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

After leaving our cubes in the sodium hydroxide solution for 10 minutes, and then cutting them open: it became clear that the smallest cube was the only cube that was fully pink, and therefore would be the most effective at diffusion.

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 had the greatest surface area to volume and therefore was the most effective sized-cube for maximizing diffusion. The idea of having a greater surface area (to volume) ratio, means that the solution can fully surround the cube and enter/diffuse through more of the volume as it is coming in through the surface area aspect (greater surface area to volume ratio, more solution is able to diffuse into “insides” of cube). Other important factors that could affect how materials diffuse into cells/tissues could be the concentration/pressure/temperature/nature of material/thickness/surface area:volume. All of said factors can cause the diffusion (rate and effectiveness) to be altered, although the greatest impact we saw in the lab was the surface area: volume ratio.

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

As seen in the lab, surface area was incredibly helpful in increasing the effectiveness of diffusion, and it also is very useful in regards to allowing nutrients/resources/wastes/energy/etc. pass through the cell membrane.  However, a larger size, while increases the surface area, also increasing the volume: and in fact, results in a smaller surface area: volume ratio. This means that in reality, diffusion becomes harder (and other nutrients/functions/”uses” of surface area as well) and less effective. In the end, a small size creates a larger and more effective surface area: volume ratio and means that the cell will over all function (and diffuse) better.

 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 most effective cube is cube C, with the 4:1 ratio being the largest one (meaning the surface area: volume ratio is greater and will allow diffusion to be most effective). The less “volume” in the surface area:volume ratio, the less material that materials have to pass/go through in order to travel in/out of cells.  The greater the volume of a cell or cube (in this case), the more area that the outside source will have to penetrate in order to fully diffuse: the less area, the faster and easier it can/will fully diffuse.

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

Your body can adapt it’s ratios in a number of ways. When a cell gets too large, they will divide (in our bodies) in order to maintain the best possible surface area:volume ratio. Most of the organelles in cells, and in intestines, will have folds in their membranes as well. Some of our cells are shaped differently in order to maximize diffusion (and best exchange gases as well): for example, our nerve cells are are thin and long. While our cells have many great examples of our adaptations in order to maintain our most effective surface area:volume ratios, our bodies themselves have other factors (like our lungs, or systems) that help maximize diffusion in our bodies in general.

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

As previously mentioned, once cells start to grow, their large surface area: volume ratios start to become smaller, and less efficient. The cell or bacteria will start to function less efficiently as their diffusion capabilities/efficiency diminishes. Therefore, the cell or bacteria will divide in order to prevent this loss of functionality/efficiency and should not normally/naturally reach the size of a fish.

What are the advantages of large organisms being multicellular?

One of the greatest advantages of large organisms being multicellular is that their rate of diffusion is higher (necessary as there are can be a greater number of functions/specialized systems in large organisms). Their higher rate of diffusion allows for a greater efficiency and functionality as an organism, and of the organism’s processes and systems. This allows for their more specialized systems and capacities and even their overall function as an organism to achieve a higher state of effectiveness/efficiency.