Cell Experiments

Cells are small, but not too small for us to experiment with.

Part 1: Cell So Small

Why do cells need to be so small?

In this lab we will model the ability of small vs. large cells to take up nutrients.

Follow instructions on pages C-55 to C-57 of Micro-Life to do "Cell So Small" lab.

Write your responses to 1-5 in your journal:

1. In this lab, what did each of the items represent? HINT: The answers are in your procedure.

a. carbon pieces: __________________

b. carbon powder: _________________

c. blue dye: ______________________

2. What color was the water that flowed out from the carbon pieces?

3. What color was the water that flowed out from the carbon powder?

4. Where does the dye “go” in the vial with the carbon powder?

5. Based on this experiment, WHY ARE CELLS SO SMALL?

Part 2: Cell Membrane

Read and observe the diagram on p. C-51 of the Micro-Life Book. We are going to do an experiment about the function of a cell membrane.

Follow steps 1-8 on p. C-52-C-53 of the Micro-Life Book (note: mix cornstarch and water in the bag, not the cup).

• At step 8, in your journal make this table and complete the "Initial" column. Label the parts of your model where Lugol's/iodine and cornstarch are.

• Set your properly labeled cups (cup #, period #, table #) in the bin at the front of the class and neatly re-organize your bin.

Day 2 Instructions:

• Teacher does procedure step 9 to show when iodine and corn starch mix.

• Observe your cups and do the "Final" column (label cornstarch and iodine).

• Then, in the table in your journal, label the parts of the models that represent:

  • Cell membrane, Cytoplasm, and Environment outside of the cell

• Then, answer these questions in your journal.

• 1. Which particles - starch or iodine - were able to cross the model cell membrane? (Explain how the evidence supports your answer.)

  2. Which particles were unable to cross the model cell membrane?

  3. What is the function of a cell membrane?

  4. What needs to go into a real cell?

  5. What needs to go out of a real cell?

Why does iodine pass through the membrane but corn starch does not?

Look at the molecular diagrams for the two substances:

Corn Starch:

Iodine:

Cleanup guidelines:

• Throw tape, used bags and broken rubber bands into the trash.

• Pile re-usable rubber bands next to the sink.

• Dump liquids down the drain.

• Wash (with soap) all cups and set them upside down to dry.

Part 3: Eggs and Osmosis

A chicken egg is a single, very large, very excellent cell . . . metaphor, that is.

Soak eggs in vinegar overnight until the shells brush off easily.

We will put one de-shelled egg in each of the following four liquids, but first . . .

In your journal, write one hypothesis about what you think will happen to your egg (swell/shrink/stay the same, change color, etc) when put in one of the following liquids (your choice).

1. Green Food Coloring + Water

2. Corn Syrup

3. Red Tempera Paint + Water

4. Water

Put the eggs in the four liquids, and leave them there for multiple days.

After a few days, the teacher will then take out and show the four eggs to the class.

In your journal, record your observations for what happened to each of the four eggs.

1. Water with Green Food Coloring

2. Corn Syrup

3. Red Tempera Paint

4. Water

As a class, go over the Egg Notes for explanations of what happened with the eggs.

Then, break apart the eggs to observe the inside.

Cell Experiments Extension 1 (*): Amoeba Sisters Eggs

Watch the Amoeba Sisters Osmosis Movie (9 min). Complete the Amoeba Sisters Osmosis Worksheet.

Cell Experiments Extension 2 (*): Cell Cooking Project

Cook and/or bake food items that contain cells.

Do a bit of research on what happens to cells in food when they are cooked or otherwise processed (blended, grated, etc.).

Prepare and deliver a lesson to your class in which you teach students how cells change when cooked.

Bring the food items in to share with the class - a cell party!