The Cell City
Teaching students to memorize all of the organelles in prokaryotic cells and eukaryotic plant and animal cells can be a tedious job. Instead, have students complete a project where they are asked to create an analogy between a cell and a city. The cell can be thought of as its own miniature city: each organelle represents a part of a city that carries out a specific job or function so that the cell can survive. For example, the nucleus would be like the town hall of a small city. The nucleus is in charge of controlling all of the actions of the cell, just as the town hall is responsible for controlling the activities. Additionally, the mitochondria can be compared to the power company in a town. The mitochondria are responsible for powering the cell through cellular respiration and the formation of ATP. Similarly, the power company produces energy for the city. Students should be asked to come up with a comparison for all major cellular organelles to develop a complete cell city analogy. The final project would consist of a poster presentation or 3D model of the city that is labeled with both the cell and city parts. A written summary explaining the analogy should also be included. Also, this activity can be extended by using the "cell city" as an example and then asking students to come up with their own analogy such as a classroom, school bus, car, kitchen, house, etc.
Infectious Disease Case Studies
In this activity students are given the opportunity to be the doctor and diagnose patients that are presenting with various infectious diseases. Provide the students with a list of patients and a brief summary of their symptoms. The goal of the activity is to have students correctly diagnose the patients using the Internet and their understanding of pathogens. Students should use websites such as Web MD and Mayo Clinic to assess the symptoms of their patients. In addition to correctly diagnose their patients, students should determine what type of pathogen caused the infectious disease (virus, bacteria, protist or fungus) and should develop a plan for treatment. Some diseases that can be used are: athlete's foot (fungus), HIV/AIDS (virus), strep throat (bacteria), tetanus (bacteria), amebic dysentery (bacteria), and malaria (protist).
Spread of Disease Laboratory
A great way to demonstrate the transmission of disease is to have students complete the spread of disease laboratory experiment. In this lab, students are each given a cup with a clear, colorless solution and a disposable pipette. All students in the class, except for one, are given a cup with just water in it. One student in class is the "index patient" and their cup has a few drops of sodium hydroxide in it. None of the students know who the index patient is at the start of the lab. Students are instructed to "come in contact" with 3 other people in the class by exchanging a pipette full of solution with each person. This should be completed in rounds and signaled by the instructor. Students should keep track of with whom they have come in contact with in their data table. At the end of the third round a drop of phenolphthalein should be added to each students' cup. Students who were infected by the disease will end up with a pink solution in their cup. As a class, students should create a tree to determine how the disease was transmitted and to determine who the index patient was. This activity promotes collaboration between all students in the classroom and demonstrates how quickly a disease can be spread throughout a population. Additionally, this activity can be repeated with more than one index patient to make the determination of transmission more difficult for the class to solve.
In this unit is important to understand that there are several pathogens that cause disease in humans: bacteria, fungi, protists, and viruses. An interactive way to get students involved in their learning and promote reading is to have students participate in a pathogen jigsaw. Students should be divided into groups of four for this activity. Each member in a group will be assigned a different pathogen that they are responsible for learning about. Students are given short articles with information about the pathogens and they are given time to read the information and look for key points and facts. Students are instructed to become an "expert" on their specific pathogen. Then, each expert will teach the other three members in their group about the pathogen they read about. Students can be given a graphic organizer to take notes about each pathogen so that at the end of the activity they have information about viruses, bacteria, fungi and protists.
The use of light microscopes is essential for this unit. Students should be given several opportunities throughout the unit to observe life at the cellular level using a microscope. There are many different ways to incorporate microscopes into this unit, such as: the use of prepared slides to observe microscopic bacteria, fungi and protists, the use of the plant Elodea to observe chloroplasts, and the use of potato or cork to observe plant cell walls.
HeLa Cells and Chromosome Spreads
CellServ produces a kit that will allow students to use HeLa cells in the lab to observe cells and chromosomes under the microscope. Students are given microtubules containing HeLa cells that have been fixed in solution prior to metaphase in mitosis. Students use pipettes to drop the cell solution onto clean microscope slides and then stain the slides with stain that is included in the kit. Once the slides have dried, students are able to look for cells under the microscope. Using the oil immersion lens on a light microscope students should be able to see chromosomes inside of the cells.
There are several applications that are available on the iPad that give students a look at cellular life and the spread of disease. A list of a few of these applications and a short summary are below.
Powers of Minus Ten – Cells and Genetics: This application allows students to virtually zoom in through a human hand to observe skin and blood cells. The application can be used to show students different phases of mitosis, differentiate between different types of cells, and identify cell parts.
Plague Inc.: This application is a simulation about how a virus can spread throughout the globe rapidly. A virus rapidly reproduces and mutates as students try to stop it by creating vaccines and ways to prevent the spread or cure the disease.
3D Cell Simulation and Stain Tool: This application allows students to virtually look at 3D plant and animal cells. The application has information about cellular organelles and students can stain the cell to focus on one or more organelles at a time.