AP Lab 1

Completing the Research Notebook for AP Biology Lab #1.....Diffusion and Osmosis

Resource: Lab One, Diffusion and Osmosis

Page 1 in the AP Biology Lab Manual

Pre-lab: Complete the following parts in your research notebook prior to conducting the laboratory.

Part 1: Title

Do not develop a title until your have completed the pre-lab. Then, develop a title for this laboratory

that is in the form of a question.

Part 2: Objectives (What are the objectives for this laboratory?)

Part 3: Pre-lab Questions

Activities A and B

1. Why is the cell membrane said to be “semipermeable”?

2. Differentiate “active transport” and “passive transport”.

3. Explain the concept of diffusion. Use an example in your explanation.

4. Define osmosis. Use blood cells to explain the terms isotonic, hypertonic and hypotonic, in terms

of comparing solutions on either side of a semipermeable membrane.

Activity C S-8

5. Why is the concept of water potential used?

6. In plant cells, what two factors are important in determining the direction of water across the

membrane? Why?

7. Why does the water potential decrease when a solute is dissolved in water?

8. What is a rule for the “net movement of water”?

9. Situation: A potato cell is placed in pure water.

Assigning a value for solute potential as -9 bar, explain whether or not water will diffuse into the cell,

using the formula for water potential.

10. Situation: A potato cell is placed in a cup of water that has solute dissolved (-15 bar). Explain

what will happen to the cell, why, and the term for this.

11. What formula is used for calculating solute potential? (identify i, C, R, T)

Part 4: Methods (Read the procedures carefully for each activity. You may write the following

Method A:

A simulated cell made of dialysis tubing containing a glucose/starch solution will be placed in water

containing IKI (iodine) solution.

Method B:

The influence of solute concentration on the net movement of water molecules through a

semipermeable membrane will be investigated. 25 mL of the following sucrose solutions will be

placed in dialysis bags: 0.0 M (distilled water), 0.2 M, 0.4 M, 0.6 M, 0.8 M , 1.0 M. The dialysis bags

will be submerged in distilled water for 30 minutes. The % change in mass of bags will be

determined:

Hypothesis_____________________________________________________________________

Method C

The concept of water potential will be investigated by immersing potato cores in varying sucrose

solutions and determining % change in mass of the cores over a 24-hour time period. A graph will be

constructed to determine the molarity of the potato cores. A value for solute potential will be

calculated using the molarity of the potato cores from the graph.

Method D:

Plasmolysis will be observed in onion cells after a salt solution is applied to a wet mount of onion

cells.

Part 5: Preparation of Data Tables

Page 2 Table 1.1 Title of table: Activity A: Diffusion

Page 5 Table 1.2 Title of table: Activity B: Osmosis

Note: add a column that is called “Percent Change in Mass-Class Average”

Page 11 Table 1.4 Title of Table: Activity C: Water Potential and Potato Cells

Activity D Draw a 5X5 cm box and label “Before Salt Water added” and a 5X5 cm box labeled “After

After conducting the laboratory: Post-lab work in research notebook:

Post-lab for Diffusion and Osmosis

Analysis of Results

Do by Part

Part A Page 3, # 1-3

Part B Page 7, #1-5

Part C Page 14, # 1-10

Part D Page 18, # 1-3

Part 7: Graphs

Label Title of each graph

Label All axes

Label "Independent, Dependent"

Must be at least 1/2 page.

Part B

Dependent Y = % change in mass

Independent X = M of sucrose

Part 8: Theme Correlation

How has this lab illustrated the theme of structure and function?

How has this lab illustrated the theme of inquiry in science? (hypothesizing, control, etc.)

Part 9: Conclusion Topics

1. Diffusion-explain it, and use your data to show you demonstrated this process.

2. Osmosis-explain it, and and use your data to show you demonstrated it.

How was inquiry used to show concepts in part B.

3. Water Potential-explain it, use your data to show you demonstrated it.

How was inquiry used to find solute potential and water potential of potato

cells at equilibrium.?