1. Do Now, Agenda Do not sit at a lab table for now
Today: Tonicity Notes, Potato Cell Lab
Cell Membrane Quiz MON 12/5

2. Lab Set Up Get 3 potato slices from teacher.
Make initial observations about potato slices & Measure initial mass of potato slices. Record in data table. (keep track of which ones will go in each cup)
Place potato slices in different cups and obtain salt solutions
Return to seats.

3. Solutions
Cells are surrounded by watery solutions and are filled by watery solutions.
A solution is made up of a solute and a solvent
Solute: the substance being dissolved
Solvent: the substance that dissolves the solute

4. Solutions The concentration of a solute is important to organisms.
Organisms cannot live unless the concentration of dissolved substances stays within a narrow range.
Since many solutes cannot easily move across the cell membrane, the movement of water across the membrane helps to balance the concentrations of dissolved substances (solutes) in a cell

5. Osmosis
The passive transport of the movement of water across a selectively permeable membrane.
Like other molecules, the movement of water is controlled by differences in concentration(a concentration gradient)
Water will move in the direction where there is a high concentration of solute (hence a lower concentration of water)
“Salt Sucks”

6. Tonicity
Tonicity = the measurement of solute concentration on either side of a membrane.
The tonicity of a cell’s environment affects the rate of osmosis (movement of water) across the cell membrane.

7. Hypertonic Solutions
Has a higher solute concentration compared to the cell
When a cell is placed in this type of solution, water will move out of the cell to achieve an equal concentration of solute inside and outside the cell.
This causes the cell to shrink

8. Hypotonic Solutions
Has a lower solute concentration compared to the cell
When a cell is placed in this type of solution, water will move into the cell to achieve an equal concentration of solute inside and outside the cell.
This causes the cell to grow, and sometimes burst

9. Isotonic Solutions
Has a similar solute concentration compared to the cell
When a cell is placed in this type of solution, water will move in & out of the cell equally to achieve an equal concentration of solute inside and outside the cell.
This causes the cell to stay the same size

10. Active vs. Passive Transport
Does not need energy; happens on its own
Substances naturally move from areas of high concentration to low concentration
Osmosis and diffusion are examples of passive transport

11. Active vs. Passive Transport
Active Transport
Requires energy; does not happen on its own
Substances are transported from areas of low concentration to high concentration
The sodium-potassium pump is an example of active transport

12. To complete Finish potato cell lab—turn in
Complete cell membrane transport questions on back of notes—get stamped.