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Diffusion, Membranes, and Cryogenics: Can We Freeze Cells? (page 2)

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Author: Stephanie, Grade 8

Hypothesis

What Will Pass Through a Membrane?

I expect to see the glucose go through the membrane and the starch not being able to because a starch molecule is too big. The glucose molecule is a simple sugar and a rather small molecule. It should be able to fit through the membrane easily.

Freezing Cells

I expect to see the salt preserving the beets when they are frozen because the salt will help the water in the beet cell (some of it) to diffuse out. This will leave enough room for the water in the cell to expand and still fit in the cell.

Materials

 

What Will Pass Through a Membrane? Freezing Cells:

*Glucose

*Benedict's solution with dropper

*Iodine with dropper

*Starch

*tablespoon

*about 30 test tubes

*beakers (6 or 7)

*tongs

*heating surface

*goggles

*rubber bands and/or tape

*membrane

*graduated cylinder (10ml.)

*test tube rack

*labels

*camera

*Beets (1 or 2 small ones)

*sharp knife

*salt (large container)

*18 baby food jars (or at least jars around that size)

*spectrophotometer (colorimeter)

*a scale that weighs grams

*a ruler

Procedure

 

What Will Pass Through a Membrane? Freezing Cells

1. Make a scale of different colors made when .1%, .09%, .08%, .07%, .06%, .05%, .04%, .03%, .02%, of glucose is added to Benedict's Solution and put in a hot water bath for 5 minutes.

2. Label the jars (test tubes) and take pictures.

3. Place 5 ml. of .1% glucose into two test tubes.

4. Place 10 ml. of .1% glucose into two different test tubes.

5. Place a piece of membrane over the top of each test tube and make sure to "seal" the sides of the membrane with tape and/or rubber bands.

6. Place each test tube into a beaker (upside down) filled with 50 ml. of water.

7. Place 5 ml. of water into a test tube with a tablespoon of starch. (Do this twice to ensure accuracy.)

8. Place a piece of membrane over the top of each test tube and make sure to seal the sides of the membrane with tape and/or rubber bands.

9. Place each test tube into a beaker (upside down) filled with 50 ml. of water.

10. Wait overnight and put 5 drops of Benedict's Solution in each test tube that the glucose is in.

11. Place each in a hot water bath and compare how much extra water diffused up with the pictures taken.

12. Put 5 drops of Iodine in each starch beaker, then place them in a hot water bath for 5 minutes. If the color changes darker, then the starch passed through the membrane.

1. Use the ruler to cut out 12- 1 cm3 sized beet sections.

2. Weigh the beets, and make sure that all of them weight the same size. (14 grams.)

3. Fill 3 jars with plain tap water.

4. Fill another three jars with 10% salt content in 50 ml. of water.

5. Fill another three jars with 20% salt content in 50 ml. of water.

6. Fill another three jars with 30% salt content in 50 ml. of water.

7. Fill another three jars with 40% salt content in 50 ml. of water.

8. Fill the last three jars with 50% salt content in 50 ml. of water.

9. Split the jars into three sets each having 0%, 10%, 20%, 30%, 40%, and 50% salt content in 50 ml. of water.

10. Place a beet cube in each of the jars of 2 of the sets. Leave the third set empty!

11. Place one of the sets with beets in it in the freezer. Place the other two sets in the refrigerator.

12. After a day or two, take all of the beet jars out.

13. Use the spectrophotometer to measure the Absorption and Transmittance percentage for each of the beet jars. Use the light setting 530 nm. Use the set of jars with no beets in them as the blank samples (control).

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