Is It Plant or Animal? Comparing the Structure of Plant and Animal Cells

Is It Plant or Animal? Comparing the Structure of Plant and Animal Cells OBJECTIVE Students will prepare slides of animal cells and plant cells. Students will compare and contrast the structures that distinguish animal and plants cells and identify the structures that differentiate them. Students will create a story that walks the reader through the plant and animal cell. LEVEL Middle Grades Life Science NATIONAL STANDARDS UCP.5, C.1 CONNECTIONS TO AP AP Biology: 1 Molecules and Cells B. Cells TIME FRAME One 50 minute class MATERIALS (For a class of 28 working in groups of 2) Lugol s solution (for staining cells) methylene blue (for staining cells) 28 glass microscope slides 28 cover slips 14 droppers/pipettes 14 forceps 14 light microscopes large onion toothpicks (for collecting cheek cells) 14 amber dropper bottles (for Lugol s) tape for labeling marker for labeling 14 dropper bottles (for methylene blue) T E A C H E R Copyright 2012 Laying the Foundation, Inc., Dallas, TX. All rights reserved. Visit us online at www.ltftraining.org. AP, Pre-AP, and Advanced Placement are registered trademarks of the College Entrance Examination Board. The College Board was not involved in the production of this product. 1

TEACHER NOTES This lesson is designed to compare and contrast animal and plant cells. Microscope Mystery and The Cell is a Factory should be done prior to this lab as students will need to have knowledge of how to properly operate a microscope, as well as an understanding of organelles found in cells and the functions of these organelles. Check with your administration before preparing cheek cell smears some districts have rules that prohibit the use of student bodily material in labs. In the event that your district does prohibit this practice, cheek cell smears can be purchased from science supply houses. Students will be creating their own slides. Although the procedures provided are simple and should yield results each time, it is necessary to monitor and guide the preparation. To prepare Lugol s solution for staining: Prepare dropper bottles one per group. Make sure dropper bottles are amber in color as Lugol s will decompose as it is exposed to light. Another name for Lugol s may be Iodine Potassium Iodide, or IKI. You may also use a red/purple onion, which will not need to be dyed. However, by allowing students to dye their own onion cells, they are learning good lab technique. You will need to demonstrate, for the student, how to get the onion skin they will need only a very thin layer, which can be peeled away. If there are problems peeling the onion skin layer, you may want to prepare the pieces ahead of time a scalpel or razor blade can be used to cut very thin slices. Methylene Blue Solution: T E A C H E R Prepare dropper bottles (amber bottles are not necessary but can be used) one per group. Methylene blue may come from supply houses already hydrated (in liquid form) or in powder form. In the instance that it comes in powder form, you will need to prepare a 1% aqueous solution as follows: Dissolve 1 g of methylene blue in 75 ml of DI (distilled) water, then dilute to 100 ml. Copyright 2012 Laying the Foundation, Inc., Dallas, TX. All rights reserved. Visit us online at www.ltftraining.org. 2

REFERENCES http://www.mysciencebox.org/files/cells_lab_handout.doc http://www.flinnsci.com/sections/safety/chemicalsafety/l1051-1065_hs_solution_prep.pdf http://kingfish.coastal.edu/gk-12/_media/08/plans/high_school/cell-structure-and-functionlesson-plan.doc?id=08%3ahome&cache=cache Cheek cell images: http://science.tjc.edu/course/biology/1413/index.htm Cork cell image: http://biology.clc.uc.edu/fankhauser/labs/cell_biology/cells_lab/cork_100x_pa021953c.jpg T E A C H E R Copyright 2012 Laying the Foundation, Inc., Dallas, TX. All rights reserved. Visit us online at www.ltftraining.org. 3

DATA AND OBSERVATIONS PLANT CELL Student drawing here Student drawing here X X Structures Observed: 1. cell wall 2. cell membrane 3. nucleus (may also see chloroplast) ANIMAL CELL Student drawing here Student drawing here T E A C H E R X X Structures Observed: 1. nucleus 2. cell membrane 3. (may be left blank most other structures will be too small to see)

CONCLUSION QUESTIONS 1. Structure fits function is a common phrase used in biology. Describe how the structure of the plant cell fits its function. Include a discussion of the cell wall and large central vacuole. The plant cell has a square or rectangular structure due to the presence of the cell wall. The cell wall serves to give the plant structure. The central vacuole of the plant stores water and helps to remove toxic substances. As the central vacuole fills with water, it presses against the cell wall due to turgor pressure. When the central vacuole is empty, the cell wall collapses a bit and the plant will wilt. 2. Describe how the structure of the animal cell fits its function. Use a muscle cell as your basis for discussion. The animal cell has no specific shape instead, the shape depends upon the function of the cell. For instance, the muscle cell is elongated and striated. This is to allow the cell to contract and expand. As each muscle cell works together, contracting and expanding, muscles move. 3. Why is it necessary to stain a cell before viewing? What parts of the cell, based on your knowledge of organelles and your observations, was the stain being attracted to? Explain. Without the stain, the cell may be too difficult to see. The stain adhered to the cell membrane and nucleus in the animal cell. The stain adhered to the cell wall, cell membrane and nucleus in the plant cell. It is evident that the stain adhered to these structures because those were the only structures that became visible after staining. 4. Robert Hooke investigated the first cell using a microscope. The first cell he studied was a cork cell. Cork is dead material. When he looked into the microscope, he saw what looked like a hollow, empty space surrounded by a barrier that was rectangular in structure. What type of cell was Hooke viewing? How do you know? What organelle(s) is/are responsible for the shape? Why may this cell have been hollow, or without organelles? T E A C H E R He was viewing a plant cell. It is a plant cell because of the shape. Cell wall and cell membrane. The plant cell, without organelles, must be non-living. 5. You are a research scientist in charge of a group of research assistants. Your assistants have been given a sample of cells, none of which are labeled. As the scientist in charge, develop some identifying characteristics that allow the assistants to correctly identify the cells as either plant or animal. Plant: Rigid wall, square/rectangular in shape, nucleus, usually arranged together (student may also include organelles, etc.as long as they are correct for the plant cell, they are acceptable) Animal: no specific shape, nucleus, not necessarily arranged together (student may also include organelles, etc.as long as they are correct for the animal cell, they are acceptable)

Is It Plant or Animal? Comparing the Structure of Plant and Animal Cells Cells come in many shapes and sizes. Cells can be classified as either prokaryotic or eukaryotic. Prokaryotes, or bacteria, are single-celled organisms that live in many different environments. The common characteristic of prokaryotes is that they have no nucleus and no membrane-bound organelles. Eukaryotes, on the other hand, are all other cells fungi, protist, plants and animals. These cells contain a nucleus and membrane-bound organelles, and are much more complex in structure and function. Eukaryotes may be single-celled or multi-celled, depending upon the organism. mitochondrion ribosome rough endoplasmic reticulum microtubules (part of cytoskeleton) cytoplasm plasma membrane lysosome smooth endoplasmic reticulum free ribosome centriole nucleus nucleolus chromatin nuclear pore nuclear envelope Golgi copmlex Typical Animal Cell microtubules (part of cytoskeleton) plastid mitochondrion nucleus chloroplast golgi complex smooth endoplasmic reticulum rough endoplasmic reticulum ribosomes nucleolus nuclear pore chromatin nuclear envelope vesicle central vacuole cell wall plasma membrane free ribosome Typical Plant Cell Copyright 2012 Laying the Foundation, Inc., Dallas, TX. All rights reserved. Visit us online at www.ltftraining.org. 4

Animal cells, a type of eukaryote, are various shapes and sizes and are usually shaped based on the function they will perform. Some are elongated with many nuclei, such as a muscle cell, which must contract and relax to create movement. Brain cells have a very specific structure that allows them to receive and send messages in the nervous system. Others are rounded and spacious, such as white blood cells. What all have in common, however, are certain organelles that will provide the necessary function for that cell. All animal cells have a cell membrane and a nucleus, which is also surrounded by membrane. In fact, most organelles within an animal cell have membranes surrounding them. Skeletal Muscle Cells Brain Cell (neuron) White Blood Cells Plant cells, also a type of eukaryote, are generally square or rectangular in structure. This is due primarily the presence of a cell wall. The cell wall is composed of cellulose and is very rigid in structure and serves to give the plant tissue support. In addition to the cell wall, the plant cell has a cell membrane, located interior to the cell wall. Some organelles found within the plant cell are identical to those found within the animal cell, while others are unique to the plant such as the large central vacuole and the chloroplast. The large central vacuole serves to give the plant shape, but also to store water and toxic substances that must be removed from the plant cell. Through the process of osmosis, water will move into the plant cell and the central vacuole. Water can also be pumped into or out of the cell, as needed. When the vacuole fills with water it will press against the cell membrane and cell wall. This presence of water in the central vacuole creates a pressure build up, called turgor pressure. As water leaves the central vacuole, the pressure decreases and the cell will lose some of its shape. Hence, when a plant is wilted, watering the plant will re-create turgor pressure in the plant cells and the wilt is replaced by upright, rigid plant tissues. Copyright 2012 Laying the Foundation, Inc., Dallas, TX. All rights reserved. Visit us online at www.ltftraining.org. 5

The chloroplast serves as the organelle that functions in photosynthesis in the plant. Photosynthesis allows plants to use the energy of sunlight to create sugar for food. The green color of most plants is due to chlorophyll, a pigment found in the chloroplast, responsible for the harvesting of light energy for photosynthesis. It should be noted that the plant cell also has a mitochondria, as it also undergoes cellular respiration to create energy from food. Elodea Plant Cells Cells of a Plant Leaf Cork Cells Copyright 2012 Laying the Foundation, Inc., Dallas, TX. All rights reserved. Visit us online at www.ltftraining.org. 6

PURPOSE In this lab, you will prepare microscope slide mounts of onion cells and cheek cells. You will then make observations to identify the similarities and differences between the two types of cells. You will then create a story to guide the reader through the plant cell and the animal cell. MATERIALS dropper bottle with Lugol s solution (for staining cells) dropper bottle with methylene Blue (for staining cells) 2 glass microscope slides 2 cover slips compound microscope forceps toothpick (for collecting cheek cells) piece of onion tape for labeling marker for labeling goggles aprons Safety Alert When using glass slides and cover slips, take caution. The edges can be sharp! Wear your goggles when preparing the slides. Take caution with the staining solutions they will stain! Use care when handling your microscope. Take caution when scraping cheek cells with toothpick scrape lightly as not to tear skin inside cheek. PROCEDURE 1. To prepare the onion cell mount, obtain a small piece of onion. You will then need a very thin piece of the onion tissue. Use your forceps to separate a thin layer of skin from the onion. 2. Using Figure 1 as a guide, add two drops of Lugol s solution to the center of a glass microscope slide. 3. Place the onion skin on the Lugol s drops. 4. Place two more drops of Lugol s on the onion skin. 5. Using Figure 2 as a guide, stand a cover slip upright next to the drops slowly allow the cover slip to cover the drops ensure that there are as few bubbles as possible under the cover slip. Copyright 2012 Laying the Foundation, Inc., Dallas, TX. All rights reserved. Visit us online at www.ltftraining.org. 7

Figure 1 Figure 2 6. Tap the glass to remove any remaining bubbles the goal is very few bubbles, if any at all. 7. Begin viewing by looking at the cells under the lowest power. Record what you see in the space provided on your student answer page. 8. Move to the highest power to make your final observations. Record what you see in the space provided on your student answer page. 9. To prepare the cheek cell mount you will need to collect cells from the inside of your mouth, along the sides of the cheek. You may choose to both create your own slide, or one of you can make the slide and share it for viewing. Begin by obtaining a glass microscope slide and cover slip. 10. Add one drop of the methylene blue to the center of the glass slide. 11. Carefully collect cells from the inside cheek of your mouth. Take caution not to use too much pressure and remove too much you need a light scraping. 12. Touch the toothpick to the drop of methylene blue. This will allow the cells to drift off of the toothpick into the drop. 13. Using the same cover slip technique as you did for the plant cell, cover the drop with a cover slip and remove excess bubbles as necessary. 14. Begin viewing by looking at the cells under the lowest power. Record what you see in the space provided on your student answer page. 15. Move to the highest power to make your final observations. Record what you see in the space provided on your student answer page. Copyright 2012 Laying the Foundation, Inc., Dallas, TX. All rights reserved. Visit us online at www.ltftraining.org. 8

Is It Plant or Animal? Comparing the Structure of Plant and Animal Cells DATA AND OBSERVATIONS PLANT CELL X X Structures Observed: 1. 2. 3. ANIMAL CELL X X Structures Observed: 1. 2. 3. Copyright 2012 Laying the Foundation, Inc., Dallas, TX. All rights reserved. Visit us online at www.ltftraining.org. 9

ANALYSIS After completing your observations, you will create a story about a journey into and through a cell. You may choose either an animal or plant cell for your story. Use the outline below, as well as your book and notes, to organize your thoughts and create your story. Your story will need to be one, double-spaced, typed page, with all margins set at one inch. Story Outline I. Introduction Describe the setting how did you get into the cell? What type of cell is it? How do you know? II. Plot What is happening in the cell? What is around you? How are you traveling around in the cell? How are the different cell parts interacting with you? III. Conclusion Will you escape? What will you use to do so? Will you stay? What are the benefits of staying? What will happen to you? Copyright 2012 Laying the Foundation, Inc., Dallas, TX. All rights reserved. Visit us online at www.ltftraining.org. 10

CONCLUSION QUESTIONS 1. Structure fits function is a common phrase used in biology. Describe how the structure of the plant cell fits its function. Include a discussion of the cell wall and large central vacuole. 2. Describe how the structure of the animal cell fits its function. Use a muscle cell as your basis for discussion. 3. Why is it necessary to stain a cell before viewing? What parts of the cell, based on your knowledge of organelles and your observations, was the stain being attracted to? Explain. 4. Robert Hooke investigated the first cell using a microscope. The first cell he studied was a cork cell. Cork is dead material. When he looked into the microscope, he saw what looked like a hollow, empty space surrounded by a barrier that was rectangular in structure. What type of cell was Hooke viewing? How do you know? What organelle(s) is/are responsible for the shape? Why may this cell have been hollow, or without organelles? 5. You are a research scientist in charge of a group of research assistants. Your assistants have been given a sample of cells, none of which are labeled. As the scientist in charge, develop some identifying characteristics that allow the assistants to correctly identify the cells as either plant or animal. Copyright 2012 Laying the Foundation, Inc., Dallas, TX. All rights reserved. Visit us online at www.ltftraining.org. 11