When I start my unit on cells, most of my students have some background knowledge. They have done cell analogies and can say things like "mitochondria is the powerhouse" or "a nucleus is like a brain" but I think by the time they reach high school it's time to make those definitions more applicable to how they really make an organism function. If I'm being really honest, the analogies really don't point to the function. The nucleus doesn't make decisions for the cell...it's stores DNA. So the analogy that it is like a brain, leads to incorrect assumptions about how cells really work. Before we dig into the endomembrane system, which is where I think they really start to see connections, I like to spend 3-4 days reviewing what organelles are found in which cells and the basic functions of each organelle. You can spend more or less time, depending on your students prior knowledge and needs.
Pro vs Animal vs Plant Drawings
Usually after a unit, the 1st day of the new it we do a short intro of what they are going to learn, but then we do an activity that is a little lighter on the brain power/critical thinking scale. I think it's important to build some days in that aren't super heavy, and they can have some quieter time to do work that is important, but that isn't draining. We start with reviewing what cells organelles look like, names of organelles, and different types of cells. We do this with coloring! This may not be everyone's cup of tea, and that's ok, but in the end they need to be able to recognize similarities and differences between cells, where those organelles are located, and how they look. This task accomplishes that.
The Directions: I don't just say, ok, here's some pictures, now color.
I print the prokaryote cell on it's own page and the plant cell and animal cell are printed together on same page. (Just use a copier --- 1 page to 2 pages and it will 1/2 it up) Here are the ones that I love the most but you can use your favorite drawings. They tape the drawings into their notebook, side by side, so they can see all three at the same time.
They begin color-coding each organelle. For example, cell membrane is blue. All three have a cell membrane so they color all three in blue. The cell wall they might make pink and so they color the cell wall in the prokaryote and plant cell pink. They continue to do this until they have colored all three pictures.
Then that same day or the next day, depending on time, we create a 3 circle Venn diagram on the next page in our notebook and begin filling it out using the pictures. This can be done as whole class notes, with a partner, one their own...just make sure you provide a key/feedback so students can make sure they are correct. I also use this time to talk about differences between prokaryotic and eukaryotic cells, having them focus on those overlaps in the Venn diagram. I find completing notes this way vs traditional lecture to be a bit more engaging.
Organelle Functions
When students are done learning the difference in organelles found in each cell and between prokaryotes and eukaryotes, we move on to functions.
Now, I used to be the teacher who went through every organelle on a PowerPoint slide and had kids write the definitions. It.took.forever. and I don't think they ever remembered them.
I give them a table with the name of the organelle and the function, and they put it in their notebook as notes. Then I try to review those functions using the Cells with Missing Organelle Cards. Each card has a missing organelle or set of organelles. There are 3 different worksheet that can be used with them. One is just recall the missing the organelle, one has more specific questions about functions, and the other one is more open-ended discussion type of questions. These cards make great station activities or review as well. You can find them to purchase here: https://amzn.to/3KS5dWD. Below is an example of the cards that are included. A key for worksheets is also inlcuded.
Once students finish that, I like to give them a creative assignment where they use the definitions. They create comics where the organelles have conversations. I like to give them certain criteria to meet, so they really have to think about what organelles they want to use. The only real rules are: the functions have to be embedded somehow, and they can't just outright say what their function is. Here are some examples of the criteria we have given: 2 organelles that are fighting, 2 organelles that are happy to have each other, 3 organelles where 1 organelle is crying, 2 organelles that are in love, etc. The possibilities are endless.
After students spend some time on organelle functions, we like to do a cell lab with microscopes. Kids get to look at different cell types under the microscope and compare structures.
It doesn't have to be complicated! Put out a generic animal cell slide (usually cheek smear is a good one), a generic plant (onion cross section), and bacteria. Have them find each one on high power and draw it. I make sure mine color them and then label all of the parts they can see. Usually it is just cell membrane, cell wall, nucleus, sometimes a vacuole, and cytoplasm for the plant and animal, then the bacteria they can only see the structure/shape.
After they have done that, they get a mystery slide. They write a CER, explaining whether they think the mystery cell is a plant, animal, or bacteria. This requires them to use the observations they just made to collect evidence on their mystery slide.
Next up, endomembrane system! I will save this for another blog post, but this is usually our next step after the lab. We have them complete an activity about the endomembrane system, so they can really see how the organelles work together to build, transport, and export proteins in a cell.
Check back later for more posts about cells!
Happy Teaching! Mrs. Townsend