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This lab is not only a staple in Biology, but it is a student favorite. In my very first blog (YAY!), I would like to share with you my version of the last meal macromolecule lab, which is set-up as a forensics who-dun-it murder mystery. Although the concept of the lab isn't new, I wrote this entire activity from scratch years ago. As teachers, we continually tweak things to make them better, and I've finally reached a point where I'm 100% happy with this lab. By blogging, I hope to expound on my labs and activities to help you gain some confidence and insight before bringing it into your own classroom. You can follow the link to the lab and download the preview, which includes the backstory (Eugene's murder), the directions, and the student hand out.
I would be lying though if I said online labs and activities were a lesser version of actual hands-on labs. I think in a lot of ways they are better. As you can see from the YouTube trailer, students are able to self-pace their way through the lab, which is split up into 5 parts that mimic a 5-E lesson. This, combined with the fact that it is self-grading and interactive, means students really do learn effectively. Plus, there's no prep, clean-up, or grading, which is amazing! Onto my hands-on version of the lab! There are other murder mystery macromolecule labs online, and they have you buying potatoes and eggs and all sorts of groceries and then blending them up to create your solutions. I HIGHLY suggest simply ordering dried versions of the macromolecules that you can just add water to - plus, because they are dried, you can keep them year after year in your storage cabinets. I have a picture of the ones that I ordered from Amazon. At this point, the fructose and gelatin are three years old! Below I have pictures of the positive controls (left) and the stomach contents (right), which is a combination of fructose, gelatin, and red dye.
I know this is going to seem like a waste to some people, but for messy labs like this, I opt to use small plastic cups instead of beakers. My classroom is oooooold and I do not have large lab desks that I can set-up as stations. Plus, I teach very squirrely freshman. For safety purposes, I have my students work in pairs with their butts in their chairs for almost the entire lab. The only time they will need to get up is to put their tests tubes in the hot water bath for the simple carbs test and to rinse their test tubes out between macromolecule tests (I do have 5 sinks around the room). Having my lab set-up this way requires a little bit more prep, but remember, you could have one station set up for each test and have students rotate around the room. I have pictures below of how I do it. Each pair of students will have 6 small cups containing water, fructose solution, starch solution, oil, gelatin solution, and stomach contents. I line the cups up like the picture below, fill up a large pitcher of one of the solutions and just pour all the cups in that row. It goes pretty fast. As you can see, I put a little green string and a pom pom ball in the stomach contents and call it seaweed and fish eggs for fun ;)
 You can see each partner set-up below. Each of the 6 cups gets its own plastic pipette. Each pair will also get three glass test tubes labeled "+" for the positive test, "-" for the negative test (always water), and "S" for the stomach contents in a test tube rack. Each desk gets the four indicators (Benedicts, Biuret, Lugol/Iodine, Sudan III) in dropper bottles and some Lysol wipes. I also took a picture of what I write on the board when I go over the lab with students.
The tests are pretty straight forward. I took these pictures last year and have switched up the storyline slightly. This year, the stomach only has simple carbs and protein in it but the picture below shows a positive result for complex carbs (which it won't if you use my new updated version). I would say the only tips and tricks I have is:
What about the flow of the entire lesson? I teach 90-minute classes, so for me it is easy to do a PowerPoint and this lab all in one class period. If you teach 45-minute classes, you could teach the PowerPoint and do the front page of the student lab handout one class period, and then have students do the Last Meal Macromolecule Lab the following class period.
I teach my students an introductory lesson on macromolecules while they take guided notes. My personal preference is to go over the pre-lab questions as a class (hand-raising). Then I call on students to each read a paragraph of the backstory. I find that student engagement is enhanced if we all read it together. From there we actually go over the Backstory part of the worksheet. I want to make sure students know what macromolecules were in each of Eugene's meal before they start. I am big into gradual release. Finally, I go over the gist of the lab with them and let them perform the tests on their own. Remind them not to shout of who the murderer is since they will all be finishing at different times. I hope you found some of my tips helpful! Please leave a comment below or feel free to email me at [email protected]. I do have an email list if you would like to get notifications of new products, blog posts, or TPT sales. And as always...have fun! Ashley Grapes (Science with Grapes)
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