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Thursday 10th December, we did an experiment, in English, with: Mrs WILHELM, Mr VALENTIN, Mr OSWALD and Mr SCHIMMEL.

To conduct the experiment, we needed: a banana, ethanol, detergent, a pipette, distilled water, a mortar and pestle, a couple of test tubes, a watch glass, two beakers, a funnel and a glass rod.

Osmosis

We made two holes in a potato, we filled one hole with salt and left the other one empty. We put the potato in a watch glass which was filled with water. Then we waited a couple of minutes.

After waiting, we observed that the hole full of salt had filled with water. Because the hole was highly concentrated in salt, and to find equilibrium, water was sucked into the hole by osmosis.

Dissolving the membrane

In the second experiment we wanted to dissolve the membrane. First we took a beaker and poured water and oil into it. Then we stirred the mixture with the glass rod and left it to rest. After resting, we observed that oil bubbles had gathered to form a homogeneous layer above the water.

We then added some detergent to the water and oil mixture and stirred it with the glass rod. We then left it to rest a second time. We observed that with detergent the emulsion is stable. The oil layer did not form this time.

The detergent separates fat, and it made the membrane fragile because it consists mainly of lipids (fat).

Collecting the dissolved DNA

Part 1

DNA is soluble in water so in order to conduct this experiment we had to find a way to collect DNA, without using water.

This is what we did:

We took a test tube and poured an oversaturated salt solution into it and added ethanol. In solution the salt was not visible, but when we added ethanol the salt became visible. Salt doesn’t dissolve in ethanol so when we added the ethanol to the oversaturated salt solution the salt solidified.

Part 2

1. We peeled the banana and cut it into small pieces

2. Then we then put the banana pieces into the mortar and added a soup spoon of coarse salt.

3. With the pestle we grounded the mixture to a smooth paste

4. We added 10ml of detergent with the pipette.

5. Then we added 30ml of water with the pipette. And we waited 5 minutes.

6. We filtered the mix to collect the liquid part (filtrate) in a test tube.

7. We covered the filtrate delicately with ethanol. And waited and observed for 10 minutes.

After 10 minutes we observed the banana DNA (medusa) in the ethanol layer, above the banana filtrate layer.

Like salt DNA is soluble in water but not in ethanol, so adding ethanol to banana filtrate allowed us to see and collect banana DNA.

This experiment was fun to do, especially in English.

It helped us better understand what cells are made of.

We hope we can do more experiments like this later in the year.

Bastian Timothy, Menyhart Clélia