DIFFUSION AND OSMOSIS
3.4 Diffusion and Osmosis
KEY CONCEPT Materials move across membranes
because of concentration differences.
Diffusion and Osmosis
Concentration Gradient: the gradual difference in
the concentration of solutes in a solutes in a
solution between two regions.
3.4 Diffusion and Osmosis
Passive transport does not require energy input from a
cell.
• Molecules can move across the cell membrane
through passive transport.
• There are two types of
passive transport.
• diffusion
• osmosis
3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive
transport.
• Molecules diffuse down a
concentration gradient.
3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive
transport.
• Osmosis is the diffusion of water molecules across a
semipermeable membrane.
3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
• There are three types of solutions.
• isotonic
•
hypertonic
•
hypotonic
Diffusion and Osmosis
In terms of the solution:
Hypertonic: When the solution is more concentrated than
what’s inside the cell. This means water moves out to try
and even out the concentration gradient. (The cell
shrinks..i.e your fingers in the bathtub)
Hypotonic: When the concentration is less concentrated
than what’s inside the cell the water moves in to try and
even out the concentration gradient. (The cell bursts or
“lyses”.)
Isotonic: When the concentration inside the cell is equal to
that outside. No net change in water.
Gizmo
3.4 Diffusion and Osmosis
Some molecules can only diffuse through transport
proteins.
• Some molecules cannot easily diffuse across the cell
membrane.
• Facilitated diffusion is
diffusion through transport
proteins.
Review
Plants Cells vs Animal Cells
Two organelles that are in plants that are not
in animals:
Chloroplasts- which is where photosynthesis
occurs
Cell Wall-Which helps make the plant rigid
and support the change in water pressure.
You will not see these in animal cells.
Lab Report
6 Pieces of Information:
Purpose- raises the question that you sought to
investigate with the experiment
Hypothesis- is a tentative explanation for an
observation. Often written in an “if/then” format.
Lab Report
Materials-List of things needed and used (Needs to
be as precise as possible include dependent and
independent variable, make sure you know or
indicate your control group)
Procedure- Exactly what you did to test your
hypothesis. Use action verbs , perhaps number
the steps
Lab Report
Observations and Data- Anything you measured
during the experiment. (also anything you saw,
touched, felt, smelled or heard)
Data Analysis/Results- Did your test support you
hypothesis. What conclusions can you draw by
looking at the data.