Activating Prior Knowledge
• Egg Osmosis
• What is an egg?
• Soak a chicken egg in
vinegar to
• A chicken egg to be
– Remove the cell, and
more precise…
– Denature the outer protein
• Then you have a big cell
to experiment with!
• View and Interpret
Egg Osmosis Video
After this lesson,
you should be able to
• explain the impact of water on life processes (i.e.,
osmosis, diffusion, SB1d).
• explain the role of the cell membrane, in maintaining
homeostasis (transporting materials in/out of cell).
• Use vocabulary:
– hypertonic, hypotonic, isotonic
– Passive Transport: diffusion, osmosis, facilitated diffusion
– Active Transport: sodium/potassium pump and
endo/exocytosis
Solution Review
• Solvent – the larger
• Solution – Complete
material {liquid} that
mixture of solute and solvent
dissolves the solute
• Ex. Sweet tea
• Water is considered the
“universal” solvent
• Solute – smaller
substance that is
dissolved by the solvent.
Ex. tea & sugar
Quick Check!
I mixed Kool-Aid powder in
water. Describe the mixture
using the terms:
solute, solvent, and solution.
Words to know:
Hypertonic
More solute
Hyper means higher
{more concentrated}
Hypotonic
Less solute
Hypo means lower
less concentrated
Isotonic
Solution has
achieved
equilibrium
Equilibrium
achieving
balance or equal
Diffusion Demonstration
• Equal volume of cold and
warm water, each in
separate clear cups
• What will happen if we
drop equal amounts of
food coloring in each?
• Let’s try it and observe.
• youtube
• Explain what you see.
• Lead discussion to develop
diffusion definition including
–
–
–
–
–
Movement of a substance
Random molecular motion
Kinetic energy
Concentration gradient
equilibrium
Diffusion
• Movement of substances
from high concentration to
low concentration
• Movement “down a
concentration gradient”
• Due in part to random,
rapid motion of molecules.
•
•
•
•
•
Net Movement
Equilibrium State
Simple Diffusion.
Roles in the Body
Factors that Affect Rate:
– permeability of membrane
– Size of gradient
– temperature
Passive Transport
• Movement of
materials in & out of
the cell without {NO}
Energy
Hypertonic
High
Hypertonic
Low
hypotonic
Hypotonic
Diffusion
• Passive
• O2, CO2, H2O across
cell membrane
• Smells spreading
• Movement of any
molecules from a high
concentration to a low
concentration.
Osmosis
Diffusion of water
across a semipermeable
membrane
Osmosis
• Diffusion of water through
a selectively permeable
membrane.
• Movement of water
– from “less salty” to “more
salty” side of membrane
– from low solute
concentration to high solute
concentration.
– from high water
concentration to low water
concentration.
•
•
•
•
Hypertonic
Hypotonic
Isotonic
In everyday life:
– Preservation of food
– Eating of salty or sugary
foods
– Salt on a slug
– contractile vacuoles
– turgur pressure in plants
Diffusion and Osmosis Experiment
Initial
Contents
Dialysis
Tubing or
Plastic Bag
Beaker or
Clear Cup
Initial
Solution
Color
Final
Solution
Color
Initial
Presence of
Glucose
Final
Presence of
Glucose
OSMOSIS DEMONSTRATION
(DIALYSIS BAGS)
Interpret this experiment!
OSMOSIS IN PLANT CELLS
What’s happening to the water in the cell?
HYPOTONIC SOLUTION=
NORMAL TURGOR
PRESSURE
HYPERTONIC
SOLUTION=
PLASMOLYSIS
OSMOSIS IN PLANT CELLS
(Elodea)
Plasmolyzed cells
Solution Concentrations
• Isotonic Solution
– When a cell is in a solution that has the same
concentration of water and solutes
• Hypotonic Solution
– A cell is in a solution that has a lower concentration of
solute
• Hypertonic Solution
– A cell is in a solution that has a higher concentration
of solute outside of the cell
Quick Check
Knowing what we know about osmosis,
what would happen to the water in a cell
in:
1. an isotonic solution?
2. a hypotonic solution?
3. a hypertonic solution?
Osmosis
• Passive
• Hyper to Hypo
• Diffusion of water
molecules across a
membrane.
• Net movement of
water toward high
solute (hypertonic)
side of membrane
Osmosis and Animal Cells
NO CHANGE
CRENATION
WILL LYSE
Facilitated Diffusion
• Passive
• Diffusion that uses
channel proteins
• Hyper to Hypo
• Large molecules like
glucose
Facilitated Diffusion
• Movement from high
concentration to low
concentration through
carrier proteins.
• Used to move ionic or
large substances into
or out of cells
• Passive process
• Carrier proteins are
specific (will only
move one substance)
• Important for moving
sugars and amino
acids into cells
Active Transport Low to High
• Movement of
materials in &
out cell WITH
energy
High
Lo
w
Quick Check!
What is the main
difference between active
and passive transport?
Ion or Solute pump
• Active
• Protein channel
• hypotonic to
hypertonic
• Ex. Na+ K + pump
• To “pump” means it
uses energy (ATP)
Active Transport
• Movement of substances
against a concentration
gradient.
– From low concentration to
high concentration.
• requires energy
• pumping a substance
• ATP must be hydrolyzed
to fuel this process
• Sodium-Potassium Pump
• Pumps sodium out of cells
and potassium into cells.
• Important for the
functioning of nerves and
muscles.
• Pump is a membrane
protein and an enzyme-ATPase.
Sodium-Potassium Pump
(this allows for nerve function!)
3 Na+ pumped in for every 2 K+ pumped
out; creates a membrane potential
Moving the “Big Stuff”
Exocytosis
- moving
things
out.
Molecules are moved out of the cell by vesicles that fuse
with the plasma membrane.
This is how many hormones are secreted and how nerve
cells communicate with one another.
Pinocytosis
• Cell forms an
invagination
• Materials dissolve
in water to be
brought into cell
• Called “Cell
Drinking”
Endocytosis – Phagocytosis
Used to engulf large particles such as
food, bacteria, etc. into vesicles
Called “Cell Eating”
Three Forms of Transport Across the Membrane
Cellular Transport
On-Line Tutorial
(11 slides with animated molecules moving across cell
membrane; includes quiz questions along the way)
• ANOTHER ONLINE
TUTORIAL
Closing Challenge – Create a
“Cell Transport Concept Map” with these words:
Active Transport
ATP
Cell Transport
Concentration Gradient
Diffusion
Endocytosis
Exocytosis
Facilitated Diffusion
Passive Transport
Osmosis
O2, CO2, H2O
glucose
Na+ & K+ ions