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BISC 101 Lecture Notes - Lecture 3: European Route E40, Treatment And Control Groups, Ethylene

1382 views6 pages
silvertermite629
15 Dec 2017
School
Simon Fraser University
Department
Biological Sciences
Course
BISC 101
Professor
Tony Williams

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Document Summary

For eggs placed in a sucrose solution, an increase in sucrose concentration causes an increase in movement of water out of the egg. We assigned 10 eggs to each treatment group. If an experiment can be replicated, it means it is more likely to be correct. Go observe the eggs and record your observations. Basically, the solution is isotonic at 30% sucrose. Any more sucrose results in a hypertonic solution, so the egg will lose water. Any less sucrose results in a hypotonic solution, so the egg will gain water. Yes, otherwise the egg would not be gaining or losing weight. No, the sucrose molecule is too large to pass through the membrane freely. Solution is hypotonic compared to the solution inside the egg. The concentration outside is less than inside, so water must move into the egg to dilute it. The movement of water into the egg causes it to gain weight.

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Related Questions

Experiment 2: Osmosis - Direction and ConcentrationGradients

In this experiment, we will investigate the effect of soluteconcentration on osmosis. A semi-permeable membrane (dialysistubing) and sucrose will create an osmotic environment similar tothat of a cell. This selective permeability allows us to examinethe net movement of water across the membrane. You will begin theexperiment with a 30% sucrose solution, and perform a set of serialdilutions to create lower concentration solutions. Some of thesucrose concentrations will be membrane permeable; while otherswill not be permeable (can you determine why this is?).

Materials

(3) 250 mL Beakers

(1) 10 mL Graduated Cylinder

(1) 100 mL Graduated Cylinder

Permanent Marker

*8 Rubber Bands (2 blue, 2 green, 2 red, and 2 yellow)

60 g Sucrose (Sugar) Powder, C12H22O11

4 Waste Beakers (any volume)

*Paper Towels

*Scissors

*Stopwatch

*Water

*(4) 15 cm. Pieces of Dialysis Tubing

*Contains latex. Please handle wearing safety gloves if you have alatex allergy.



*You Must Provide

*Be sure to measure and cut only the length you need for thisexperiment. Reserve the remainder for later experiments.

Procedure

1. Use the permanent marker to label the three 250 mL beakers as 1,2, and 3.

2. Cut four strips of dialysis tubing, each 15.0 cm long. FillBeaker 3 with 100 mL of water and submerge the four pieces ofdialysis tubing in the water for at least 10 minutes.

3. After 10 minutes, remove one piece of tubing from the beaker.Use your thumb and pointer finger to rub the tubing between yourfingers; this will open the tubing. Close one end of the tubing byfolding over 3.0 cm of one end (this will become the bottom). Foldit again and secure with a yellow rubber band (use

4. Tie a knot in the remaining dialysis tubing just above or justbelow the rubber band. This will create a seal and ensures thatsolution will not leak out of the tube later in theexperiment.

5. To test that no solution can leak out, add a few drops of waterto the tubing and look for water leakage. If any water leaks,tighten the rubber band and/or the knot in the tubing. Make sureyou pour the water out of the tubing before continuing to the nextstep.

6. Repeat Steps 4 - 5 with the three remaining dialysis tubes,using each of the three remaining rubber band colors.

7. Reconstitute the sucrose powder according to the instructionsprovided on the bottle�s label (your kit contains 60 g of sucrosein a chemical bottle) . This will create 200 mL of a 30% stocksucrose solution.

8. Use Table 2 to create additional sucrose solutions that are 30%,15% and 3% concentrated, respectively. Use the graduated cylinderand waste beakers to create these solutions. Set these solutionsaside.

Table 2: Serial Dilution Instructions

Sucrose Solution mL of Stock Sucrose Solution Needed mL of WaterNeeded

30% 10 0

15% 5 5

3% 1 9

3% 1 9

9. Pour 150 mL of the remaining stock sucrose solution into Beaker1.

10. Use some of the remaining stock sucrose solution to create anadditional 200 mL of a 3% sucrose solution into Beaker 2.

Hint: Use your knowledge of serial dilutions to create this final,3% sucrose solution.

11. Measure and pour 10 mL of the remaining 30% sucrose solutioninto the dialysis bag with the yellow rubber band. Seal the top ofthis tubing with the remaining yellow rubber band.

12. Measure and pour 10 mL of the 15% sucrose solution in the bagwith the red rubber band, and seal the top of the dialysis tubingwith the remaining red rubber band. 10 mL of the 3% sucrosesolution in the bag with the blue rubber band, and seal thedialysis tubing with the remaining blue rubber band. The final 10mL of 3% sucrose solution in the bag with the green rubber band.Seal the dialysis tubing with the remaining green rubberband.

13. Verify and record the initial volume of solution from each bagin Table 3.



Figure 8: The dialysis bags are filled with varying concentrationsof sucrose solution and placed in one of two beakers.

14. Place the yellow, red, and blue banded tubing in Beaker 2.Place the green banded tubing in Beaker 1 (Figure 8).

15. Hypothesize whether water will flow in or out of each dialysisbag. Include your hypotheses, along with supporting scientificreasoning in the Hypotheses section at the end of thisprocedure.

16. Allow the bags to sit for one hour. While waiting, pour out thewater in the 250 mL beaker that was used to soak the dialysistubing in Step 1. You will use the beaker in Step 19.

17. After allowing the tubing to sit for one hour, remove them fromthe beakers.

18. Carefully open the tubing. The top of the tubing may need to becut off/removed as they tend to dry out over the course of an hour.Measure the solution volumes of each dialysis bag using the 100 mLgraduated cylinder. Make sure to empty and dry the cylindercompletely between each sample.

19. Record your data in Table 3.

Data Tables and Post-Lab Assessment

Table 3: Sucrose Concentration vs. TubingPermeability

Table 3: Sucrose Concentration vs. TubingPermeability

Band Color

% Sucrose in Beaker

% Sucrose in Bag

Initial Volume (mL)

Final Volume (mL)

Net Displacement (mL)

Yellow

Red

Blue

Green

Hypothesis:

For each of the tubing pieces, identify whether the solutioninside was hypotonic, hypertonic, or isotonic in comparison to thebeaker solution in which it was placed.

Which tubing increased the most in volume? Explain why thishappened.

What do the results of this experiment this tell you about therelative tonicity between the contents of the tubing and thesolution in the beaker?

What would happen if the tubing with the yellow band was placedin a beaker of distilled water?

How are excess salts that accumulate in cells transferred to theblood stream so they can be removed from the body? Be sure toexplain how this process works in terms of tonicity.

If you wanted water to flow out of a tubing piece filled with a50% solution, what would the minimum concentration of the beakersolution need to be? Explain your answer using scientificevidence.

How is this experiment similar to the way a cell membrane worksin the body? How is it different? Be specific with yourresponse.

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 –