Science Biology Unit 04 Exemplar Lesson 02: Homeostasis and Membrane Transport

Transcription

1 Science Unit 04 Exemplar Lesson 02: Homeostasis and Membrane Transport Science Unit: 04 Lesson: 02 Suggested Duration: 7 days This lesson is one approach to teaching the State Standards associated with this unit. Districts are encouraged to customize this lesson by supplementing with district-approved resources, materials, and activities to best meet the needs of learners. The duration for this lesson is only a recommendation, and districts may modify the time frame to meet students needs. To better understand how your district may be implementing CSCOPE lessons, please contact your child s teacher. (For your convenience, please find linked the TEA Commissioner s List of State Board of Education Approved Instructional Resources and Midcycle State Adopted Instructional Materials.) Lesson Synopsis In this lesson, students investigate various types of membrane transport in cells and how these processes help maintain homeostasis in the cell. TEKS The Texas Essential Knowledge and Skills (TEKS) listed below are the standards adopted by the State Board of Education, which are required by Texas law. Any standard that has a strike-through (e.g. sample phrase) indicates that portion of the standard is taught in a previous or subsequent unit. The TEKS are available on the Texas Education Agency website at B.4 Science concepts. The student knows that cells are the basic structures of all living things with specialized parts that perform specific functions and that viruses are different from cells. The student is expected to: B.4B Investigate and explain cellular processes, including homeostasis, energy conversions, transport of molecules, and synthesis of new molecules. Scientific Process TEKS Readiness Standard B.11 Science concepts. The student knows that biological systems work to achieve and maintain balance. The student is expected to: B.11A Describe the role of internal feedback mechanisms in the maintenance of homeostasis. Supporting Standard B.1 Scientific processes. The student, for at least 40% of instructional time, conducts laboratory and field investigations using safe, environmentally appropriate, and ethical practices. The student is expected to: B.1A Demonstrate safe practices during laboratory and field investigations. B.1B Demonstrate an understanding of the use and conservation of resources and the proper disposal or recycling of materials. B.2 Scientific processes. The student uses scientific methods and equipment during laboratory and field investigations. The student is expected to: B.2E B.2F Plan and implement descriptive, comparative, and experimental investigations, including asking questions, formulating testable hypotheses, and selecting equipment and technology. Collect and organize qualitative and quantitative data and make measurements with accuracy and precision using tools such as calculators, spreadsheet software, data-collecting probes, computers, standard laboratory glassware, microscopes, various prepared slides, stereoscopes, metric rulers, electronic balances, gel electrophoresis apparatuses, micropipettors, hand lenses, Celsius thermometers, hot plates, lab notebooks or journals, timing devices, cameras, Petri dishes, lab incubators, dissection equipment, meter sticks, and models, diagrams, or samples of biological specimens or structures. B.2G Analyze, evaluate, make inferences, and predict trends from data. B.2H Communicate valid conclusions supported by the data through methods such as lab reports, labeled drawings, graphic organizers, journals, summaries, oral reports, and technology-based reports. GETTING READY FOR INSTRUCTION Performance Indicators High School Science Unit 04 PI 02 Using a model of a cell membrane, demonstrate examples of diffusion, osmosis, and active transport. For each example, explain the movement of molecules in terms of homeostasis. Standard(s): B.2E, B.2H, B.4B, B.11A ELPS ELPS.c.1E, ELPS.c.3G, ELPS.c.5G Key Understandings Different substances move across the cell membrane by diffusion, osmosis, or active transport to maintain homeostasis. What are diffusion and osmosis? Last Updated 04/29/2013 page 1 of 31

2 What is active transport and what are some examples? How do passive and active transport help a cell maintain homeostasis? Science Unit: 04 Lesson: 02 Suggested Duration: 7 days Vocabulary of Instruction diffusion osmosis passive transport endocytosis active transport homeostasis ion/protein pump exocytosis semi-permeable membrane/ selectively permeable membrane Materials 1 g corn or potato starch per 99 ml 1% starch solution (see Advance Preparation, ml per group) 1 dialysis tubing (about 40 cm per group) 10% saline solution (, see Advance Preparation, 1 2 drops per group) beakers (250 ml,3 per group) bottle of perfume or body spray (1 per teacher) calculators (2 per group) computer access (see Advance Preparation, 1 per group, see Advance Preparation) Optional corn syrup (approximately 200 ml per group) cover slips (1 per group) eggs (chicken, 2 per group) Elodea leaves (1 leaf per group) food coloring (any color, 1 bottle per teacher) forceps (1 per group) graduated cylinder (50 ml, 1 per group) grease pencil or marker (1 per group) Iodine-Potassium Iodide Solution (IKI) (*order from supply company, 0.2 ml per group) lab aprons (1 per student) large graphic of cell membrane (see Advance Preparation1 per teacher) measuring tape (1 per group) microscope slides (1 per group) microscopes (1 per group) mm ruler (1 per group) models or graphic of a cell membrane (see Advance Preparation, 1 per group) movie editing software (see Advance Preparation, 1 per group) paper towels pipette (1 per group) plastic wrap (2 medium size pieces per group) safety goggles (1 per student) string (12 in per group) timing device (1 per group) triple beam balance or digital scale (1 per group) triple beam balance or electronic scale (4 to share between groups) video camera or device that can record video (see Advance Preparation, 1 per group) vinegar (approximately 400 ml per group) water Attachments All attachments associated with this lesson are referenced in the body of the lesson. Due to considerations for grading or student assessment, attachments that are connected with Performance Indicators or serve as answer keys are available in the district site and are not accessible on the public website. Handout: Osmosis in Eggs (1 per student) Teacher Resource: Osmosis in Eggs KEY Handout: Cell Membrane Research (1 per student) Teacher Resource: Cell Membrane Research KEY Handout: Observing Osmosis in Elodea (1 per student) Teacher Resource: Observing Osmosis in Elodea KEY Handout: Cell Transport and Homeostasis Key Terms (1 per student) Teacher Resource: PowerPoint: Cell Transport and Homeostasis Terms KEY Handout: Osmosis Experimental Design Lab (1 per student) Teacher Resource: Osmosis Experimental Design Lab KEY Handout: Membrane Transport Movie Project PI (1 per student) Last Updated 04/29/2013 page 2 of 31

3 Teacher Resource: Performance Indicator Instructions KEY Science Unit: 04 Lesson: 02 Suggested Duration: 7 days Resources None Identified Advance Preparation 1. Prior to Day 1, locate a large graphic of the cell membrane to either print and display on a poster board or display via a projection system in the classroom. 2. Prior to Day 1, arrange for access to student computers with Internet access. 3. Prior to Day 2, prepare the saline (salt) solution for the osmosis in Elodea lab. Prepare a 10% solution by mixing 10 g NaCl with 90 ml water. If you will need more than 90 ml, double or triple the recipe to make larger amounts. 4. Prior to Day 3, review the Teacher Resource: PowerPoint: Cell Transport and Homeostasis Key Terms to insert any additional animations or graphics that may help your students understand the types of transport. 5. Prior to Day 5, prepare a 1% starch solution by adding 1 g of corn or potato starch to 99 ml of cold water. Bring the mixture to a boil, and then allow it to cool. You can do this in a microwave. Multiply this recipe to make larger amounts. You will need approximately ml for every group. 6. Prior to Day 5, cut the dialysis tubing into lengths of cm. You may also wish to pre cut 6 inch pieces of string. If you do not want to use string, you can also give students longer lengths of dialysis tubing, and they can tie the tubing itself. 7. Prior to Day 6, obtain cell membrane models or print cell membrane graphics for each group of 3 4 students to use during their Performance Indicator. Arrange for access to video cameras or other technology (smart phones) for groups to record their assessment product. Consider providing access computers (1 per group) and movie editing software, such as imovie or Movie Maker (1 per group). 8. Prepare attachment(s) as necessary. Background Information This lesson bundles student expectations that address cell structures and functions and the transport of molecules into and out of the cell. In the previous lesson, students identified cell structures and cell types. In this lesson, they will investigate homeostasis and the movement of molecules in relation to the cell. This lesson provides a knowledge base crucial for subsequent units. After this unit, students will learn about the specific cell structures and processes that operate in the context of genetics, evolution, classification, viruses and bacteria, plants, and body systems. STAAR Notes: The transport of molecules is part of student expectation B.4B, which is a Readiness Standard on the STAAR Assessment. Transport of molecules will not be directly taught again before the test. The other student expectation in this lesson, B.11A, is a Supporting Standard. Other than the content on transport of molecules, all student expectations from this unit are reinforced in subsequent units before the test. INSTRUCTIONAL PROCEDURES Instructional Procedures ENGAGE Homeostasis and Membrane Transport Teacher Demo: 1. Spray perfume (or some chemical substance) into the air. (See the Safety Notes.). Tell students to imagine the perfume molecules. Have students describe what is happening to the molecules in space. (They are randomly bumping against each other and slowly spreading throughout the room.) Ask: What are some other examples of odors spreading through a space? Student answers will vary based on their experiences, but may include: smelling foods from their kitchen in another room, smelling a person s lotion across the room as they put it on, or smelling fragrances from flowers in a garden. 2. Add several drops of food coloring to a beaker of water in front of students. Tell students to imagine the dye molecules. Have students describe what is happening to the molecules in the water. (They are randomly bumping against each other and are slowly spreading throughout the water. Eventually the color will be even throughout the beaker). Ask: What would happen if I stirred the water and food coloring? Why? The food coloring would spread out more quickly because the motion of the molecules would be increased. What would happen if I heated the water and food coloring? Why? The food coloring would spread out more quickly because the motion of the molecules would be increased. Notes for Teacher NOTE: 1 Day = 50 minutes Suggested Day 1 Materials: bottle of perfume or body spray (1 per teacher) beaker of water (500 ml, filled ¾ full, 1 per teacher) food coloring (any color, 1 bottle per teacher) Safety Notes: Ensure you use a perfume/body spray that will not cause a reaction with any of your students. Some students are sensitive to strong odors. If this is the case, consider doing only the food coloring demonstration and/or finding another demonstration that does not involve odor, such as opening a bag of freshly popped popcorn. Misconception: Students may be unaware that cells respond to internal and environmental conditions to maintain balance. 3. Stress to students that the perfume and dye molecules are moving from areas of higher concentration to areas of lower concentration. This is called moving down their Last Updated 04/29/2013 page 3 of 31

4 concentration gradient. Explain to students that both demonstrations are examples of diffusion, and cells use this process as well. Science Unit: 04 Lesson: 02 Suggested Duration: 7 days 4. Ask students to think about and answer the following questions. Encourage students to relate what is happening at the cellular level. Remember what is true of the organism is true of its cells. Ask: What happens to your thirst level when you sweat a lot? You get thirsty as you sweat because your cells are losing water. Why does your body sweat? To help it stay cool (Introduce the concept of homeostasis at this point.), the body is helping maintain homeostasis (correct body temperature) by sweating. What happens to plants (how do they appear) when you water them? When you don t water them? Watering plants makes them stand up, and not watering plants, makes them limp. In either case, water is moving into or out of the plant cells. What part of the cell is allowing water to move into or out of the cell in both of these examples? (The cell membrane) 5. Inform students that just as perfume molecules move through the air or dye molecules move through water, all kinds of molecules (oxygen, food, waste, etc.) move down their concentration gradient as they move across the cell membrane in order to maintain homeostasis in our cells. Ask: Why is maintaining homeostasis important to cells? Answers will vary based on student background knowledge, but students should come to the conclusion that cells would not be able to function properly if they were not at homeostasis. 6. Discuss with students how a building like the school is able to maintain a fairly constant temperature on a hot day. The thermostat is set to a desirable temperature. It then monitors the temperature, and if the room is too warm, it triggers the AC to start and then stop when the desired temperature is reached. In this way, the thermostat helps maintain the homeostasis of the room. This system is called a feedback loop. Ask: How might this apply to an organism and its cells? Student answers will vary, but guide them toward the concept that a similar feedback loop is observed at the organism level and on the cellular level. Triggers will signal an organism or cell when balances are off, and the organism or cell will respond to get itself back to homeostasis. EXPLORE Homeostasis and Membrane Transport 1. Divide the class into lab groups of two. Distribute the Handout: Osmosis in Eggs to each student. 2. Instruct students that they will complete only the Day 1 portion of this activity today. On Day 2 of this lesson, they will continue with the Day 2 portion, and on Day 3 of this lesson, they will finish by completing the Day 3 portion. 3. Review safety precautions with students (see Safety Notes). 4. When students have completed Day 1 of the Osmosis in Eggs activity, they will remain with their lab partner and complete research on cell membranes using the Handout: Cell Membrane Research. 5. When students have completed the cell membrane tutorial research, instruct them to write a 1 2 paragraph summary about the cell membrane in their science notebooks. Summaries should include the following: A description and brief sketch of the lipid bilayer of the cell membrane The function of the cell membrane What molecules can easily diffuse through the membrane? How larger molecules get through the membrane 6. End Day 1 with a brief discussion about the cell membrane. Display a large graphic of the cell membrane, and review the structure and function of the cell membrane with students. Be sure to discuss the concept of selective permeability. 7. Begin Day 2 with Osmosis in Eggs Day 2 procedures. Again, review safety precautions. 8. When students have completed Day 2 of the Osmosis in Eggs activity, they will remain in their lab groups. Distribute the Handout: Observing Osmosis in Elodea. Suggested Day Materials: beakers (250 ml, 2 per group) eggs (chicken, 2 per group triple beam balance or digital scale (1 per group) measuring tape (1 per group) vinegar (approximately 400 ml per group) plastic wrap (2 medium size pieces per group) water (approximately 200 ml per group) corn syrup (approximately 200 ml per group) grease pencil or marker (1 per group) timing device (1 per group) calculators (2 per group) large graphic of cell membrane (see Advance Preparation1 per teacher) microscopes (1 per group) Elodea leaves (1 leaf per group) water (1 2 large beakers per class to share) 10% saline solution (, see Advance Preparation, 1 2 drops per group) 10 g NaCl (salt) 90 ml water microscope slides (1 per group) cover slips (1 per group) forceps (1 per group) pipette (1 per group) paper towels (several per group) Last Updated 04/29/2013 page 4 of 31

5 9. Allow students to review the lab procedures, and clarify any procedures if needed. Instruct students on the proper disposal of lab materials. 10. When students have completed the activity, conduct a debrief discussion of the Observing Osmosis in Elodea activity. Use the analysis questions to guide the discussion. 11. Begin Day 3 with the conclusion of the Osmosis in Eggs activity. Remind students of safety precautions. 12. When students have completed the activity, facilitate a class discussion in which students reflect on the following questions: Ask: Why did the egg in container 1 (water) continue to become heavier/larger? It continued to take in water from its surroundings because there was less water inside the egg. Therefore, water diffused into the egg trying to reach equilibrium. Why did the egg in container 2 become lighter/smaller? Water inside the egg moved out into the corn syrup because there was less water outside the egg. Water diffused out of the egg, trying to reach equilibrium. Why does the egg from container 2 have a shriveled appearance? Because it lost water. What is a good definition for diffusion? Student answers may vary slightly, but should include the concept that diffusion is the movement of particles from an area of high concentration to an area of low concentration, along its concentration gradient until equilibrium is reached. What is a good definition for osmosis? Student answers may vary slightly, but should include that osmosis is the diffusion of water. Science Unit: 04 Lesson: 02 Suggested Duration: 7 days safety goggles (1 per student) lab aprons (1 per student) Attachments: Handout: Osmosis in Eggs (1 per student) Teacher Resource: Osmosis in Eggs KEY Handout: Cell Membrane Research (1 per student) Teacher Resource: Cell Membrane Research KEY Handout: Observing Osmosis in Elodea (1 per student) Teacher Resource: Observing Osmosis in Elodea KEY Safety Notes: Students should wear lab aprons and safety goggles when working with the eggs, vinegar, and glassware. Also, eggs may carry salmonella, so students should wash hands very well at the conclusion of the lab setup. Students should also wear lab aprons and safety goggles during the Observing Osmosis in Elodea activity. Instructional Notes: The Osmosis In Eggs lab spans three days. Day 1 will be completed today, Day 2 will be completed tomorrow, and Day 3 will be completed on Day 3 of this lesson. On Days 1 and 2, students will also complete other activities after the osmosis in eggs portion is complete. If computer access is limited, groups can be combined for the cell membrane research activity. Science Notebooks: At the completion of the Cell Membrane Research activity, students should write a 1 2 paragraph summary about the cell membrane in their science notebooks. EXPLAIN Homeostasis and Membrane Transport 1. Distribute the Handout: Cell Transport and Homeostasis Key Terms to each student. 2. Use the Teacher Resource: PowerPoint: Cell Transport and Homeostasis Terms KEY, discussing slides in order to help students complete their handout (see Advance Preparation). 3. Include the following questions in your discussion: What are diffusion and osmosis? What is active transport and what are some examples? How do passive and active transport help a cell maintain homeostasis? 4. Use the presentation as a guide for your discussion, first asking students about each term and then working with students to develop a more complete definition. Suggested Day 3 (continued) Attachments: Handout: Cell Transport and Homeostasis Key Terms (1 per student) Teacher Resource: PowerPoint: Cell Transport and Homeostasis Terms KEY Instructional Notes: Use the PowerPoint resource as a guide for class discussion, rather than just supplying students with all of the definitions. Draw upon student experiences from Days 1 3 to help facilitate a good discussion. Review the PowerPoint and slide notes before Day 3 to insert any additional animations or graphics that you may wish to use to help students understand the types of transport. Check For Understanding: At the conclusion of this discussion and filling out their handout, students should be able to answer the following questions: What are diffusion and osmosis? What is active transport and what are some examples? How do passive and active transport help a cell maintain homeostasis? Last Updated 04/29/2013 page 5 of 31

6 Misconception: Science Unit: 04 Lesson: 02 Suggested Duration: 7 days Students may be unaware that cells respond to internal and environmental conditions to maintain balance. STAAR Notes: The transport of molecules is part of student expectation B.4B, which is a Readiness Standard on the STAAR Assessment. Transport of molecules will not be directly taught again before the test. The other student expectation introduced in this lesson, B.11A, is a Supporting Standards. ELABORATE Homeostasis and Membrane Transport Suggested Days 4 and 5 1. Divide the class into small groups of 2 3 students. 2. Distribute the Handout: Osmosis Experimental Design Lab to each student. Review the background information and expectations with students (Refer to the Teacher Resource: Osmosis Experimental Design Lab KEY, and answer any questions students may have.). 3. Remind students that their lab experimental design/procedures must to be approved by you before they begin their experiment. 4. Inform students they will complete the pre-lab questions and design their experiment on Day 4, and they will conduct their experiment and analysis on Day Monitor and assist students as they complete their planning and implementation of their experimental labs. Materials beakers (250 ml,3 per group) 1% starch solution (see Advance Preparation, ml per group) 1 g corn or potato starch per 99 ml 1 dialysis tubing (about 40 cm per group) string (12 in per group) Iodine-Potassium Iodide Solution (IKI) (*order from supply company, 0.2 ml per group) graduated cylinder (50 ml, 1 per group) triple beam balance or electronic scale (4 to share between groups) mm ruler (1 per group) paper towels (several per group) Attachments: Handout: Osmosis Experimental Design Lab (1 per student) Teacher Resource: Osmosis Experimental Design Lab KEY Instructional Notes: Prepare the starch solution and dialysis tubing prior to Day 5, following the instructions in the Advance Preparation section. Additional instructional notes can be found in the Teacher Resource: Osmosis Experimental Design Lab KEY document. EVALUATE Performance Indicator Homeostasis and Membrane Transport Suggested Days 6 and 7 High School Science Unit 04 PI 02 Using a model of a cell membrane, demonstrate examples of diffusion, osmosis, and active transport. For each example, explain the movement of molecules in terms of homeostasis. Standard(s): B.2E, B.2H, B.4B, B.11A ELPS ELPS.c.1E, ELPS.c.3G, ELPS.c.5G 1. Refer to the Teacher Resource: Performance Indicator Instructions KEY and Handout: Membrane Transport Movie Project PI (1 per student) for information on administering the assessment. Materials: models or graphic of a cell membrane (see Advance Preparation, 1 per group) video camera or device that can record video (see Advance Preparation, 1 per group) computer access (see Advance Preparation, 1 per group, see Advance Preparation) Optional movie editing software (see Advance Preparation, 1 per group) Attachments: Handout: Membrane Transport Movie Project PI (1 per student) Teacher Resource: Performance Indicator Instructions KEY Last Updated 04/29/2013 page 6 of 31

7 Osmosis in Eggs Objective: Observe the effects on an egg placed in vinegar, water, and corn syrup. Relate this to osmosis in cells. Materials: 250 ml beakers (2) chicken eggs (2) triple beam balance or digital scale safety goggles lab aprons vinegar (approximately 400 ml) plastic wrap (2 medium size pieces) water (approximately 200 ml) corn syrup (approximately 200 ml) grease pencil or marker measuring tape Day I Procedure: 1. Obtain two 250 ml beakers. Label one beaker #1 and the other beaker #2. 2. Obtain two chicken eggs from your instructor. 3. Use a triple-beam balance or digital scale to measure the mass of each egg. Record the mass in the data table provided. 4. Use a measuring tape to measure the circumference of each egg in cm (around the widest part). Record the circumference in the data table. 5. Place one egg in beaker #1 and one egg in beaker #2. Fill the beaker with enough vinegar to cover the egg. Use cling wrap to cover the top of the beaker. 6. Leave the eggs overnight. 7. Wash your hands thoroughly, and then answer the questions below. 2012, TESCCC 08/16/12 page 1 of 4

8 Day I Questions: 1. Why are you placing the eggs in vinegar? 2. What do you think will happen to the eggs overnight? Day II Procedure: 1. Remove both eggs from their vinegar and wash. Rub the egg gently to remove as much of the shell as possible. If a small portion of the shell is stuck, this is okay. 2. Gently dry each egg, and measure its mass. Record the mass in the data table. 3. Use a measuring tape to measure the circumference of each egg. 4. Empty the vinegar from beaker #1, as directed by your instructor. Fill beaker #1 with enough water to cover the egg. Place egg #1 back into beaker #1. 5. Empty the vinegar from beaker #2, as directed by your instructor. Fill beaker #2 with enough corn syrup to cover the egg. Place egg #2 back into beaker #2. 6. Wash your hands thoroughly, and then answer the questions below. Day II Questions: 1. What happened to the mass of the eggs? Why do you think this happened? 2. What do you think will happen to the egg in beaker #1? 3. What do you think will happen to the egg in beaker #2? 2012, TESCCC 08/16/12 page 2 of 4

9 Day III Procedure: 1. Remove the egg from beaker #1, dry it, and measure its mass and circumference. Record the measurements in the data table. 2. Remove the egg from beaker #2, rinse the corn syrup off of the egg, dry it, and measure its mass and circumference. Record the measurements in the data table. 3. Dispose of all materials, following your teacher s instructions. 4. Clean the beakers and your lab area. Wash your hands thoroughly, and then answer the questions below. Day III Questions: 1. What happened to the egg in beaker #1? Why do you think this happened? 2. What happened to the egg in beaker #2? Why do you think this happened? 3. The title of this lab is Osmosis in Eggs. Based on that title and what you observed in the eggs, what do you think osmosis means? 2012, TESCCC 08/16/12 page 3 of 4

10 Data Tables: Beaker #1 Day Mass (g) Circumference (cm) 1 (egg put into vinegar) 2 (egg put into water) 3 Beaker #2 Day Mass (g) Circumference (cm) 1 (egg put into vinegar) 2 (egg put into corn syrup) , TESCCC 08/16/12 page 4 of 4

11 Osmosis in Eggs KEY Day I Questions: 1. Why are you placing the eggs in vinegar? What do you think will happen to the egg overnight? Student answers will vary, but they may hypothesize that the vinegar will help remove the egg s shell based on seeing it bubble or based on previous experiences. Day II Questions: 2. What happened to the mass of the eggs? Why do you think this happened? The mass and circumference of the eggs increases. Student answers, as to why this happened, may vary but the correct answer is: because vinegar has more water than the inside of the egg, so water moves into the egg. Accept student answers that show thought and effort. 3. What do you think will happen to the egg in beaker #1? Student answers will vary. 4. What do you think will happen to the egg in beaker #2? Student answers will vary. Day III Questions: 5. What happened to the egg in beaker #1? Why do you think this happened? The egg put into water will continue to increase in mass and circumference. Student answers, as to why this happened, may vary but the correct answer is: there was more water outside the egg than inside the egg (and less solute outside than inside); therefore, water from the beaker moved into the egg through its membrane. Accept student answers that show thought and effort. 6. What happened to the egg in beaker #2? Why do you think this happened? The egg in the corn syrup decreases in mass and circumference. It also appears shriveled. Student answers, as to why this happened, may vary but the correct answer is: there was more water inside the egg than in the corn syrup; therefore, water from the egg moved into the corn syrup. 7. The title of this lab is Osmosis in Eggs. Based on that title and what you observed in the eggs, what do you think osmosis means? Student answers will vary but should involve something to do with the movement of liquid or water across a membrane. 2012, TESCCC 08/16/12 page 1 of 2

12 Data Tables: Beaker #1 Day Mass (g) Circumference (cm) 1 (egg put into vinegar) 2 (egg put into water) Will vary depending upon the egg Mass will increase. Will vary depending upon the egg Circumference will increase. 3 Mass will increase again. Circumference will increase again. Beaker #2 Day Mass (g) Circumference (cm) 1 (egg put into vinegar) 2 (egg put into corn syrup) Will vary depending upon the egg Mass will increase. Will vary depending upon the egg Circumference will increase. 3 Mass will decrease. Circumference will decrease. 2012, TESCCC 08/16/12 page 2 of 2

13 Cell Membrane Research Objective: Complete cell membrane research to gain a better understanding of the structure and function of the cell membrane. Instructions: Use resources provided by your teacher to answer the following questions: 1. Of what is the cell membrane composed? 2. What types of molecules go through the cell membrane easily? 3. What types of molecules need more help to get through the cell membrane? What helps them get through? 4. What are the two parts to the phospholipid bilayer of the cell membrane, and how are they arranged? 5. What is the purpose of the fibrous proteins in the cell membrane? 2012, TESCCC 04/19/13 page 1 of 2

14 6. What is the function of channel proteins in the cell membrane? 7. In which type of cell will you find cholesterol molecules in the cell membrane? What is their function? 8. The cell membrane is said to be selectively permeable. What does this mean? (You may need to use additional resources to determine the answer to this question.) Science Notebook Writing Activity: Once the questions above have been completed, write a 1 2 paragraph summary about the cell membrane in your science notebook. It should include the following information: a. Description and brief sketch of the lipid bilayer of the cell membrane b. Function of the cell membrane c. What molecules can easily diffuse through the membrane, and how larger molecules get through the membrane? 2012, TESCCC 04/19/13 page 2 of 2

15 Cell Membrane Research KEY Advance Preparation: Locate and preview resources students will be allowed to use to complete their research on cell membranes. You may wish to use an on line tutorial, such as the one located at the following URL: Note: Websites are subject to changes and may have associated links that are neither referenced nor approved by CSCOPE. District personnel are encouraged to preview and vet all websites, resources, and references in accordance with district policy. Objective: Complete cell membrane research to gain a better understanding of the structure and function of the cell membrane. Instructions: Use resources provided by your teacher to answer the following questions: Answer the questions below: 1. Of what is the cell membrane composed? It is composed of lipids and proteins. The framework is a double layer of phospholipids. 2. What types of molecules go through the cell membrane easily? Lipid soluble substances such as oxygen, carbon dioxide, and steroids can get through easily. 3. What types of molecules need more help to get through the cell membrane? What helps them get through? Water-soluble substances, like water, ions, glucose, and amino acids, need the help of various proteins to get through the membrane. 4. What are the two parts to the phospholipid bilayer of the cell membrane, and how are they arranged? The phospholipid bilayer is composed of water-soluble heads and water insoluble tails. The heads make up the outer and interior surface of the membrane, and the tails face each other. (Students may wish to draw a brief sketch.) 5. What is the purpose of the fibrous proteins in the cell membrane? They are receptors for the cell. 6. What is the function of channel proteins in the cell membrane? They transport selected ions across the cell membrane. 2012, TESCCC 04/19/13 page 1 of 2

16 7. In which type of cell will you find cholesterol molecules in the cell membrane? What is their function? Cholesterol is found in the cell membrane of animal cells. They help keep out water and help stabilize the membrane. 8. The cell membrane is said to be selectively permeable. What does this mean? (You may need to use additional resources to determine the answer to this question.) Selectively permeable means it will only let certain things through. Science Notebook Writing Activity: Once the questions above have been completed, write a 1 2 paragraph summary about the cell membrane in your science notebook. It should include the following information: a. Description and brief sketch of the lipid bilayer of the cell membrane b. Function of the cell membrane c. What molecules can easily diffuse through the membrane, and how larger molecules get through the membrane? Check students science notebooks to ensure they have written a complete summary and included a brief sketch of the cell membrane. 2012, TESCCC 04/19/13 page 2 of 2

17 Observing Osmosis in Elodea Objective: Observe the effects of fresh water and salt water on an Elodea leaf to gain a better understanding of osmosis. Materials: microscope (1) blank microscope slide (1) cover slip (1) pipette (2) Elodea (1 small leaf) pond or fresh water (1 2 drops) saline (salt) solution (1 2 drops) paper towels (1 2) Procedure: 1. Obtain a blank microscope slide. Make a wet-mount slide of Elodea using fresh water: a. Place a drop of pond or fresh water onto the center of the slide. b. Place one small Elodea leaf onto the drop. c. Put the cover slip on top of the water by placing the cover slip on the edge of the water at a 45- degree angle and slowly lowering it. If you have any air bubbles, tap the cover slip, and use a paper towel to remove the extra water. 2012, TESCCC 08/16/12 page 1 of 4

18 2. View the wet-mount under the microscope. (Remember to start on the lowest power, and then move to a higher power; the medium objective will likely give you the best view.) Draw at least five cells, and label the cell wall and chloroplasts in the circle below: 3. Remove the cover slip, and use a paper towel to blot off the pond/fresh water. 4. Place a drop of the saline (salt) solution onto the Elodea leaf, and replace the cover slip (using the same technique as before to avoid air bubbles). 5. View the saline wet-mount under the microscope. (Remember to start on the lowest power, and then move to a higher power; the medium objective will likely give you the best view.) Watch what happens to the chloroplasts and cell wall. It may take 1 2 minutes to see the effects of the saline solution. 2012, TESCCC 08/16/12 page 2 of 4

19 6. Draw at least five cells, and label the cell wall and chloroplasts in the circle below: 7. Dispose of all materials as directed by your instructor. Clean your lab area, wash your hands, and then answer the analysis questions. Analysis Questions: 1. Where were the chloroplasts located in the Elodea leaf? 2. Where were the chloroplasts located in the Elodea leaf when the saline (salt) solution was added? 2012, TESCCC 08/16/12 page 3 of 4

20 3. In which structure do you find the most water in a plant cell, such as the Elodea leaf? 4. Describe what happened when you added the saline (salt) solution to the leaf. Why did this happen? 5. In thinking about what you observed in this lab, what would happen to plants on the side of a road if salt was sprayed to melt ice on the road? 6. In thinking about what you observed in this lab, what happens to cells inside salmon when the salmon leave the ocean to swim up river? 2012, TESCCC 08/16/12 page 4 of 4

21 Observing Osmosis in Elodea KEY Analysis Questions: 1. Where were the chloroplasts located in the Elodea leaf under normal conditions? Under normal conditions, the chloroplasts were mostly towards the cell wall, with the central vacuole taking up the center area. 2. Where were the chloroplasts located in the Elodea leaf when the saline (salt) solution was added? When the saline solution was added, the chloroplasts all clumped to the middle of the cell. 3. In which structure do you find the most water in a plant cell, such as the Elodea leaf? The water is mostly in the central vacuole. 4. Describe what happened when you added the saline (salt) solution to the leaf. Why did this happen? The central vacuole shrank, and the chloroplasts all started going towards the center of the cell. The cell wall remained in place. This happened because there was more water inside the cell than outside the cell, so water left the cell to balance out the water inside and outside of the cell. 5. In thinking about what you observed in this lab, what would happen to plants on the side of a road if salt was sprayed to melt ice on the road? Water would flow out of the plant cells, causing them to become wilted. 2012, TESCCC 04/19/13 page 1 of 1

22 Cell Transport and Homeostasis Key Terms Instructions: During the discussion, record a definition for each key term below. Key Term Definition Semi-permeable (selectively permeable) Passive Transport Diffusion Facilitated Diffusion Osmosis Hypotonic Solution 2012, TESCCC 08/16/12 page 1 of 2

23 Key Term Definition Hypertonic Solution Isotonic Solution Active Transport Ion or Protein Pump Endocytosis Exocytosis Homeostasis 2012, TESCCC 08/16/12 page 2 of 2

24 Osmosis Experimental Design Lab Objective: Design an experiment to determine if starch and/or water can cross a simulated cell membrane. Background: Recall from discussions in class that cells use transport methods such as diffusion, osmosis, and active transport to allow substances to cross their cell membrane. Some transport methods are considered passive because they do not require the cell to expend any energy. Other transport methods are active because they require the cell to expend energy. In this lab, you will be investigating osmosis, the diffusion of water across a semi-permeable membrane. Three types of solutions can surround a cell: hypertonic, hypotonic, or isotonic. A hypertonic solution has more dissolved substances than inside the cell. A hypotonic solution has less dissolved substances than inside the cell. An isotonic solution has the same concentration of dissolved substances as inside the cell. The type of solution that surrounds a cell will influence the net flow of water and substances into and out of the cell. Pre-Lab Questions: 1. Diffusion is the net movement of substances from an area of concentration to an area of concentration. 2. A cell s membrane is semi-permeable (also called selectively permeable ). What does this mean? 3. If a cell is in a hypertonic solution, what is the direction of the net flow of water and why? 4. If a cell is in a hypotonic solution, what is the direction of the net flow of water and why? 5. If a cell is in an isotonic solution, what is the direction of the net flow of water and why? Experimental Design: Dialysis tubing is a semi-permeable membrane that acts the same way a cell membrane acts. During this lab, you will be using the dialysis tubing to create small baggies that will represent cells. The fluid inside and outside the baggies will be water and/or starch solution. Question: Which molecule is larger: starch or water? Your experimental design will be written to answer the following questions. In your science notebook, record your prediction for each question: 1. Can water cross the dialysis tubing by osmosis? 2. Can starch cross the dialysis tubing by diffusion? 2012, TESCCC 08/16/12 page 1 of 3

25 3. If there is a higher concentration of water inside the dialysis tubing baggie, what is the net movement of water? 4. If there is a higher concentration of water outside the dialysis tubing baggie, what is the net movement of water? 5. If the concentration of water is the same inside and outside the dialysis tubing baggie, what is the net movement of water? Materials: 250ml beakers (3) 1 dialysis tubing (40 cm) water 1% starch solution ( ml) iodine (0.2 ml) scale or mm ruler paper towels string (12 in) 50 ml graduated cylinder timing device calculators Design an experiment to test your predictions using these materials. Write your experimental design in your science notebooks. Include a diagram showing each beaker/baggie system and what will be inside the beaker and baggie. Describe how and what you will measure during your experiment. Your teacher must approve your experimental design before you can conduct your experiment. When your experimental design is approved, set up your beakers and baggies. Dialysis Tubing Baggies: To make a baggie, soak the tubing in water for about one minute. Then, fold the bottom about 1 cm up, and tie the folded part with a small piece of string to create a bag. Then, open the other end of the tube by rubbing the end between your fingers until the edges are separated. You may want to blow into the bag to open it more and make pouring easier. After pouring the fluid into the baggie, leave some space to allow water to diffuse during your experiment. Next, fold 1 cm of tubing, and tie off the top of the tube with a small piece of string. Finally, rinse your tube and string in fresh water. Squeeze any extra water from the string. You will need to wait approximately 20 minutes to observe the effects of osmosis. While you are waiting, create a data table in your science notebook to record your data. After 20 minutes, collect and record your data. Then, write a summary of your results in your science notebook, and answer the following questions: 1. Were your predictions correct? If they were not correct, why do you think there was a difference between your predictions and what you observed during your experiment? 2. What do your results teach you about the effects of osmosis across a semi-permeable membrane? 2012, TESCCC 08/16/12 page 2 of 3

26 3. Explain what happens to an animal cell that is placed in a hypertonic solution vs. a hypotonic solution. 4. Explain what happens to a plant cell that is placed in a hypertonic solution vs. a hypotonic solution. 5. Discuss the percentage change inside and outside the baggie for your systems. 2012, TESCCC 08/16/12 page 3 of 3

27 Osmosis Experimental Design Lab KEY Teacher Preparation Information (Complete before Day 5): 1. Prepare a 1% starch solution by adding 1 g of corn or potato starch to 99 ml of cold water. Bring the mixture to a boil, and then allow it to cool. You can do this in a microwave. Multiply this recipe to make larger amounts. You will need approximately ml for every lab group of 2 3 students. 2. Cut the dialysis tubing into lengths of cm. You may also wish to pre-cut 6 inch pieces of string. If you do not want to use string, you can also give students longer lengths of dialysis tubing and they can tie the tubing itself. Pre-Lab Questions: 1. Diffusion is the net movement of substances from an area of higher concentration to an area of lower concentration. 2. A cell s membrane is semi-permeable (also called selectively permeable ). What does this mean? It means the cell membrane will only let certain substances through. 3. If a cell is in a hypertonic solution, what is the direction of the net flow of water and why? The water will move out of the cell because there are more dissolved substances outside the cell, which means there is less water outside the cell. The water will move out of the cell to try and reach equilibrium. 4. If a cell is in a hypotonic solution, what is the direction of the net flow of water and why? The water will move into the cell because there are less dissolved substances outside the cell, which means there is more water outside the cell. The water will move into the cell to try and reach equilibrium. 5. If a cell is in an isotonic solution, what is the direction of the net flow of water and why? There is no net flow of water because the amount of dissolved substances and water is the same inside and outside the cell. Experimental Design: Dialysis tubing is a semi-permeable membrane that acts the same way a cell membrane acts. During this lab, you will be using the dialysis tubing to create small baggies that will represent cells. The fluid inside and outside the baggies will be water and/or starch solution. Question: Which molecule is larger: starch or water? Starch is a larger molecule. 2012, TESCCC 08/16/12 page 1 of 3

28 Your experimental design will be written to answer the following questions. In your science notebook, record your prediction for each question: Check student science notebooks for predictions. Answers may vary. 1. Can water cross the dialysis tubing by osmosis? 2. Can starch cross the dialysis tubing by diffusion? 3. If there is a higher concentration of water inside the dialysis tubing baggie, what is the net movement of water? 4. If there is a higher concentration of water outside the dialysis tubing baggie, what is the net movement of water? 5. If the concentration of water is the same inside and outside the dialysis tubing baggie, what is the net movement of water? Materials: 250 ml beakers (3) 1 dialysis tubing (40 cm) water 1% starch solution ( ml) iodine (0.2 ml) scale or mm ruler paper towels string (12 in) 50 ml graduated cylinder timing device calculators Design an experiment to test your predictions using these materials. Write your experimental design in your science notebook. Include a diagram showing each beaker/baggie system and what will be inside the beaker and baggie. Describe how and what you will measure during your experiment. Your experimental design must be approved by your teacher before you can conduct your experiment. When your experimental design is approved, set up your beakers and baggies. Students can measure diffusion of water in a few ways: measure the change in volume of the solution in the tube; measure the change of volume of the solution in the beaker; or measure the change in mass of the solution in the tube. If students choose to use mass, they should make sure the string is as dry as possible when the mass is measured. Dialysis Tubing Baggies: To make a baggie, soak the tubing in water for about one minute. Then, fold the bottom about 1 cm up, and tie the folded part with a small piece of string to create a bag. Then, open the other end of the tube by rubbing the end between your fingers until the edges are separated. You may want to blow into the bag to open it more and make pouring easier. After pouring the fluid into the baggie, leave some space to allow water to diffuse during your experiment. Next, fold 1 cm of tubing, and tie off the top of the tube with a small piece of string. Finally, rinse your tube and string in fresh water. Squeeze any extra water from the string. 2012, TESCCC 08/16/12 page 2 of 3

29 You will need to wait approximately 20 minutes to observe the effects of osmosis. While you are waiting, create a data table in your science notebook to record your data. After 20 minutes, collect and record your data. Then, write a summary of your results in your science notebook and answer the following questions: 1. Were your predictions correct? If they were not correct, why do you think there was a difference between your predictions and what you observed during your experiment? Student answers will vary based on their results. 2. What do your results teach you about the effects of osmosis across a semi-permeable membrane? Students should conclude that water will move from higher to lower concentrations across a semi-permeable membrane. 3. Explain what happens to an animal cell that is placed in a hypertonic solution vs. a hypotonic solution. An animal cell placed in a hypertonic solution will shrink because water will move out of the cell. An animal cell placed in a hypotonic solution will swell and may eventually burst because water will move into the cell. 4. Explain what happens to a plant cell that is placed in a hypertonic solution vs. a hypotonic solution. A plant cell placed in a hypertonic solution will shrink because water will move out of the cell and cause the plant to look wilted. A plant cell placed in a hypotonic solution will swell but will not burst because the cell wall is rigid. 5. Discuss the percentage change inside and outside the baggie for your systems. Student answers will vary based on their results. 2012, TESCCC 08/16/12 page 3 of 3

30 Membrane Transport Movie Project PI Objective: Film a short movie describing types of membrane transport and how they help cells maintain homeostasis. Film Project Requirements: Using the materials/equipment provided by your teacher, write a script; then film, and create a movie including the following: 1. Use a cell membrane model or graphic to explain the following: a. Diffusion b. Osmosis c. At least one example of active transport (protein pump, endocytosis, exocytosis) 2. For each of the transport methods above, give a specific example of how this helps cells maintain homeostasis. 3. Each group member must participate in the creation of the film and appear in the film. 4. You must turn in your film script and film to the teacher. Project Timeline: Day 1: Write script and practice Day 2: Film movie and edit 2012, TESCCC 04/19/13 page 1 of 1