Pre lab assignment 1 osmosis and tonicity practice problems

Student's Name Instructor PRE-LAB ASSIGNMENT #1: OSMOSIS AND TONICITY PRACTICE PROBLEMS To be completed before beginning week one of the Osmosis and the Scientific Method Lab. Part I: Dialysis bags (“cells”) are placed in three different beakers. The cells, as well as the beakers, contain different aqueous solutions of NaCl. For each of the beakers, answer the questions below. Cell # 1 contains 15% NaCl Beaker contains 35% NaCl Cell # 1 contains 50% NaCl Beaker contains 25% NaCl Cell # 1 contains 30% NaCl Beaker contains 30% NaCl Beaker #1: a) The solution inside the cell contains 50% NaCl and % water. b) The beaker contains 25% NaCl and % water. c) The solution inside cell #1 is tonic to the solution outside cell #1. d) The solution outside cell #1 is tonic to the solution inside cell #1. e) In which direction will water move? (circle one below) Into the cell Out of the cell No net movement of water f) Draw an arrow or arrows on Beaker #1 above to show the movement of water. g) Explain how you determined the movement of water. h) Over time, what will happen to cell #1? (circle one below) Shrinks Swells Remains the same size 1 Beaker #2: a) The solution inside the cell contains 30% NaCl and b) The beaker contains 30% NaCl and % water. % water. c) The solution inside cell #2 is tonic to the solution outside cell #2. d) The solution outside cell #2 is tonic to the solution inside cell #2. e) In which direction will water move? (circle one below) Into the cell Out of the cell No net movement of water f) Draw an arrow or arrows on Beaker #2 above to show the movement of water. g) Explain how you determined the movement of water. h) Over time, what will happen to cell #2? (circle one below) Shrinks Swells Remains the same size Beaker #3: a) The solution inside the cell contains 15% NaCl and b) The beaker contains 35% NaCl and % water. % water. c) The solution inside cell #3 is tonic to the solution outside cell #3. d) The solution outside cell #3 is tonic to the solution inside cell #3. e) In which direction will water move? (circle one below) Into the cell Out of the cell No net movement of water f) Draw an arrow or arrows on Beaker #3 above to show the movement of water. g) Explain how you determined the movement of water. h) Over time, what will happen to cell #3? (circle one below) Shrinks Swells Remains the same size 2 Part II: 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 "Cell"A "Cell" B "Cell" C "Cell" D Mass (grams) Mass (grams) Mass (grams) Mass (grams) 0 11.4 12.5 10.8 10.8 15 30 11.3 11.2 13 13.5 9.6 8.2 10.2 9.5 45 11.3 14 7.2 9.2 Time (minutes) Movement of Water % Sucrose in "Cell" Tonicity in "Cell" 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” Write your answer in the row labeled “Movement of Water”. b) Based on the movement of water, you can determine the concentration inside each model “cell” A-D. Choose from 40%, 20%, 15% or 10%. Write your answer in the row 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 labeled “Tonicity in Cell”. 3 Answer the questions below about Part II of this exercise: 1) A. Explain why there was little or no mass 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 Explain why the water moved as it did in these systems. the “cell”. 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 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.