Notes 5.1
Osmosis in Action
Pages 99-100
Table Talk
•Watch
this video.
•As a group discuss the answers to these
questions:
•
•
•
What organism is this?
What kind of environment do you think it’s in?
What is happening?
Standards
•CLE 3210.1.5 - Compare different models to
explain the movement of materials into and out of
the cell.
SPI 3210.1.8 - Compare active and passive
transport.
RLE 2010.2.1 - Recognize the importance of
homeostasis as a survival mechanism.
•
•
Objectives
1.Compare different models to explain the
movement of materials into and out of the
cell and the role of the solution the cells
exist within.
•
•
•
Diffusion
Facilitated diffusion
osmosis
2.Recognize the importance of homeostasis
as a survival mechanism.
Quick Review
•Solutions
•
•
have:
Solvent: The liquid that dissolves the solute.
Solute(s): The substance that gets dissolved.
•Concentration:
the amount of a substance in a given volume
•Osmosis:
When water moves
from high to low
concentration.
So What?
•Cells
live in solutions…. So we’ve named
the three types of solutions:
•
•
•
Isotonic
Hypertonic
Hypotonic
Isotonic
•Isotonic:
Concentrations of solutes are the same inside and outside of
the cell.
•What
happens:
Water is at an equilibrium so it
moves freely into and out of the cell
at the same rate.
Hypertonic
•Hypertonic
Concentrations of solutes are higher outside the cell than
inside.
•What
happens?
Water moves outside the cell in order to
create a dynamic equilibrium. Cells shrivel
up and may die (in plants it’s called
plasmolysis.)
Hypotonic
Hypotonic:
Concentrations of solutes are lower outside the cell than
inside.
What happens:
Water moves into the cell in order to create a
dynamic equilibrium. Cells expand and may
explode (called cytolysis.)
Summary
Good graphic on page 99.
Review
•Watch
this video again.
•As a group discuss the answers to these
questions:
•
•
•
What organism is this?
What kind of environment do you think it’s in?
What is happening?
Quick Review
Equal
•Isotonic – solutes are __________
within the solution in comparison to the
cell
Higher
•Hypertonic – solutes are __________
within the solution in comparison to the
cell
Lower
•Hypotonic – solutes are ___________
within the solution in comparison to the
cell
Objectives
1.Compare different models to explain the
movement of materials into and out of the
cell and the role of the solution the cells
exist within.
•
•
•
Diffusion
Facilitated diffusion
osmosis
2.Recognize the importance of homeostasis
as a survival mechanism.
Cell Responses to Osmosis
Land Organisms:
Cells inside our bodies are in slightly hypotonic environments.
Saltwater Organisms:
No problems under normal conditions.
Freshwater organisms:
Live in a hypotonic environment.
Hypotonic Environment
Defenses
Single-cell organisms:
Contractile Vacuole:
a sac that stores water and when it is full the sac contracts
and the water is expelled. (If it fails the paramecium will die.)
Multi-celled organisms:
Solute Pumps:
Proteins in the cell membrane can pump solutes out of the
cell, making the concentrations of water more equal.
Plant Cells
Hypotonic Environments:
Turgor Pressure
As the plant cell swells, the pressure of the water is not
enough to break the cell wall. This gives soft plants rigidity.
Hypertonic Environments:
Plasmolysis
As plant cells lose water, the cell membrane pulls away from
the cell wall and turgor pressure is lost and the plant wilts.
No Defenses
Some cells have no defense against
osmosis.
Example:
Red Blood Cells - hypotonic
Red Blood Cells - hypertonic
Review
•Watch
this video again.
•As a group discuss the answers to these
questions:
•
•
•
What organism is this?
What kind of environment do you think it’s in?
What is happening?
Review the Objectives
1.Compare different models to explain the
movement of materials into and out of the
cell and the role of the solution the cells
exist within.
•
•
•
Diffusion
Facilitated diffusion
osmosis
2.Recognize the importance of homeostasis
as a survival mechanism.