Diffusion, Membranes, and Cryogenics: Can We Freeze Cells? (page 3)

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Author: Stephanie, Grade 8


Feezing Cells: Effect of Salt Concentration on Cell Damage

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What Will Pass Through a Membrane?

The data in this project tells us where a rough boundary line is of how big a molecule can be and still be able to diffuse through a membrane. This could help us understand why digestion is so important and takes so long to actually happen. This could also tell us what kinds of things you could actually have in your cells.

Freezing Cells

The data for this project tells us how much salt is needed for the preservation of cells after freezing them. Damaged cells release their pigment into the water, thus decreasing light transmission. 0% salt solution after freezing resulted in 0% light transmission, showing almost complete cell damage. In a 20% salt solution, the preservation rate increased dramatically, indicated by an increase in light transmission. At 40% salt content, most cells seem to have been prevented from rupturing. The refrigerator data acts as a control and shows little cell damage, indicted by high light transmission. There was a drop in light transmission at 40% salt and above. I do not have an explanation for this.

The data also tells us that it might be possible to freeze cells and bring them back to life afterwards. This is one of the first steps in the preservation of animals.


What Will Pass Through a Membrane?

My hypothesis that a starch molecule would be too large to go through a membrane was correct. I was also correct that glucose was able to diffuse. This project proves that even though both starches and sugars are carbohydrates, they are different in size. Starch molecules are too complex to diffuse through a membrane. The project proves that not all molecules can pass through a membrane.

This information helps us understand the process of digestion. The food molecules have to be digested to a certain size for the cell to "accept" it.

Freezing Cells 

My hypothesis, that the salt would preserve frozen beet cells, was correct. The jars with the most salt in the freezer were only affected by the freezing a little bit, while the jars with little salt were bright purple from dead cells.

This project proves that there is a way to save cells and preserve them. This also proves that one day people might be able to freeze animals and then bring them back to life. The significance of these findings is that if later in the history of the world, people could be frozen, then brought back to life so many years later, they would be able to tell much about history.

My recommendations for future study is to use a variety of cells and try preservation on as many as you possibly can; it may help history! Another recommendation would be to do further tests to see if the frozen cells actually survive after thawing. Also one could use different types of preservation to see what works the best.


Starr, C., Biology: Concepts and Applications, Belmont, CA, 1991, pp. 27 - 29, 40 - 43.

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