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Plasmolysis " Wet Lab"

Exploratory Activity: Osmosis in Elodea Cells or Onion Cells 


Introduction: One of the functions of the cell membrane is to control the flow of materials into and out of the cell. In this investigation, you will observe the effects of placing plant cells in solutions of various concentrations.

Materials: Elodea leaves or red onion, microscope slides, cover slips, microscope, distilled water or tap water, 2% salt solution, paper towel.

Methods: Prepare a wet mount of an Elodea leaf or red onion skin with tap water. Observe the leaf at 40X and record your observations. Increase the magnification to 100X, observe, and record your observations. 

Remove the slide from the stage of the microscope. Place 2 drops of the 5% salt solution on the slide at the edge of the cover slip. Tear off a small piece of paper towel and place the torn edge on the slide at the edge of the cover slip that is opposite the side where the salt solution was placed. The piece of towel should begin to soak up water, drawing the salt solution under the cover slip as it does so. 
Picture
Methods (continued): Return the slide to the microscope stage and repeat the observations of the cells at 40X and 100X. Record your observations. You may find it even more dramatic to look at 400x.  Repeat the above procedure with the other plant sample (Elodea or onion). Record your observations. Remove the slide from the stage, clean it and the cover slip, and put it away. Put the microscope on low power and put it away.

Observations:

Prepare sketches of a group of Elodea cells or Onion cells under each set of conditions. Label the sketches to note the cell structures that you can identify. Be sure to note any changes in the color, size, and shape of the cells. Make your sketches as accurate as possible.

This can be made much more quantitative by measuring the distance from the tonoplast (the membrane around the vacuole) to the plasma membrane using an ocular micrometer.  The images and directions for doing this are below.
Picture
what an ocular micrometer looks like - will be inserted into one of the eyepieces of your objective microscrope
Picture
what you see through the ocular micrometer (lens)
Picture
a stage micrometer (slide) and what it looks like under the microscope
Picture
Conclusions: Answer the following questions.

  1. What is the shape of the typical Elodea cell or Onion cell?
  2. What are the small green blobs found inside the cells? What is their function?
  3. What happens to the cells as the salt water flows under the cover slip?
  4. What happens to the cells if/when the salt water is flushed out with distilled water?
  5. Elodea normally lives in fresh water. What changes would you observe in the cells of an Elodea plant that was suddenly moved from fresh water to salt water? Why? 
  6. When cutting onions, your eyes may cry.  What is in the onion that makes you cry?  Would salt do anything to that substance that makes you cry? 

Plasmolysis Dry Lab 

experimental design

Picture
1.  suggest a general research question.

2.  suggest a specific research question.

3.  identify the independent variable;
     is the range sufficient?

4.  identify the dependent variable; are the  sufficient replicates?

5.  what other variables could influence  results?  how could they be controlled?


data analysis

Picture
1.  where do the values for the x axis come from?

2.  where do the values for the y axis come from?
    a.  what does a positive change in mass mean?
    b.  what does a negative change in mass mean?

3.  What can be learned from finding the x-intercept?

4.  how should error be represented on each axis?

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  • Home
  • SL Bio/Bio 2
    • SL/HL test review
    • SL Bio Blog/Review Discussion Site
    • Name that Sound
    • SL Bio - Topics >
      • Cells >
        • Surface Area/Volume Lab >
          • Types of Errors - more notes.
        • Processing Microscope Data
        • Soap Bubble Membranes
        • Plasmolysis Lab
        • Surface Area/Volume LabHL16 >
          • Types of Errors - more notes.
        • Cell Cycle Timing Lab
      • Biochemistry >
        • Enzyme Lab
        • Photosynthesis Lab
      • Genetics
      • Evolution
      • Ecology SL/Bio2
      • Physiology >
        • Sheep Heart dissection
        • Sheep Brain Dissection
      • SL Option A Neurobiology
  • SL Bio/Bio 2 (pre-2015 exams)
    • SL Bio - Topics >
      • Evolution >
        • Natural Selection Web Activities
        • Paper Worm Simulation - Data Collection and Processing
        • Coacervate Lab
        • Hominid Evolution - Skull Lab
      • Classification
      • Biochemistry >
        • Surface Tension Lab
        • Molecules of Life - Modeling Activity
        • Jmol molecule visualizations
        • Playdough and Toobers!
        • Enzyme Lab
      • SL Genetics >
        • Sockosomes/Chromosocks
      • Biotechnology >
        • DNA gel
        • Bacterial transformation lab
      • Physiology >
        • Digestion
        • Circulation/Gas Exchange >
          • Sheep Heart dissection
        • Nervous system
        • Nutrition - Option A
        • Defense Against Disease
        • Reproduction
      • Ecology >
        • Ecology DBQ practice
        • Population Growth Simulation
        • Emerging Disease Webquest
  • HL BIo Year 1 (pre-2015 exams)
    • Year 1 - Topics >
      • Cells >
        • Processing Microscope Data
        • Surface Area/Volume Lab >
          • Types of Errors - more notes.
        • Plasmolysis Lab
        • Cell Cycle Timing Lab
      • Biochemistry >
        • Surface Tension Lab
        • Molecules of Life - Modeling Activity
        • Jmol molecule visualizations
        • Playdough and Toobers!
        • Race for the Double Helix movie
        • Extraction
      • Metabolism >
        • Enzyme Lab
        • Photosynthesis/Respiration Lab
      • Genetics >
        • Sockosomes/Chromosocks
        • Corn genetics
        • Make a Face
      • Biotechnology >
        • DNA gel
        • Bacterial transformation lab
      • Ecology >
        • Ecology DBQ practice
        • Emerging Disease Webquest
        • Symbiosis in Termites
        • Population Growth Simulation
    • MSON Bioethics >
      • Ethics in Scientific Research
      • Bioethics Films
  • HL Bio Year 1
    • Year One Blog/Review Discussion SIte
    • Year 1 - Topics >
      • EvolutionHL2016
      • CellsHL2016 >
        • Cells: Class Flip Videos
        • Processing Microscope Data HL16
  • HL Bio Year 2
    • SL/HL test review
    • Year Two Blog/Review Discussion Site
    • Ecology Summer Work
    • Year 2 - Topics >
      • Plants
      • Biotechnology_ >
        • DNA gel_
        • Bacterial transformation lab_
        • Microarray
        • Natural Cloning
      • Physiology >
        • Sheep Heart dissection
        • Kidney Dissection
        • Sheep Brain Dissection
        • Chicken Wing Dissection
        • Sea Urchin Embryology
  • HL Bio Year 2 (pre-2015 exam)
    • Year 2 - Topics >
      • Evolution >
        • Natural Selection Web Activities
        • Paper Worm Simulation - Data Collection and Processing
        • Coacervate Lab
        • Hominid Evolution - Skull Lab
      • Phylogeny >
        • Constructing Cladograms
      • Plants >
        • Comparative look at animal developmental switches
        • Plant Microscope exercise
        • Plant Hormone Lab
        • Transpiration Lab
        • Plants and Micrographic Art
        • Plants and Human Art
      • Neurobiology >
        • Preview Topics
        • Neuron Action Potential Simulation
        • Connectome
        • Sheep Brain Dissection
        • Cow Eye Dissection
        • Invertebrate Behavior Lab
        • Altered Reality
        • Human Behavior Lab
      • Physiology >
        • Digestion Demos
        • Sheep Heart dissection
        • Blood typing
        • Kidney Dissection
        • AIDS Global Awareness
        • Virtual ELISA
        • Film - Politics, People and Science of AIDS
        • Chicken Wing Dissection
        • Sea Urchin Embryology
      • Review Project >
        • Review assignments, written by HL students
        • Web 2.0 Tools
  • IB Connections
    • TOK Connections >
      • Natural Sciences - TOK
    • MYP reference site
    • Extended Essay in Biology
    • Group 4 Project
    • Internal Assessment - 1st and 2nd year >
      • Advice on Internal Assessment
      • Uncertainty in calculations
      • t test/TI 83/excel
      • tips on mac excel graphs
      • Notes from IB worldwide report
      • Lab photo album
    • Advice for IB Papers >
      • Advice on IB Examinations
    • IB Learner Profile - How does HL Bio fit in?
  • Resources
    • for our SL friends
    • BioNinja
    • iBiology
    • Click4biology
    • Biozone Weblinks
    • IB Biology video review
    • Smullen Powerpoint
    • Wapole text
    • IB Guides
    • Recommended biology tutorials (besides IB)
    • Practice Tests/Exam Dates/Review Materials >
      • Review assignments, written by HL students
      • Knowledge audits
      • Biology Narratives - Review Activity
      • Organizational review assignment
      • Year 1 Final Review
      • Quizlets and Other Shared Reviews
  • Clubs and Committees
    • Science Olympiad >
      • 2012 Science Olympiad Team in action
      • Photos from the 2013 Olympiad
    • Bioethics Bowl >
      • Villanova Bioethics Competition >
        • Team Pictures - 2012
      • Peace and Ecology Committee
  • Biotechnology