Question

Dialysis bags or model “cells” (A, B, C and D) are placed in beakers containing a 20% sucrose solution. Each model “cell” contains an unknown concentration of sucrose solution. Every 15 minutes, the model “cells” are weighed and the data entered in the table below. Table: Mass of Model “Cells” Containing Different Concentrations of Sucrose Time (minutes) is 0,15,30,45. “Cell” containing solution A is 11.4, 11.3, 11.2,11.3(mass grams) “Cell” containing solution B is 12.5, 13, 13.5, 14(mass grams) “Cell” containing solution C is 10.8,9.6, 8.2, 7.2(mass grams) “Cell” containing solution D is 10.8, 10.2, 9.5, 9.2(mass grams) what is the Movement of Water, % Sucrose in “Cell” & Tonicity in “Cell” of each cell (A-D)

a) Use the data in the table to determine the movement of water. Choose from “Into the cell”, “Out of the cell” or “No net movement of water” Write your answer in the row of the table labeled “Movement of Water”.

b) Based on the movement of water, you can determine what the concentration each solution must have been at the beginning of the experiment for each model “cell” A-D. Choose from 40%, 20%, 15% or 10%. Write your answer in the row of the table labeled “% Sucrose in Cell”.

c) Determine whether each sucrose solution in the “cell” is “hypertonic”, “isotonic” or “hypotonic” relative to the solution outside the “cell”. Write your answer in the row of the table labeled “Tonicity in Cell”. Answer the questions below about Part II of this exercise:

1) A. Explain why was there little or no weight change for the model “cell” containing solution A?

B. This system is said to be at equilibrium. Explain what equilibrium means in terms of the movement of water across the plasma membrane of a cell?

2) The model “cell” containing solution B gained weight. Therefore, the water moved _________ the “cell”. Explain why the water moved as it did in this model system.

3) Model “cells” C and D both lost weight. Therefore, the water moved _________ the “cell”. Explain why the water moved as it did in these systems.

4) A. “Cell” C lost more weight than “cell” D over the same amount of time (60 min). Therefore, “cell” C lost water at a slower or faster rate than “cell” D. (circle one)

B. Explain the cause of the difference in the rate of water loss for “cell” C and D.

5) Do you see a pattern of how water flows into or out of the cell based on the concentration of solute?

Water always moves from a ______________tonic solution to a ____________tonic solution.

6) In the experiment your group will design, you will be using a piece of potato composed of many living cells. Based upon what you have learned about osmosis and tonicity, predict whether a potato core would gain weight, lose weight or stay about the same weight if you placed it in each of the following solutions: Hypertonic – Isotonic - Hypotonic –