What determines the efficiency of diffusion throughout the model “cells”?

Hypothesis

As the substance diffuses further inwards, more work will be required. The substance diffuses quickly near the surface but the further inwards it needs to go, the slower the process will be. This means that smaller cells will be more efficient. The percent diffusion of a small cell will be higher than the percentage of a large cell. In a small cell, the substance will have to travel a smaller distance in order to completely diffuse within the cube.

 

Data Table 

Questions 

1) In terms of maximizing diffusion, what was the most effective size cube that you tested?

• The most effective size cube was the 1cm cube with a percent diffusion of 75%.  As we can see from our data as well as photos, the amount of space that was left untouched by the NaOH (as indicated by the lack of pink colouring) in the small cube, is much less in comparison to the two other bigger cubes.

2)Why was that size most effective at maximizing diffusion? What are the important factors that affect how materials diffuse into cells or tissues

• The smallest cube has a lot more surface area than it does volume. This allows for the NaOH to diffuse more effectively into the cube. The increase of surface area, provides lots of space for the NaOH to penetrate the cube.  The low volume of the cube means that the NaOH doesn’t have to penetrate as deep into the cube. In conclusion, surface area and volume are important factors in how materials diffuse into cells or tissues.

3)If a large surface area is helpful to cells, why do cells not grow to be very large?

• It’s true that if cells were to grow to be very large, they would have a large surface area. However, in order for efficient diffusion to occur, a large surface area and a low volume must be characteristics of the cell. It is not the amount of surface area that matters, it is the ratio of surface area to volume. A bigger cube would have a large surface area, however the volume would be increased as well, thus making the ratio less ideal. Therefore, cells remain small in order to be more efficient.

4)You have three cubes, A, B, and C. They have surface to volume ratios 3:1, 5:2, 4:1 respectively. Which of these cubes is going to be the most effective at maximizing diffusion, how do you know this?

• Cube C would be the most effective at maximizing diffusion. Cube C, much like the 1cm Agar Cube used in the lab, has a large surface area and low volume and in turn has the highest ratio of surface area to volume. Since it has the highest ratio, it will be the most effective.

5)How does your body adapt surface area-to-volume ratios to help exchange gases?

• In our respiratory system, we have tiny balloon-like structures known as alveoli. The alveoli are responsible for moving oxygen and carbon dioxide in and out of our blood stream. They accomplish this task through diffusion. In order for this process to be done quickly and efficiently, they have adapted to have a large surface area and low volume.

6)Why can’t certain cells, like bacteria, get to be the size of small fish?

Bacteria are made of only one cell. As we have observed in this lab, in order for efficient diffusion to occur, there must be a large surface area and low volume. If bacteria were to get to the size of a small fish, that would mean the cell would be that large. A large cell of that size would not support efficient diffusion, thus greatly hindering the cell’s ability to function and survive.

7)What are the advantages of large organisms being multicellular?

For single-cell organisms, the size of their cell determines their overall size. As we have learned, a cell must maintain a large surface area and low volume to function effectively enough to survive. However, large organisms are made of lots and lots of cells. Despite the organism being of a large size, the cells themselves remain small enough to maintain the correct ratio to function and maintain life. It’s also worth noting that by having many different cells,  a large variety of functions can be performed simultaneously. This allows for the multi-cellular organism to have more capabilities than a single-cell organism.