Diffusion Cube Argument - Raquel and Sana

Research Question:

Why are cells so small?

Claim:

Cells that have a larger surface area to volume ratio are more efficient at diffusing essential nutrients.

Evidence:

Cubes	Volume (cm3)	Surface Area (cm2)	SA:V ratio	Rate of Diffusion	% Cell Receiving Nutrients
1 (1cm x1cm x1cm)	1	6	6:1	.5cm/20mins	100
2 (1.5cm x1.5cm x1.5cm)	3.4	9	2.6:1	.4cm/20mins	93.6
3 (2cm x2cm x2cm)	8	12	1.5:1	.4cm/20mins	78.4

Justification:

Based on the evidence it proves that the largest surface area to volume ratio was the most efficient at diffusing the vinegar. The smallest cube (cube 1) had the largest surface area to volume ratio which was 6:1. After the 20 minute trial, the cube was completely clear and had 100% diffusion. Cubes 2 and 3 had smaller ratios and were not completely clear after the 20 minute trial. They only diffused 93.6% for cube 2 and 78.4% for cube 3. This means that cube 1 was more efficient at diffusing because it diffused the most amount of vinegar in the same amount of time compared to cubes 2 and 3. This can be related to its higher surface area to volume ratio because cube 2, which had a slightly larger ratio than cube 3, was able to diffuse more than cube 3.

Alternative Claim:

The rate of diffusion is related to cell size.  Nutrients diffuse at a faster rate through small cells than they do through large cells.

Challenge:

Based on the evidence it shows that the rate of diffusion for all three cubes showed no significant difference. Cube 1’s rate was .5cm/20s, Cube 2’s rate was .4/20s, and Cube 3’s rate was .4/20s. The rates were within one centimeter of each other. This disproves the claim because the rates were relatively the same for all three cubes despite their differences in dimension, therefore concluding that diffusion is not related to cell size. Nutrients were diffusing at similar rates to one another no matter what cube size they were.