Question

Data Collection, Statistical Analysis, Cell Size vs. Diffusion Experiment B: The Effect of Cell Size on Diffusion Rate Table 2.3: Agar Cubès Surface Area/Volume Ratio Volume (cm) Surface Area (cm2) Cube Size (cm) 1 2 210? 3 Table 2.4: Rate of Diffusion Elapsed Time (min) Rate of Diffusion Depth of Diffusion (cm) (cm/min) Cube Size (cm) 2 Table 2.5: Extent of Diffusion Volume of Cube which has NOT Changed Color (cm2) % Volume of Cube which has Changed Color Volume of Cube (cm3) Length of Pink Area (Extent of Diffusion) (same as in Table 2.3) QUESTIONS CONTINUED.... 2. Using the graph paper provided construct a graph, showing the relationship between cube volume (cm3) and the extent of diffusion (Table 2.5). 3. Explain why the diffusion of the Diffusion Medium into the agar cube causes the observed color change. 4. If each cube represented a living cell and the Diffusion Medium is a substance needed to survive, what problem might exist for the largest cell? Data Collection, Statistical Analysis, Cell Size vs. Diffusion Procedures: 1. Each team will obtain a 3cm x 3cm x 6cm agar block that has been treated with a base and the pH indicator phenylphthalein (pink in the presence of base, colorless in acid). 2. Using a plastic knife, trim this piece into 3 cubes. One 3cm x 3cm x 3cm; the second- 2cm x 2cm x 2cm; and the third 1cm x 1cm x 1cm. Start with the largest cube first! 3. Calculate the surface area to volume ratio for each cube. Surface Area length x width x # sides Volume length x width x height 4. Place the 3 cubes carefully into a plastic cup. Add the Diffusion Medium until cubes are covered. Keep the cubes submerged for 10 minutes, turning them frequently with the spoon. Be careful not to scratch any surface of the cubes. 5. After ten minutes use a spoon to remove the agar cubes and carefully blot them dry on a paper towel. Do not allow diffusion to continue! Note the exact time of diffusion. 6. Cut the cubes in half, rinsing and drying the knife between each cut. Note the color change from red to pink to clear. This indicates the depth of diffusion of the "Diffusion Medium" into the cubes. 7. Using a metric ruler, measure the distance of diffusion in centimeters (cm) on 1 side. Do this immediately upon removal of the block from the Diffusion Medium! Calculate rate of diffusion for each cube as centimeters per min (cm/min) 8. Calculate the volume of the portion of each cube which has not changed color by first measuring the length of the pink area in the center of the cube and using the formula below: Volume of cube not changed (length pink area) 9. Calculate the extent of diffusion into each cube as percentage of total volume using the formula below: = (Total cube volume - volume of cube not changed) X 100 Total cube volume Extent of Diffusion Student Cleanup Dispose of agar cubes in the trash can Diffusion solution (2 % Acetic Acid) may be disposed of in the sink Return all lab supplies to the appropriate station Clean up your individual lab station Push chairs in to clear all walkways and exits

Answer 1

Answer 1:)

We will get a logarithmic graph because as the time increases more acetic acid will diffuse in the agar cubes containing a dye, however, after some time, the diffusion rate will increase slowly and reach to a definite scale. This suggests that as we increase the duration, the diffusion rate will also increase but it tries to reach equal concentration on both sides and after reaching that point, the diffusion stops.

Answer 2:)

The diffusion takes out the dye color because acetic acid works as the decolorizing agent for the dye. As the acetic acid moves in the cubes, more dyes removed and leaves no color behind.

Answer 3:)

If such diffusion occurs in a living cell, the cell will get an adequte amount of diffusion medium. However, due to slow diffusion, cells evolve some mechanism to increase the entrance of diffusion medium. It is becasue a slow rate will take more time to get diffused and until to get fully diffused, cells may die.

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