The Cell Walk (Part 1/3)
Lesson 3 of 5
Objective: Students will construct a gym-size model of a skin cell. They will explain how the endomembranous system works and how the organelles work together to keep the cell alive.
Creating models that can be compared is very useful in student comprehension. Over the next three lesson students will research an assigned organelle. Write a script and create a life-size model of the organelle. Then they will build a gym-size cell and give tours to their peers. Here is an overview of what students will learn in this lesson.
Present the following scenario to students:
Imagine you could examine the following objects with a very powerful microscope that would allow you to see evidence of cell structure. In your lab notebooks, make a list of the items that are made of cells or were once made of cells.
- pork roast
- cell membrane
After completing your list, explain your thinking. Describe the "rule" or reason you used to decide whether something is or was once made of cells.
based on Keeley, Page. 2007. Things Made of Cells. Uncovering Student Ideas in Life Science. NSTA Press: Arlington, VA.
This is an example of student work. (Note: This student does not a clear understanding of all of these items are related. While she can explain what eukaryotic cells share, she misunderstands that bacteria don't have organelles.)
Next, introduce essential vocabulary (organelle).
The purpose for this step in the lesson is to ensure that students have a proper review of the eukaryotic cell. Begin this lesson with a review of what students know about eukaryotic cells by using A Tour of the Eukaryotic Cell powerpoint. Focus first on the electron micrograph of the organelle. Then explain how artists use the information that scientists have about the organelle's anatomy and physiology to make their drawings. Students should fill out the graphic organizer while the lecture is being given. Here is an example of a completed graphic organizer. At the end of the lecture, focus on the role of the endomembrane system.
(Note: I have noticed that students are so used to seeing perfectly drawn artist's representations of the organelles that they do not understand the wide variation between the same type of organelles in the cell. Also, it is important for students to start looking at the complex 3-D structure of these organelles so they can better understand their function.)
Student Organelle Research
Students will explore their assigned organelle in more detail in order to develop a design and script for their Cell Walk presentation. Hand students the cell walk organelle research sheet and refer them to several websites to help them get started. Typically, our starting point is Rader's Biology4Kids.com. Students will focus on the webpage for cell function and cell structure. Specifically, student teams need to focus on their specific organelle. Students can navigate wherever they would like as long as they completely answer the worksheet and evaluated the sources so they are choosing the best sources possible.
While students are researching their organelle, the teacher should move about the room answering specific student questions and aiding them in determining the relevance of individual sources. Stress to students the importance of citing all sources using APA format.
(Note: Encourage students to search a minimum of five sources to determine the most recent research on their assigned organelle. When students get stuck in the research process, I typically refer them to the source page of Wikipedia. Many times there are vetted peer reviewed studies that can help them.)
The Next Step
As a class, students should calculate the relative size of their organelle in light of the information given in the lecture. They should use the images from the powerpoint (Endoplasmic Reticulum, Golgi Apparatus, Lysosomes, Mitochondria, Nucleus, and Peroxisomes) and the measuring feature in Vernier's LoggerPro to determine the relative size of the organelles in comparison to the cell. Each student group should measure their assigned organelle.
To use the measuring feature, first open LoggerPro. Next select Insert, then Picture, and finally Picture with Photo Analysis. Students will need to select the image of their organelle. Then using the photo analysis tools, they should determine the scale of the photo and measure the organelle's dimensions. Next, they should share their findings with the class. As a class, students should determine what materials they have readily available that would be best for the construction of their organelle. (Note: In the past six years that we have completed this project, most classes choose to use tents as their organelle's basic structure. Tents are decorated inside and out depending on the class. However, for the amount of money we have available to invest (approximately $200.00) and the amount of time we have to construct the cell (approximately 1 day), tent are easy to assemble and generally meet the range in size of the organelle specifications.)
Students will write a preliminary script for a three minute presentation. Student teams will present a three minute speech to the class the next day. If not completed in class, then the speech will be homework. (Note: The presentation rubric I use I found at the website Read, Write, Think. It best meets my needs. Since I teach so many preps, once I find a resource that works for me that simply use it and give credit where credit is due. There is no sense reinventing the wheel. After each group's presentation, student teams are given a list of additional questions for their peers and their teacher. Students are required to answer these questions and add them to the revised script. After their presentation on Day 2, student groups are required to make an appointment with the the teacher outside of class. Scripts are critiqued a second time by the teacher. During this meeting, student teams will submit their powerpoint which will be used for the final presentation. They have a week and a half to complete the teacher-team meetings, revised script, and powerpoint.)