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Week 5 Diffusion and Osmosis Lab and Post-Lab Questions

You will use the Diffusion osmosis lab.docx to complete this lab and answer the questions in the document.

Please type your answers to the postlab questions in a separate word document and submit that to Canvas.

BIOL&160 lab, Spring 2020                                                  Name: _______________________

DUE: May 11-15, 2020

 

Week 5 Diffusion and Osmosis Lab and Post-Lab Questions

 

Purposes:

  • Help you visualize what is happening when diffusion occurs, and how temperature, molecule size and membrane permeability affect diffusion.
  • Show how cells exchange O2 and CO2 by diffusion.
  • Run an osmosis experiment.
  • Define hypertonic, hypotonic, and isotonic solutions, and explore the effects that each solution has on plant and animal cells.

Task:

Please follow the instructions provided below and work through the following exercises and complete all 4 parts for this lab. Contact your instructor as soon as possible if you cannot get the websites to work; alternate arrangements will require some scheduling time! Please type your answers to the post-lab questions in this document, save it as a Word document, and upload it to Canvas by the due date provided by your instructor.

Criteria for Success:

The successful student will spend meaningful time exploring all simulations. Your grade will reflect your ability to follow the instructions within the exercises and interpret the information provided.

Diffusion and Osmosis Lab Instructions:

Part 1:  Brownian Motion

All atoms and molecules vibrate, even the ones in the computer that you are working on. When this vibration occurs with atoms or molecules in a fluid (liquid or gas), it is called Brownian motion.

 

  • Watch the following YouTube video on Brownian motion (https://www.youtube.com/watch?v=s1mn-ud2Cx0) and observe the slight movement/vibration of the Carmine dye particles (red particles). This video is only 20 seconds long and you are watching the movement of the Carmine dye molecules as you would have in the lab.
    1. Are large dye particles or small dye particles moving/vibrating faster?

 

  • Click on the following link for the Panopto recording (https://cbc.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=9a5acf2a-77d6-4599-8fd6-abb000110216) that will walk you through the next set of exercises. You will play parts of the video and then pause the video in order to run the simulation.

Go to the following website, opening it in a different tab, because we will be using several simulations from the Molecular Workbench website. (http://mw.concord.org/nextgen/#interactives/biology/diffusion-bio/diffusion-bio-drop)

  1. In “Diffusion of a Drop” portion of the simulation, is the red dye molecule moving in a constant direction or does it move in random directions changing its course frequently?
  2. What causes the red dye molecule to move and change direction?

 

Part 2:  Diffusion

As seen in the previous section, atoms or molecules in a fluid (liquid or gas) vibrate and these vibrations caused the molecules to bump into each other, causing them to move randomly. Diffusion is the random movement of molecules from an area of high concentration to an area of low concentration.  Use the instruction video provided above to give you directions for the following simulations:

 

  • Observe diffusion.
    1. Did the red dye molecules stay close to each other and move as a group around the simulation? If not, describe the distribution of the molecules at the end of the simulation.

 

  • Temperatures effect on diffusion.
    1. Using the data that you collected in the simulation, explain your results of changing the temperature from low to high affected the amount of time it took for each simulation to run to completion.

 

  • Diffusion across a Semipermeable Membrane.
    1. With the “small” pore size, did any of your green molecules cross the semipermeable membrane? How about the blue molecules?

 

  1. With the “medium” pore size, did any of your green molecules cross the semipermeable membrane? If yes, how many were on the right side of the membrane at the end of the simulation? How many were still on the left side?

 

  1. With the “large” pore size, did any of your green molecules cross the semipermeable membrane? Again, count the number of green molecules on both the right and the left side of the membrane.

 

  1. Using your numbers from the “large” pore size, describe how the movement of the green molecules differed in this part when compared to the previous simulation when the pore size was about the same size as the green molecules.

 

  • Diffusion of gases across a permeable membrane.
    1. If O2 is “high” outside and “low” inside, approximately how long did it take for the O2 levels to become approximately equal on both sides of the membrane (outside and inside of the cell)?
    2. When you let the simulation run for the additional 10 seconds, what happened to the O2 levels after they became approximately equal on both sides of the membrane? Additionally, explain why this happened.

 

  1. If O2 is “high” outside and “low” inside and CO2 is “low” outside and “high” inside, approximately how long did it take for the O2 levels to become approximately equal on both sides of the membrane (outside and inside of the cell)?

 

  1. As we will see in Chapter 6 of your textbook, cells use O2 and produce CO2 as part of their metabolism. Using your observations from this simulation, describe how a cell acquires the O2 the cell needs for its metabolic processes and how a cell gets rid of the CO2 that is doesn’t need and can actually be harmful to the cell.

 

Part 3:  Osmosis

Osmosis is the diffusion of water molecules. Water molecules can be “free”, or they can be bonded to another molecule. Osmosis is the diffusion of free water molecules from an area of high concentration to an area of low concentration of free water molecules.  Use the instructions below to give you directions for the following simulations:

 

  • Go to the following website and complete the osmosis experiment. (https://video.esc4.net/video/assets/Science/Biology/Gateway Resources/cell homeostasis virtual lab – activity/index.html)

 

  • You do not have to make a graph as the website suggests.

 

  • Follow the prompts provided by the simulation.

 

 

  • Complete the lab simulation, record your data in a table like the one below, and answer the following questions.

 

  Treatment A Control Treatment B 0% sugar Treatment C 5% sugar Treatment D 10% sugar Treatment E 15% sugar
Beginning Weight in Grams          
End Weight in Grams          
Percent Weight Change *          

 

* Percent weight change = (weight at end – weight at beginning) x 100                                                                        weight at beginning

 

  • Using the Data Table that you generated above in question 7, answer the following:

 

  1. Which dialysis tubes had little or no change in the mass after the 24- hour period
    1. “A”, “C”, “E”
    2. “C”, “D”
  • “A”, “D”

 

  1. Why was pure water used as a control group?
    1. The control group provides a standard for comparison for the experimental group.
    2. The control group represents a real cell because real cells contain water.
  • The control group was not necessary.

 

  1. Why didn’t the mass of dialysis tubes “A” and “D” change over the 24-hour time frame?
    1. The dialysis tubing material was clogged.
    2. The concentration both inside and outside the dialysis tube is the same.
  • The pressure of the dialysis tubing membrane stabilizes the flow of water.

 

  1. Which statement below best describes how a cell responds to its’ external environment?
    1. The difference in concentration of solids in a cell’s external environment has no effect on how water moves into and out of a cell.
    2. If the concentration of solids in the cell’s external environments is greater than the internal environment, water passes out of the cell.
  • If the concentration of solids in the cell’s external environment is less than the internal environment, the water passes out of the cell.
  • This virtual experiment was conducted at room temperature, which is about 20°C, and ran for 24 hours.
    1. Using your knowledge about diffusion from the previous exercises, would you raise or lower the temperature in order to get similar results in a shorter period of time?
    2. Using your knowledge from the previous exercises, explain why your choice would work.

Part 4:  Isotonic, hypertonic and hypotonic solutions

When we say a solution is isotonic, hypertonic or hypotonic, we are comparing two solutions in neighboring compartments. For example, we cannot just say that “solution A is isotonic” all by itself, because no other solution is referenced. However, we can say that “solution A is isotonic as compared to solution B.”

 

Go to the following website, watch the video about osmosis (http://www.glencoe.com/sites/common_assets/science/virtual_labs/LS03/LS03.html), and answer the questions below.

 

  • Using the information from the video that you just watched, define the following terms in your own words:
    1. Isotonic solution
    2. Hypertonic solution
    3. Hypotonic solution

 

  • You have two solutions, solution C and solution D.
    1. Solution D is isotonic, this means that solution C must be _______.

(hypertonic, hypotonic, or isotonic)

  1. Solution C is hypotonic, this means that solution D must be _____.

(hypertonic, hypotonic, or isotonic)

 

Part 5:  The effect of Isotonic, hypertonic and hypotonic solutions on animal and plant cell

Organisms try to maintain a homeostatic environment for their cells so that they can have a constant internal conditions.  Organisms that do not have a cell wall (remind yourself which kinds of cells do not have cell walls…) need to maintain homeostasis, but because osmosis is ongoing, the cells need to be in an isotonic environment. In contrast, organisms like plants have a cell wall and try to keep the inside of the cell hypertonic compared to the hypotonic surroundings of the cell in order to maintain homeostasis. For plants, the cell wall keeps them from bursting and the pressure that the cell puts on the cell wall gives the plant rigidity, this is why plants that need water will wilt.

 

 

  • In the above simulation, you will place the red blood cell into the solutions by dragging the red blood cell into the appropriate solution.
  1. Place the red blood cell into the hypotonic solution.
    1. Describe what physically happens to the red blood cell, if anything?
    2. If the solution is hypotonic, the red blood cell is _____. (hypertonic, hypotonic, or isotonic)
  • Which way is the net movement of water between the solution and the red blood cell? Choose; into the cell; out of the cell; both in and out of the cell; or neither into nor out of the cell.

 

  1. Place the red blood cell into the isotonic solution.
    1. Describe what physically happens to the red blood cell, if anything?
    2. If the solution is isotonic, the red blood cell is _____. (hypertonic, hypotonic, or isotonic)
  • Which way is the net movement of water between the solution and the red blood cell? Choose; into the cell; out of the cell; both in and out of the cell; or neither into nor out of the cell.

 

  1. Place the red blood cell into the hypertonic solution.
    1. Describe what physically happens to the red blood cell, if anything?
    2. If the solution is hypertonic, the red blood cell is _____. (hypertonic, hypotonic, or isotonic)
  • Which way is the net movement of water between the solution and the red blood cell? Choose; into the cell; out of the cell; both in and out of the cell; or neither into nor out of the cell.

 

  • In the above simulation, you will be place the Elodea plant cell into the appropriate solution by dragging the plant cell into the solutions in reverse order compared to question 10.

 

  1. Place the Elodea plant cell into the hypertonic solution.
    1. Describe what physically happens to the Elodea plant cell, if anything?
    2. If the solution is hypertonic, the Elodea plant cell is _____. (hypertonic, hypotonic, or isotonic)
  • Which way is the net movement of water between the solution and the Elodea plant cell? Choose; into the cell; out of the cell; both in and out of the cell; or neither into nor out of the cell.

 

  1. Place the Elodea plant cell into the isotonic solution.
    1. Describe what physically happens to the Elodea plant cell, if anything?
    2. If the solution is isotonic, the Elodea plant cell is _____. (hypertonic, hypotonic, or isotonic)
  • Which way is the net movement of water between the solution and the Elodea plant cell? Choose; into the cell; out of the cell; both in and out of the cell; or neither into nor out of the cell.

 

  1. Place the Elodea plant cell into the hypotonic solution.
    1. Describe what physically happens to the Elodea plant cell, if anything?
    2. If the solution is hypotonic, the Elodea plant cell is _____. (hypertonic, hypotonic, or isotonic)
  • Which way is the net movement of water between the solution and the Elodea plant cell? Choose; into the cell; out of the cell; both in and out of the cell; or neither into nor out of the cell.

 

  • In the above simulation, you will be placing the paramecium (a single celled protist that has characteristics of plants, it can photosynthesize, and animals, it has cilia and can ingest food) into the solutions by dragging the paramecium into the solution.

 

  1. Place the paramecium into the hypertonic solution.
    1. Describe what physically happens to the paramecium, if anything?
    2. If the solution is hypertonic, the paramecium is _____. (hypertonic, hypotonic, or isotonic)
  • Which way is the net movement of water between the solution and the paramecium? Choose; into the cell; out of the cell; both in and out of the cell; or neither into nor out of the cell.

 

  1. Place the paramecium into the isotonic solution.
    1. Describe what physically happens to the paramecium, if anything?
    2. If the solution is isotonic, the paramecium is _____. (hypertonic, hypotonic, or isotonic)
  • Which way is the net movement of water between the solution and the paramecium? Choose; into the cell; out of the cell; both in and out of the cell; or neither into nor out of the cell.

 

  1. Place the paramecium into the hypotonic solution.
    1. Describe what physically happens to the paramecium, if anything?
    2. If the solution is hypotonic, the paramecium is _____. (hypertonic, hypotonic, or isotonic)
  • Which way is the net movement of water between the solution and the paramecium? Choose; into the cell; out of the cell; both in and out of the cell; or neither into nor out of the cell.

 

  1. Did the paramecium react the way the red blood cell or the Elodea plant cell reacted in the solutions? What were some (more than 1) observations that led you to your conclusion?

 

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