osmosis LAb(2)

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Gwinnett Technical College *

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Biology

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Feb 20, 2024

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Name AP Lab 4: Diffusion, Osmosis, and Water Potential Before you begin this lab, review the relevant information in the content and in your textbook. Also prepare by reading over this lab in the AP Biology Investigative Lab Manual on pages S51-S54. Prelab (IMPORTANT): Watch the following video throughout these labs https://www.youtube.com/watch?v=LeS2-6zHn6M Diffusion demo: (min 2:42 of video). Watch the above video carefully, record data below, and answer the analysis questions. In this ac±vity, we will witness the diffusion of different par±cles across a selec±vely permeable membrane. We use the term “selec±vely permeable” to discuss how a membrane lets some par±cles go in or out, but not all par±cles. This membrane is an ar±ficial plas±c tube, not a real cell membrane. It selects par±cles based on their size – if a par±cle is small enough to go through the small holes of the tubing, then it can cross. If a par±cle is too large, then it does not cross. We will have several par±cles inside or outside the cell in this experiment, and we will be able to see what they do over the course of 20-30 minutes. Particles: IKI – has a orange-brown color unless it is in the presence of starch – then it turns blue-black starch glucose – we will use test strips that turn different colors if glucose is present Data: Put “Xs” in the table below if the par±cle is present in that loca±on Start of the experiment Particle Is it outside the cell? Is it inside the cell? IKI starch glucose End of the experiment Particle Is it outside the cell? Is it inside the cell? IKI \ glucose Conclusion: 1. Which par±cles were able to cross the cell membrane? Which par±cles were NOT able to cross the cell membrane? How do you know (cite evidence from our observa±ons)? This study source was downloaded by 100000852590013 from CourseHero.com on 10-13-2023 22:50:22 GMT -05:00

https://www.coursehero.com/file/212378090/osmosis-lab-final-1docx/ 2. How do par±cles naturally move? You cannot say that par±cles always move from outside to inside or inside to outside – what is the rule demonstrated here? 3. For the par±cles that moved, did they ALL move to the other side? What is the rule here? Lab 1: Effects of Osmotic Potential Differences Across a Membrane Materials:  6 ~ 20 cm strips of dialysis tubing  0.0 M sucrose solution – distilled water  0.2 M sucrose solution  0.4 M sucrose solution  0.6 M sucrose solution  0.8 M sucrose solution  1.0 M sucrose solution  Distilled water  Timer  Digital scale  6 clear plastic cups To make sucrose solutions: Add the number of grams of sucrose according to the table below and fill to the 100mL line with distilled water. You may need to heat the water to get the higher concentrations of sucrose to dissolve. You’ll use this for BOTH labs. Molarity Grams sucrose per 100 mL solution 0.2 6.8 0.4 13.7 0.6 20.5 0.8 27.4 1 34.2 Lab 1 Hypothesis : Think about what your variables are and construct a hypothesis predicting the relationship between them. ________________________________________________________________________________________ ________________________________________________________________________________________ Procedure: You will conduct the experiment using the virtual lab here (don’t worry about recording this data, you’ll be provided data): https://video.esc4.net/video/assets/Science/Biology/Gateway%20Resources/cell%20homeostasi s %20virtual%20lab%20-%20activity/index.html Answer the questions after the virtual lab here. 1. Which dialysis tubes had li²le or no change in mass a³er a 24-hour period? 2. Why was pure water used as a control group? This study source was downloaded by 100000852590013 from CourseHero.com on 10-13-2023 22:50:22 GMT -05:00

https://www.coursehero.com/file/212378090/osmosis-lab-final-1docx/ 3. Why didn’t the mass of dialysis tubes “A” and “C” change over the 24-hour ±me frame? Data Concentration of sucrose solution inside dialysis bags (outside always dH2O) 0.0 M (water) 0.2 M 0.4 M 0.6 M 0.8 M 1.0 M Class mean 1.80% 7.8% 13.8% 18.9% 23.4% 26.2% Class standard deviation 8.0% 8.9% 9.9% 12.2% 14.6% 7.6% Class sample size (n) 27 27 27 27 27 24 Graph the above data (remember what your variables are and where they go!) and paste your graph below: Analysis Ques±ons 1. What is the general trend that you see between variables in the graph? Why does this occur? 2. Iden±fy a case where solu±ons where isotonic to each other in the above data. Also iden±fy one case where a solu±on is hypertonic (be clear which solu±on you are referring to). 3. Iden±fy the general rule for predic±ng water movement if the solute concentra±ons on both sides are known (and the solute is impermeable). This study source was downloaded by 100000852590013 from CourseHero.com on 10-13-2023 22:50:22 GMT -05:00 https://www.coursehero.com/file/212378090/osmosis-lab-final-1docx/ 4. These bags all spent the same amount of ±me in the dis±lled water (20 mins). So you could divide the % changes in

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