Agar Cube Lab: Cell Size & Diffusion

Background

Cells depend on diffusion to exchange materials with their environment. The efficiency of diffusion is influenced by cell size and its surface-area-to-volume (SA:V) ratio. In this lab, you will use agar cubes prepared with phenolphthalein indicator and sodium hydroxide (NaOH) as model cells to investigate how diffusion works and why cells tend to be small.

What Happens at Each Step:

1. Step 1 (Prediction): Formulate and write your hypothesis in your lab notebook before starting.
2. Step 2 (Table Setup): Draw the model data table into your notebook to track measurements and calculations.
3. Step 3 (Initial Measurements): Measure the side length of each cube using the metric ruler and calculate SA, Volume, and SA:V ratio.
4. Step 4 (Vinegar Submersion): Drag all three cubes into the 200 mL beaker of vinegar for a 10-minute reaction period.
5. Step 5 (Slicing & Analysis): Observe the cross-sections of the vertically sliced cubes, measure diffusion depth with the ruler, and estimate the percentage of the cube diffused.