO ENERGY input from the
cell
– ALWAYS moves molecules from highlow concentration • “DOWN the concentration gradient”
• REQUIRED for moving ions (have a charge), hydrophilic (“water-loving”) molecules, sugars (glucose), amino acids, and many others
OSMOSIS is a form of FACILITATED DIFFUSION
• Lipid bilayer is hydroPHOBIC
• Water has hard time passing directly through
• Special protein channels called AQUAPORINS allow water to pass through
• High Low concentration
**No energy needed
v Transport Protein
HIGH LOW
How do solutions affect cells?
• Water is always moving IN and OUT
• Equilibrium
Isotonic (Solution) Solute concentration inside the cell is equal to the outside cell.
Hypertonic (Solution) Solute concentration outside the cell is higher than the inside cell.
Hypotonic (Solution) Solute concentration outside the cell is lower than the inside cell.
*Normal *Shrinks/shrivels *Swells/bursts
No NET (overall) movement of water (in and out are equal = equilibrium)
Net movement is OUT of cell
Net movement is INTO the cell
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Cytolysis & Plasmolysis
Cytolysis Plasmolysis
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Isotonic Solution
NO NET MOVEMENT OF
H2O (equal amounts entering & leaving)
Hypotonic Solution
BURSTING
Hypertonic Solution
SHRIVELING
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Osmosis in Red Blood Cells
Isotonic Hypotonic Hypertonic copyright cmassengale
Please take out a separate sheet of paper
• Based on the composition of the cell and its environment, we can predict which way water will move.
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Cell in Isotonic Solution
CELL
10% NaCl 90% H2O
10% NaCl 90% H2O
What is the direction of water movement?
The cell is at _______________. equilibrium
ENVIRONMENT
NO NET MOVEMENT
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Cell in Hypotonic Solution
CELL
10% NaCl 90% H2O
20% NaCl 80% H2O
What is the direction of water movement?
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Cell in Hypertonic Solution
CELL
15% NaCl 85% H2O
5% NaCl 95% H2O
What is the direction of water movement?
ENVIRONMENT
• Turn to the page that looks like this
• Movement of molecules across a membrane AGAINST the concentration gradient
• Always LOW HIGH CONCENTRATION • Always requires ENERGY! • Molecules & ions usually require a
protein pump within the membrane • Larger materials require the cell
membrane to change shape • Examples: Calcium, sodium, &
potassium ion transport, Sodium-Potassium Pump, endocytosis, exocytosis
Online Resources • www.pearsonsuccessnet.com • Log in with user name and
password (directions on class website)
• Select “Content” Unit 3 Cells Chapter 7 7.3 Cell Transport (view) Activities
• Art in Motion
LOW HIGH
ATP
Process of taking in liquids or larger molecules INTO a cell by engulfing in a vesicle (requires energy) Includes pinocytosis & phagocytosis
Outside cell Outside cell Outside cell
Inside cell Inside cell Inside cell
Cell membrane
Vesicle
Vesicle breaks down when fused to lysosome
Large molecule
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Moving the “Big Stuff”
Large molecules move materials into the cell by one of three forms of endocytosis.
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Phagocytosis About to Occur
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Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)
Process of releasing materials/substances out of a cell by fusion of a vesicle with the membrane (requires energy)
Inside cell Inside cell Inside cell
Outside cell Outside cell Outside cell
Vesicle to be secreted
Vesicle transported to cell membrane
Contents released outside the cell
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Exocytosis The opposite of endocytosis is exocytosis. Large
molecules that are manufactured in the cell are released through the cell membrane.
Inside Cell Cell environment copyright cmassengale
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Exocytosis Exocytic vesicle immediately after fusion with plasma membrane.
