You should be able to:
•Define osmosis & diffusion.
•Determine why do we need to regulate osmosis.
•Identify what controls osmosis.
•Distinguish between a turgid cell, flaccid cell, and plasmolyzed
cell.
•Define “Iso”, “hypo”, and “hyper”.
•Describe the water move during passive transport
•Know which type of passive transport requires a protein
Diffusion and Osmosis
What is osmosis?
– The diffusion of water across a selectively
permeable membrane
What is diffusion?
- molecules moving from a high to
low
concentration…also called “going down the
concentration gradient.”
Why do we need to regulate osmosis?
– To maintain homeostasis because the
plasma membrane is NATURALLY
permeable to water
How long does water diffuse in a
solution?
-
Until it is evenly distribution, or reaches
equilibrium
What controls osmosis?
– The concentration gradient
What is a concentration gradient?
– The unequal distribution of
particles
Osmosis
Osmosis in
Plant & Bacterial Cells
• Plant cells have turgor pressure. Since they
have a cell wall & central vacuole that stores
extra water, there is water pressure inside a
cell that pushes against the cell wall
depending on how much water is inside the
central vacuole.
Types of Solutions
Remember: Salt Sucks
Isotonic Solution:
•"ISO" means equal
• the concentration of
solute is the same
inside and outside the
cell
Types of Solutions
Hypotonic Solution:
• "HYPO" means less
• the concentration of
solute is higher inside
the cell than outside
the cell
Types of Solution
Hypertonic Solution
• "HYPER" means more
• The concentration of
solute is higher outside
the cell than inside the
cell
•SOLUTE: equal inside &
outside the cell
•WATER: moves in both
directions
•ANIMAL CELLS: stays the
same
•PLANT CELLS: slightly firm
•WHICH CELL LIKES IT BEST:
Animal
Isotonic Solution
•SOLUTE: more inside the cell
•WATER: enters the cell
•ANIMAL CELLS: swells
•PLANT CELLS: very firm
•WHICH CELL LIKES IT BEST:
Plant
Hypotonic
Solutions
•SOLUTE: more outside the cell
•WATER: leaves the cell
•ANIMAL CELLS: shrinks
•PLANT CELLS: wilts
•WHICH CELL LIKES IT BEST:
they both HATE it!!!!!!!
Hypertonic
Solution
Passive Transport:
• Passive Transport –molecules moving from a high to
low concentration & this DOES NOT REQUIRE
ENERGY..also called “going down the concentration
gradient”
• What type of diffusion needs the help of proteins for
materials to move through the membrane?
Facilitated diffusion
Types of Transport Proteins
• Channel Proteins- form channels that allow
specific molecules to flow through.
• Carrier Proteins - change shape to allow a
substance to pass through the plasma
membrane.
Type of
Transport
Diffusion
What’s Happening
Molecules move from high to low
concentrations
Osmosis Water is diffusing (moving from high to
low concentrations)
Facilitated
Diffusion
Molecules move from high to low
concentrations, but they need
proteins to help them