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Hands On Lab 2: Cells and Membrane Transport (3 Activities) Submission instructions
• Type your answers and copy all pictures directly into this Word document. Submit it via the blackboard submission link in Word format (docx).
Introduction: Cells are the basic structural and functional units of life. Your entire body is composed of cells and the substances produced by them. Each type of cell you possess has a unique structure based on its overall function, but they all share a set of common organelles that fulfill the basic needs every cell has. We will look at each of these organelles, identify them, and define their functions. One of the universal activities within the body is the movement of substances into and out of cells. Gases, nutrients, wastes, chemicals, and water must all be transported in a controlled manner for cells to maintain homeostasis. For example, if a cell contains too much or too little salt, then it will die. The plasma membrane is the major regulator of cellular transport. In this lab you will demonstrate the two simplest transport mechanisms used by the plasma membrane, diffusion and osmosis. Watch This: This video on tonicity is particularly helpful and clear on explaining this concept that many find a bit tricky. It will be quite helpful when working on activity 3 in this lab. Khan Academy Tonicity (opens in new window: 6min:30sec)
Activity 1: Cellular Structure Complete the table by identifying each part of the cell (diagram on next page) and give the function of each. Both columns must be correct for credit.
Structure Function
1. Goigi Apparatus
2.Cilia
2.
3. Peroxisome
4. Nucleus
5. Nucleolus
6. Nuclear Envelope
7. Ribosome
8. Smooth ER
9. Centrrioles
10. Lysosome
11. Plasma Membrane
12. Mitochondrion
13. Microvilli
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Activity 1 Conclusion Questions All parts of the question must be correct for credit. 14. Many of what small organelles give #7 it’s studded appearance AND what is the
function of these?
15. What organelle is not visible on the cell above because in humans it is present only on sperm?
16. What are the loose strands of DNA with associated proteins found in the nucleus AND what form do these strands coil tightly into as the cell begins to divide?
17. Name the 3 types of proteins that make up the cytoskeleton in order from largest to smallest.
18. A double-layer of what molecules are the main component of #11? Membrane Transport Pre-Activity Questions 19. To facilitate transport, the plasma membrane of a cell is selectively permeable.
Define selective permeability.
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20. Define solution and give examples of the two major components of solutions.
21. Watch this 3 minute video about concentration gradients (link opens in new window). How would you describe a concentration gradient?
22. Define diffusion
23. Define osmosis
24-27. Compare and contrast diffusion and osmosis. Give at least 2 differences and 2 similarities (1pt. for each difference and 1pt for each similarity).
Activity 2: Diffusion In this activity, you will observe a substance diffusing through a selectively permeable membrane. As evidence of diffusion, we will use iodine, an indicator that turns blue- black the presence of starch. Materials
• 2-cup clear glass container o Size does not have to be exact,
but it should be taller than it is wide
o Drinking glasses or measuring cups work fine.
• 1 sandwich size resealable bag o The cheaper the bag, the better
this experiment will work • ~10 drops liquid Iodine
o Warning: Handle with care, toxic if ingested and can stain!
o Can be obtained in any drugstore
▪ Do NOT purchase colorless iodine! It will not work. Iodine should be brownish-yellow in color.
• ~2 tablespoons Cornstarch • Water • Camera
Procedure 1. Fill the glass container with 200 mL (~1 cup) of water and add 10 drops of iodine 2. Place 2-4 tablespoons of cornstarch in a plastic bag and add 100 mL of water. 3. Carefully close the bag and gently squeeze to mix the cornstarch and water.
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4. Gently place the bag into the container so that the cornstarch solution is submerged in the iodine solution.
5. Gather data a. Take a picture at the start (0min) and end of your experiment (60min). Post
these pictures in the results section. b. In the provided data table, record the starting color of the solution in the
beaker and bag, then observe and record color changes every 15 minutes for 1 hour.
Results 28. 0min Picture
29. 60min Picture
30. Data Table
Solution 0 min 15min 30min 45min 60min
Color in Container
Color in Bag
Activity 2 Conclusion Questions 31. Based on your observations, which substance moved, the iodine or the cornstarch? How can you tell? 32. What would happen if you did an experiment in which the iodine solution was in the plastic bag and the cornstarch solution was in the beaker?
Activity 3: Osmosis In this activity, you will observe osmosis through a selectively permeable membrane. Osmosis is easily observed in plants, as the osmotic pressure of the water is what provides support (this is why plants wilt when they need water). In this lab you will observe the effect of osmosis using a very familiar plant, the potato. Materials
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• 2 clear glass containers o Size does not have to be exact, but shallow bowls work best
• 1 Potato
• Salt
• Water
• Camera Procedure 1. Label or mark your containers #1 and #2—Any method works, as long as you can
tell them apart. 2. In container 1, mix 15 m (one tablespoon) of salt with 100 ml (~1/2 cup) of water and
stir until the salt is completely dissolved. 3. In container 2, fill with 100ml (~1/2 cup) of pure water. 4. Cut 2 strips of potato about the size of a French fry. They should be no thicker than
0.5 cm (~⅓ in). Make sure to remove all of the skin from the potato. 5. Gather preliminary data
c. Take a picture of both potato strips at the start (0min) of your experiment. Post this picture in the results section.
d. Examine each strip and record your observations of the firmness of the strips in the provided data table
6. Place one of the strips in container #1 (salt water) and the other strip in the container #2 (pure water). Make sure that both potato strips are completely submerged.
7. Leave the strips in the water for 60 minutes. 8. Gather Results
e. Take a picture of both potato strips at the end (60min) of your experiment. Post this picture in the results section.
f. Examine each strip and record your observations of the firmness of the strips in the provided data table
33. 0min Picture
34. 60min Picture
35. Data Table
Container Firmness @ 0 min Firmness @ 60min
1 (salt water)
2 (Pure water)
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Activity 3 Conclusion Questions 36. This experiment showed osmosis. Based on your results would you classify the salt water as hypertonic or hypotonic? Why? 37. This experiment showed osmosis. Based on your results would you classify the pure water as hypertonic or hypotonic? Why? 38-46: Hypothetically, use red blood cells to explain osmosis and states of tonicity. Red blood cells naturally are approximately 0.9% salt in content. We introduced red blood cells to the following solutions:
A. 100% water B. 0.9% saline C. 10% saline
Match solutions A, B, or C with the criteria (each letter used 3x):
Solution Type
Solution A, B, or C
Net Water Movement
Solution A, B, or C
Cell Change Solution A, B, or C
Hypertonic 38. Into Cell 41. No Change 44.
Hypotonic 39. No Water Movement
42. Crenation 45.
Isotonic 40. Out Of Cell 43. Swelling/ Lysis
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Hands On Lab 2: Cells and Membrane Transport (3 Activities)
Introduction:
Activity 1: Cellular Structure
Activity 1 Conclusion Questions
Membrane Transport Pre-Activity Questions
Activity 2: Diffusion
Materials
Procedure
Results
Activity 2 Conclusion Questions
Activity 3: Osmosis
Materials
Procedure
Activity 3 Conclusion Questions
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