Expert: Walter Hintz - 10/12/2009

Question
I have an "experiment" if you will that I have to record data on. The only information given is this:

1. 3 sac of tubing were filled with a 2M sucrose solution. The tubing is permeable only to water.
2. Each sac was weighed and then placed into a beaker containing an unknown concentration of sucrose.
3. The sacs were allowed to remain in the beakers for 2 hrs. They were removed and reweighed. the results are given on the table below.

                       INITIAL WEIGHT OF SAC      FINAL WT OF SAC
    A-2M SUCROSE            20 GRAMS                 8 GRAMS
    B-2M SUCROSE            20 GRAMS                 18 GRAMS
    C - 2M SUCROSE          20 GRAMS                 36 GRAMS

Question 1) how does the tubing act as a cel membrane?
2) explain why there is a difference in weights at the end of the experiment?
3)Identify each solution Hypertonic, Hypotonic, or Isotonic?
Solution A
solution B
Solution C
4) what osmotic problem does a bacterium encounter in fresh water?
5) In salt water?

I am totally lost as to what I am supposed to be doing, and I truly don't understand a bit of it. Can u please halp??

Thanks in advance,
Shannon

Answer
 Question 1. The tubing only simulates a cell membrane because it allows water to pas  through
Question 2 There was a difference in the sucrose concentration in the beakers
 Question 3 Sacs A and B were in a beaker with a solution greater then 2M glucose so they lost water through osmosis and the concentration in the beakers was greater in A then in B
Sac B was in a beaker with no sucrose so it gained water
 Remember that with osmosis water moves from a area of high concentration to on of low concentration
 Solution A and B were hypotonic and C was hypertonic

Question 4 Bacterium in fresh water will gain water through osmosis
Question 5  In salt water they will lose water and dehydrate. That is why salted foods can be preserved.  Bacteria that land on a salted food will dehydrate