| Cube Size | Total cube volume (cm3) | Total volume that was not pink (cm3) | Volume of the diffused cube (total – volume not pink) | Percent diffusion | Surface area of cube (cm2) | Surface area to volume ratio |
| 1 cm | 1 cm3 | 0.25 cm3 | 0.75 cm3 | 75% | 6 cm2 | 6:1 |
| 2 cm | 8 cm3 | 4.4 cm3 | 3.7 cm3 | 46% | 24 cm2 | 3:1 |
| 3 cm | 19.8cm3
(3x3x2.2) |
9.9 cm3 | 9.9 cm3 | 50% | 44 cm2 | 22:9.9 |
Conclusion Questions:
- In terms of maximizing diffusion, what was the most effective size cube that you tested?
The 1 cm cube was the most effective at diffusion. It had a 75% diffusion. It also had the biggest difference between surface area and volume in the ratio 6:1.
- Why was that size most effective at maximizing diffusion? What are the important factors that affect how materials diffuse into cells?
This size was most effective because it had the highest surface area to volume ratio. It has the least amount of volume to be able to get to the middle and more surface area to diffuse through, compared to its size. Important factors include surface area, volume, and also things like temperature and the concentration.
- If a large surface area is helpful to cells, why do cells not grow to be very large?
When cells grow, their volume increases at a greater rate than surface area, therefore decreasing the SA:V ratio. This would make diffusion less effective, so it’s better to keep the cells small.
- You have three cubes: A, B, and C. They have surface to volume ratios of 3:1, 5:2, and 4:1 respectively. Which of these cubes is going to be the most effective at maximizing diffusion, how do you know this?
The 4:1 cube is going to be the most effective at maximizing diffusion because it has the highest SA:V ratio. The cube has more area of contact for diffusion and less volume to have to move through to get to the middle, making it the most effective.
- How does your body adapt surface area-to-volume ratios to help exchange gases?
The body shapes cells into longer, thinner shapes to reduce the volume and increase the SA and can also fold the surface of the object or cell membrane to create more surface area. The body has also evolved things like the gas exchange organs (the lungs) and circulatory system (the blood) to speed up the movement of materials.
- Why can’t certain cells, like bacteria, get to be the size of a small fish?
Bacteria is very small, so it has a high SA:V ratio. However, when the cell starts to grow, this ratio starts to lower. When the unicellular organism gets too big, it stops growing and divides in order to keep the high ratio and adequate diffusion level.
- What are the advantages of large organisms being multicellular?
The advantages of large organisms being multicellular includes the body having a greater diffusion rate, as many small cells have a higher ratio than one big cell does. Cells rely on diffusion to get the important substances they need in and out of the cells. When a cell is smaller, it takes less diffusion to get the substances to the middle of the cells. Multicellular organisms can also perform more functions than a unicellular organism being it has more cells able to do jobs. As well, a multicellular organism would live longer as there is less stress on each cell.