[美国课堂系列·生物学] Cells. Potato sailor Lab report

Potato sailor lab report

Jinglu Sun, 5^th period

Introduction:

A shipwrecked sailor was found dead after drinking sea water. To find out the real reason of the sailor’s death, we are doing a ‘Potato Sailor lab’, to see how hypertonic solution (salt) can effect the human cells. We think that it potato cells are going to behave like the Sailor cells. If the concentration of solution increases, the size of the potato will decrease, and if the concentration decreases, the size of our potato will expand. The independent variable is the concentration of solution, the dependent variables are the sizes and the flexibilities of the potatoes. Variables we can control are the concentration of solution, original size of potato and time of experiment. If the solution wasn’t controlled, we’ve lost the whole point of doing this experiment, since we’ll have no data to compare. If the original potato sizes weren’t controlled, then the results won’t match up our statement, because there are no relativities between them. If the time of experiment wasn’t controlled, there won’t be the same result, the time has to be identical.

Procedures:

1. In order to determine if the salt in the water has an effect on the potato cells, we need to first cut 4 pieces of potato to represent the sailor. These pieces would be 1 cm square on the ends and 5cm long. The goal is to end up with four pieces of potato that are exactly the same.

2. Now mix 3 different salt-water solutions so that the have a concentration of 10%, 5%, and 1% salt. You will need 50ml of each solution for each piece of potato. The 4^th piece of potato should be placed in 50ml of tap water (0% concentration).

3. Label the cups so that you know the concentration of each during observations on day 2.

4. To determine the effect of salt water, record the dimension of the potato pieces and make a qualitative observation on the crispness of the potato piece.

5. Place a potato slice into each of 4 cups. Cover the cups with plastic wrap and secure with a rubber band.

6. (Day 2) Measure the dimensions of the potato pieces and record any changes in the data table. Use a plus (+) to indicate if the piece has grown and a minus (-) to indicate if the piece has shrunk. Record a qualitative observation on the crispness of the potato.

How to get these solutions (10% solution is already given.):

(1) Measure 50ml of 10% solution and pour into cup A

(2) Measure 30ml of 10% solution and 30ml of tap water (0% concentration), mix them together and get 60ml of 5% solution. Pour 50ml of it into cup B and we will still have 10ml leftovers.

(3) Mix the leftover with 40ml tap water together and get 50 ml of 1% solution. Pour all of them into cup C

(4) Measure 50ml of tap water and directly pour all of them into cup D.

Data table:

Conclusion:

After dipping potatoes in different solutions for a day, we made our observations. Results are shown on the data table above. All the potatoes started off hard, juicy and flexible. But on the day after, potatoes in hypotonic solutions began to swell in sizes. The crispness changed too, it became very hard and nonflexible. On the other hand, Potatoes dipped in hypertonic solutions shrunk in sizes, and was smoother than before, one was even shriveled! One of the potatoes hardly changed at all, and that was the one in the isotonic solution, the size of the potato expanded a little bit, and it was harder than before. The data truly did support our hypothesis. Hypotonic solutions made cells swell, hypertonic solutions made cells shrunk. And isotonic solutions hardly changed anything. According to our observations, the hypothesis needn’t to be changed.