Dr. Gillian Backus, Department of Biology, Northern Virginia Community College
In this activity, students create or critique a narrative in which a biological cell is compared to a city. Through writing and discussion, students learn to better visualize cell organelles, making connections between their structure and function by using the metaphor of a city. Students gain an appreciation for the dynamic nature of cells and come to picture how cells constantly build, recycle, send, and receive messages, package materials, and communicate.
With a dynamic understanding of cells, rather than a static one, students are then prepared for future units involving cellular function. The groundwork provided by this activity allows students to apply their knowledge to discussions of various cellular diseases including mitochondrial disease, cancer, and lysosomal disorders. Students become more prepared to think critically about the importance of maintaining internal homeostasis and how cellular dysfunction is linked to human health on a macro level.
Because this project requires students to compare a cell to a complex organization such as a city, students must research how cities work and understand the many critical functions that cities fulfill. The most successful projects are those that demonstrate a comprehensive understanding of the infrastructure of a city and accurately compare these city components, where appropriate, with that of a cell.
By requiring students to explain these concepts creatively, this activity helps students to own their knowledge. By asking students to justify their decisions and comparisons, it prompts them to put their critical thinking abilities into action.
Courses Into Which This Activity Could Fit
This activity is well suited for biology courses that introduce students to cellular structure and function, such as:
- Biology 101 (college-level introductory biology, for majors or non-majors)
- Introductory cell biology
- Introductory anatomy and physiology
This activity may also be useful in courses such as forensics and psychology in which a basic knowledge of biology is warranted but cannot be assumed. And the activity is valuable for inter-disciplinary courses focused on health topics such as cancer, diabetes, environmental toxins, global health, and food systems.
This activity is an open-ended thought experiment in which students use critical and creative thinking to own their knowledge of the ways in which a cell is like a city.
Students often have trouble understanding abstract biological concepts or physical structures not visible to the naked eye. Most of the organelles in a cell are not visible even with a very good light microscope; therefore, the only pictures we have of organelles are grainy images produced by transmission electron microscopes. This project enriches students’ learning about invisible structures in the natural world. This is a powerful skill, applicable across many issues, including how to visualize and understand health issues such as cancer, inflammation, and diabetes.
This activity helps students to improve their abilities in reasoning through analogies, making learning less daunting because the learning links something unknown to something familiar. Since many of the dangers we face as a society are also invisible, teaching students how, in a sense, to make the invisible visible is to give them a great tool that they can use when confronted with invisible threats or challenges in the future. It helps them relate to problems we cannot see.
The core part of this activity includes the following components:
- Students either create an analogy of a cell as a city or critique a YouTube video of work done by other students. They may also choose another analogy. I have had them compare a cell to a cruise ship, spaceship, and human body, with good results.Students should have prepared for class by reading about the parts of cells in their textbooks. In class, the instructor polls the class for cell organelles that they remember from the class readings or from previous biology classes. The instructor may informally quiz them on what each organelle does. Depending on how well the students remember their basic cellular biology, the instructor can review the parts of a cell via a PowerPoint presentation. Then, the students brainstorm the critical parts of a city and what their functions are. The instructor collects this information orally and assesses students’ fundamental knowledge of cities. For homework, students perform further research on the parts of the city (or cruise ship or space ship) that they would like to compare. The instructor should model what a good analogy is by including images of city departments interspersed with relevant cellular organelles.For example, images of a cell’s nucleus could be compared to the control center or bridge of a cruise ship. The nucleus, just like the bridge of the ship, is the command center and ultimate control center. The cell’s nucleus has regulatory functions much as the bridge of the ship monitors and maintains the ship’s multiple system.
A second analogy might be to draw a comparison between a cellular vesicle and a city bus. Just like a city bus, cellular vesicles generally leave one location and go to a second location, carrying cargo, and dropping it off at the destination.
- During a second class period, students gather in small groups to brainstorm what different city parts correspond to which organelles and why. The instructor collects feedback and corrects any major misconceptions. This session is designed to get the students thinking in analogies. Students write their rough drafts of their project, due the following week. At a minimum, students are required to create and complete a comprehensive chart listing the organelles, what they are being compared to, and a justification of their comparison. To ensure the students complete this assignment, this assignment is worth a 25-point quiz grade, and a “ticket to class.”
- Students may create a written narrative as a “tour guide” script, or they may use other media such as Prezis, PowerPoints, children’s books, and websites to illustrate their analogies. To create their project or to create a film critique, students do independent research on the parts of a cell and their functions, and they often must do research on the parts of a city or cruise ship, or whatever it is to which they are drawing an analogy.
- If they are critiquing a comparison made by someone else, students refer to YouTube videos of how a cell is like a city posted by other people (doing a search for “how is a cell like a city” from within www.youtube.com). In a narrative format, students critique each video, asking themselves what inaccuracies are present and how they would remedy them. Students connect certain points in their narrative to specific time stamps in the YouTube video. Narratives have been received in the form of papers, children’s stories, PowerPoint shows, Prezis, and posters.
- The structure of the narrative and its component parts are open-ended, but it must be written so that a person unfamiliar with biology would understand.
The project can be expanded in ways that make the activities more interactive:
- Students can identify the parts of a city and the respective functions as a whole-class brainstorming session.
- Students can research the parts of a cell, relate those components to the components of a city, and justify their comparisons in small groups during class or via a discussion board online.
- Students can debate the merits of one part of the cell vs. another. The instructor may announce budget cuts, upon which students are assigned to argue for a specific organelle and must justify its existence over that of other parts of the cell.
- Exemplary projects can be selected by the instructor as models and then redistributed to the class to wrestle with a “what if?” scenario. What if this particular city had cancer—what would the city look like and how would its functions change? If this city was diabetic, what would it look like and how would it function differently? For example, a city with cancer might have a “rogue” city hall and might force its citizens to make prodigious amount of faulty products at the factories (ribosomes). A city that represented a diabetic cell would essentially starve. The city would be cut off from its food supply, which would force the city to use its existing resources to power its power plants. Once the city depleted its existing resources, it would begin to decay and would die. Any number of cellular disorders can be applied to the analogy to challenge students’ critical thinking and understanding of cell organelles (and cities).
- At the instructor’s discretion, and depending on available time, students may share their projects with the class. At this point, students may also be asked to share their project with students at elementary schools, day cares, or the public library as an extension project.
- To obtain closure on this activity, students watch the three-minute video “Inner Lives of a Cell” (http://www.youtube.com/watch?v=wJyUtbn0O5Y) and try to identify the organelles and processes illustrated. This is a sophisticated video that requires excellent foundational knowledge of cellular biology to appreciate its embedded nuances. Alternatively, this video can be shown while students are in the midst of creating their project to generate ideas, although students may not be able to appreciate its sophistication.
“Cell as a City” can complement a number of other types of projects:
- Any situation in which students must justify or explain their reasoning
- A project at the end of the semester when students design their own single-celled organism, accompanied by an account of its natural selection and evolution
- Other projects in which students must write in lay terms (for example, to explain photosynthesis in terms that anyone can understand)
- Activities where students must assess the validity of an outside source. In the “cell as city” activity students must use additional resources (textbook, web searches) to research their analogy or to prepare their critique. Students often fail to adequately compare one website to another; they usually cite the first resource they locate, regardless of its author or how recently it has been updated. In this increasingly complex technological world, students need to be challenged to critically analyze the sources they find.
- Other topics for which analogies can be built that aid learning (e.g., enzymes, osmosis, cellular respiration). For example, I use the analogy of a “glove” “fitting” a substrate when I discuss the induced-fit model of enzymatic action. The electron transport chain component of cellular respiration is often likened to a series of steps that the electron “falls” down.
Scientific Concepts Addressed and Related Civic Issues
This activity addresses several scientific concepts within biology, including the structure of the organelles of a cell, the functions of these organelles, and the interconnectedness of cellular components.
In this activity students connect scientific knowledge with social questions pertaining to human health. For example, many students have a flawed understanding of many diseases, including cancer, diabetes, mitochondrial disease, and lysosomal disease. By understanding how cells work, students are primed for insights as to how cancer treatment works, the importance of regulating glucose levels, and the importance of lysosomal and mitochondrial functions. Understanding cells is also critical to understanding the division of labor among our own organs, the way in which our immune system “fights” infection, and other health-related topics. This project helps students own the knowledge that will assist them in making their own health care decisions.
Week 1: Thirty minutes of class time are needed to introduce the project. In the second class period in which students brainstorm which city parts correspond to which organelle(s) and why, approximately 20 minutes will be needed, depending on how strongly the students’ understanding is developing.
Week 2: Students’ rough drafts of their narratives are due. Students will gather in small groups to get feedback from a classmate (15 minutes), and then 15 minutes as an entire class are needed to clarify any other cell parts.
Week 3: Projects are collected, and the time required will depend on whether the students share their projects with the class or share them at elementary schools, day care centers, or a public library as an extension project. Twenty minutes are needed for students to watch and discuss the video “Inner Lives of a Cell” (http://www.youtube.com/watch?v=wJyUtbn0O5Y).
Prior knowledge required
Students should be assigned to read descriptions of the parts of the cell on their own before beginning this activity. Any college-level biology textbook will have this information. In addition, there are any number of internet resources from Wikipedia to youtube.com where students can enter a simple search term and get a healthy array of reasonable resources. The Howard Hughes Medical Institute website (www.hhmi.org/biointeractive) has a wide variety of online resources. Students usually study the parts of a cell in high school biology, and often students are familiar with the vocabulary of cell parts (e.g., nucleus, plasma membrane, mitochondrion, Golgi apparatus, endoplasmic reticulum). However, their working knowledge is generally not comprehensive. It is important to build on their existing knowledge and to use this project to correct inaccuracies. For example, when using a cruise ship analogy, students have likened ribosomes to the chefs in the kitchen because both make proteins for the staff to eat. However, in a cell, proteins are not synthesized for use as food or energy.
Students also need knowledge of the components of a city and their functions (particularly its infrastructure, for example, its water and sewer systems, the behind-the-scenes work of town hall employees, and what really happens inside a post office). We often assume that students understand how cities “work,” but I have seen that often their understandings are shallow or misinformed. For example, students may correctly make a comparison between the engine room of a cruise ship and a mitochondrion; however, they demonstrate the limits of their understanding by explaining that the engine is used to move the ship, when in fact it is used to power everything on the ship. I use the structure of the classroom building to draw the parallels between what you see, and what is necessary infrastructure. Where does the light come from? What does it look like behind the walls? Above the ceiling? Sometimes I call up a subway map or a map of a sewer system as I explain that often what is important is not clearly visible.
- Internet access (for further resources and images, and possibly as their media outlet). I allow students to submit Prezis, PowerPoint presentations, and homemade websites. Thus, the Internet is a medium both for collecting information and for displaying information.
- A textbook (or specific internet sites) covering the parts of a cell and their functions such as J.B. Reece, et. al., Campbell Biology: Concepts and Connections, 8th Boston: Pearson, 2015. Pp. 50-71. Or BiologyJunction (http://www.biologyjunction.com/cell_functions.htm)
- Access to the video “Inner Lives of a Cell” at http://www.youtube.com/watch?v=wJyUtbn0O5Y.
Context and Concepts for Instructors
- Instructor knowledge and sample materials
Instructors should have knowledge of basic cellular biology. Sample materials for this activity are provided below, including samples of student work, rubrics for grading, and directions for students.
Instructors should keep in mind that the amount of time allotted for brainstorming how a cell is like a city depends on the preparedness of the students.
In my experience, showing the YouTube video “Inner Lives of a Cell” after the cell projects have been turned in is preferable to showing the video early in the project timeline—the students have a much better sense of the dynamic nature of cells and are more actively engaged in the processes they see occurring in the video. Students have a much easier time recognizing the organelles “at work” once they have completed this project.
- Analogy or critique?
The instructor has the discretion to offer the choice of analogy or critique. Generally, the greater the options, the happier the students are. The drawback for the instructor of offering either a critique or an analogy is the need to consult more than one rubric when grading. This decision may be driven by time or class size.
- Process for working with the rough drafts
The timing for this part of the project can range from a part of one class to do some very basic brainstorming to a more extensive peer review and group discussion. The timing depends at least in part on how seriously the students wrote their rough drafts. Some students may have a nearly final copy, while others have only just begun to really think about the assignment. A peer consultation allows prepared students to share their thoughts and underprepared students to become inspired with ideas. The instructor may choose to collect the rough draft for points or not. Students are then encouraged to ask for clarification on specific organelles that confuse them, which generally leads to an engaged, student-driven class. The instructor should be prepared to potentially spend the entire class period reviewing organelle structure and function. In addition, the instructor must be flexible to go where the students need him/her to go. Between week 2 and week 3, students’ main assignment is to complete this project as homework.
What students will be able to do
This activity requires students to be creative and organized. Upon completion of the activity students will be able to:
- Identify similarities between complex cellular processes and visible processes in the world with which they are already familiar
- Explain biology-related ideas to a lay audience in a creative, accessible way
- Describe the parts of a cell, how they work, and how they work together
- Create analogies and justify them by citing specific evidence
- Cite resources appropriate to the scientific question at hand
Ways that this activity enriches the engagement of citizens with social and civic problems having underlying scientific issues
This activity connects to several SENCER ideals, including:
- SENCER locates the responsibilities (the burdens and the pleasures) of discovery as the work of the student.
This project gives students one model for how to engage deeply with material on a scientific topic. Since they have to create analogies for each organelle, they must thoroughly understand its function and how it is like (or not like) an analogous part of a city, cruise ship, or spaceship. This obligates students to own their learning, while making science less intimidating. The hope is that when they later encounter a more difficult scientific issue or problem, they will be more willing to engage with it, attempt to understand it, and learn from it.
Through this project, students learn to probe more deeply into the material. They cannot simply list and memorize the parts of the cell; instead, they must create a frame of reference, an accurate analogy. This project also teaches students to observe similarities between (1) concepts in science, and (2) concepts in daily life that are more familiar. Making analogies makes learning less daunting, because the learning links something unknown to something that is already well understood.
This is an open-ended assignment. There are limitless possible narratives and answers. Students are provided a rubric to help them structure their arguments. But fundamentally, they learn about cellular organelles by themselves and in self-directed discussion with their peers; the learning was their responsibility.
- “…SENCER hopes to help students overcome … unfounded fears … of science.”
This activity helps students to overcome y relating the structure and function of cells to something familiar to them, students discover that cells are interesting, dynamic places and that cells really aren’t so foreign and difficult when compared with something as familiar (though still complex) as a city.
The College Board’s Enduring Understandings That Connect Most Closely
Big Idea: Biological systems interact
Enduring Understanding: Interactions within biological systems lead to complex properties
Enduring Understanding: Naturally occurring diversity among and between components of biological systems affects interactions and the environment
Other central concept: The structure and function of the subcellular compartments, and their interactions, provide essential cellular processes.
Other central concept: Interactions between molecules affect their structure and function.
Big Idea: Living Systems Store, retrieve, transmit, and respond to information.
Enduring Understanding: Cells communicate by generating, transmitting, and receiving chemical signals.
Other central concept: Cells communicate with each other through direct contact or from a distance by chemical signaling.
Other central concept: Cell signaling pathways can link cellular reception with cellular response.
Big Idea: Biological systems utilize free energy1 and molecular building blocks to grow, reproduce, and maintain dynamic homeostasis.
Enduring Understanding: Growth, reproduction, and dynamic homeostasis require that cells create and maintain internal environments.
Other central concept: Eukaryotic cells maintain internal membranes that partition the cell.
Other central concept: Variation in molecular and cellular units provides cells with a wide range of functions.