BIO 101 Lab 05, Osmosis and Dialysis PDF

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Bio lab 05 for NOVA students ...

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BIO 101 Lab 4: Osmosis and Dialysis To submit, print or edit (in a different color) this lab, complete the activities, scan your work using the free AdobeScan app on your phone or save your document, and upload your scanned PDF or Word file to Canvas. If you have a disability that makes it difficult to complete this lab, please contact your instructor. Please provide your instructor a copy of the Memorandum of Accommodation (MOA) from NVCC Disability Support Services. Objectives: ● ●

Review cell membrane structure and the components that make it a semipermeable barrier. Observe the effect of virtual cells placed in solutions, hypotonic, isotonic, and hypertonic to the cells

Background: Cells and Cell Membrane structure Living cells are filled with an aqueous solution, the cytosol. Many small solutes or particles, are dissolved in this watery cytosol, including ions, nutrients, waste and enzymes. Larger organelles (such as mitochondria and chloroplasts) and large complexes of molecules (e.g. ribosomes) are also located in this cytosol; organelles and complexes combine with the cytosol to form the cytoplasm of cells. The exterior barrier of all cells, is a cell membrane (plasma membrane). Because the cell membrane is comprised of both phospholipids and proteins it is semi-permeable: select molecules can easily pass through the phospholipid bilayer, while other molecules cannot. Phospholipids are comprised of hydrophobic fatty acid tails and polar phospho- heads. In the bilayer, the fatty layers are sandwiched in between the hydrophilic polar heads; one layer of polar heads lines the inside (cytosolic face) of the cell membrane and a second polar head, lines the outside of the cell membrane or surface. Transport through membranes Molecules that can easily pass through a cell membrane are small and nonpolar, such as gases: oxygen, carbon dioxide, and nitrogen. Hydrophobic lipids, (fats and steroids) can dissolve in the hydrophobic fatty layer of the cell membrane and also will diffuse into or out of a cell. Some small molecules (e.g. sugars) and ions (sodium or chloride) can diffuse across a membrane if there is a protein (transport protein or ion channel) These small solutes will move from areas of high concentration to low concentration through a select protein that is part of the membrane. Osmosis occurs when water moves down its gradient. Active transport occurs when a solute, such as sugar, moves against its gradient. Both energy and protein transporters are required for active transport to occur. Osmosis is a type of diffusion Osmosis occurs when water moves by diffusion across a membrane from high water concentration to low lower water concentration. In this case, the solutes are not diffusing because they have positive or negative charge or are too large, and their protein transporter are closed. Tonicity. Three terms refer to the concentrations of solutes in which a cell or organism is placed: ● Isotonic solutions have an equal concentration of solutes outside a cell as the cytosol in the cell (is also referred to as having an equal osmotic pressure) ● Hypotonic solutions have a lower solute concentration outside a cell than the cytosol in the cell ● Hypertonic solutions have a higher solute concentration inside a cell than the cytosol in the cell.

Go to this website and be sure to read every page as your progress through the lab: https://video.esc4.net/video/assets/Science/Biology/Gateway%20Resources/cell%20homeostasis%20virtual%20la b%20-%20activity/index.html This lab will investigate what happens to a cell placed in different environments. To answer this question, you will be working through a virtual lab using different concentrations of sugar in a beaker and dialysis tubing. • The sugar fluid in the beaker represents what? ______Solute________________ • The fluid in the dialysis tubing represents what? ____Solvent_______________ Begin the virtual lab. Follow the prompts; as you work through the process, answer the questions and fill in the data table! Beaker A consists of what? _____________water_______ • This beaker will serve as the ______control_______ for the experiment. Beaker B consists of how much water and how much sugar? ______0________ g sugar, ___1000___ mL � 2� Beaker C consists of how much water and how much sugar? _______50______ g sugar, _____950_mL �2� Beaker D consists of how much water and how much sugar? ______100________ g sugar, ____900__mL �2� Beaker E consists of how much water and how much sugar? ______150_______ g sugar, ____850__ mL �2� Below each beaker in the text box, label A-E and write their % solution.

Beaker A 0%

Beaker B 0%

D Beaker Beaker C 10% 5%

Beaker E 15%

Fill in the data table with the percentage of sugar solution placed in them. Now take the mass of each dialysis tube and place it in its respective beaker. As you take each mass, record on the data table. • The dialysis tubes will remain in each beaker for how long? ____24 hours__________

Now you are going to take the dialysis tubes out of each beaker and take a final mass. • Record this on the data table; • Lastly, calculate the differences in the initial/final mass of each tube Data Table: A B C D Control Experimental Experimental Experimental Beaker Solution % 0% 0% 5% 10% sugar 0% 10% 10% 10% Dialysis Tube Solution% sugar

E Experimental 15% 10%

Initial Mass

17.59g

8.75g

11.24g

10.71g

18.05g

Final Mass

17.66g

10.4g

12.10g

10.57g

15.60g

Amt. of Mass Gained +0.07 +1.65 + 0.86 -0.14 -2.45 (+) or Lost (-) On your beaker drawing, now draw the tubes in the beakers and show the behaviors of the water in the different concentrations of sugar using arrows to show which direction the water is moving. If you can’t draw the tubes, then just describe which way the water is moving in the text box below. Analysis: In the lab, what are 4 variables that remained constant throughout the lab (What stayed the same) ___________Time (24 hours)______________ _______________________Water_____________ ____________Same kind of sugar___________

___________________Same equipment_______

In the lab, which variable is the dependent variable (What you measured in the experiment) ________________________Mass____________________________________________________ In the lab, which variable is independent (The one thing changed by the scientist) ___________________________________________________________________________________________ Looking at your experimental data for Beaker/Tube B. The percent concentration of both fluids is different. There is __0___% sugar in the beaker and ____10____% sugar in the dialysis tube. Now, think of it from the water's point of view. There is ___100_____% water in the beaker and ___90_____% in the dialysis tube. So the beaker has a ________Higher___________ concentration of water than the dialysis tube. When you put the dialysis tube in the beaker, the water will flow across the tube's membrane and ______into_______ the tube.

• The term for the diffusion of water across a membrane from a higher concentration of water to a lower concentration of water is _______osmosis______________; that is what is happening in Beaker B. Now focus on the other 3 experimental beakers (C-E) 1. Which beaker had a higher concentration of sugar solution fluid outside than inside? ___E_____ • If the percent solute concentration is greater in the fluid outside a cell than inside a cell, how will the water flow? The water will flow _____from_______ the cell and ______to_______ the beaker; this means that the cell (tube) will gain or lose mass? _____lose______________

•

This tells you that the type of solution the cell was placed in was ____Hyper solution____________

2. Which beaker had a percent concentration that was equal on both inside/outside the cell? ___beakers A and D ______

•

If the percent solute is equal outside of the cell and inside the cell, how will the water flow? The water will flow _____into___ and _____out_______ of the cell at a ____constant_______ rate.

• • •

This tells you that the type of solution the cell was placed in was _________isotonic___________ Which experimental tube did this happen to? ____B_______________________________ Why does the data show that the tube had lost mass after 24 hours? Explain how this could be. __________________________________________This could be due to a faulty experiment_________________________________________ ___________________________________________________________________________________

3. Which beaker has a higher concentration of sugar solution inside the cell than outside? _____B______ • If the percent solute concentration is greater in the fluid inside a cell than outside a cell, how will the water flow? The water will flow ____into________ the cell and ______from_______ the beaker; this means that the cell (tube) will gain or lose mass? _________gain__________

• •

This means the solution would be ______________hypotonic______ Based on the above analysis, you know that tube C should have gained mass, but the data shows that it lost mass, what might explain this happened? *Hint- do all experiments go according to plan? Could there have been some error?* Explain what you think could have happened to get this result instead of what result you expected to happen. _____Could be a leaky bag ____________________________

4. Why did both Tube A and D had little to no change in mass after 24 hours? _Because They are isotonic solutions, the % in the beaker and the dialysis tube solution was equal. ___ __________________...