In our diffusion in agar cubes lab, three different sized agar cubes were used to test which size was the most effective at maximizing diffusion.

 

The 1cm size cube is the most effective at maximizing diffusion because it had the greatest surface area to volume ratio (6:1). As the cube size increases, the surface area to volume ratio decreases and there is less material for the NaOH to diffuse through causing the NaOH longer to get to the middle of the agar cube. This is the reason why cells do not grow to a large size as even though the surface area is greater, it is not enough to compensate for the increased volume of the cell so the cell does not get the required nutrients it needs. Therefore when a cell becomes too big, it is forced to divide to keep a high surface area to volume ratio. This is why a cell does not grow to the size of a fish. In multicellular organisms, each cell has a large surface area to volume ratio but they have features like gas exchange organs and circulatory systems to speed up and help the transport of materials in and out of the organism. In our body, we need a high surface area to volume ratio to effectively exchange gases. Some factors that affect materials diffusing into our tissues or cells are membrane thickness, temperature, pressure, surface area, and the difference in concentration on both sides. In an example, cube A has a surface to volume ratio of 3:1, cube B has a ratio of 5:2, and cube C has a ratio of 4:1. In this example, cube C is the most effective at maximizing diffusion due to it having the highest surface area to volume ratio.