Identifying Organic Compounds in the Lab (Day 1 of 5)
Lesson 1 of 15
Objective: Students will be able to identify proteins, carbohydrates, saccharides, and lipids in the lab.
Every biology class utilizes an organic compound identification lab; for me, this is one of the best. By slowing down to introduce the lab equipment and safety as a separate lesson rather than a quick reminder at the start of the lab procure day, we engage student curiosity and allow them to fully digest the many complex test procedures they will be following.
Adding in a student choice day engages students and makes things more personal for them which creates a very positive, collaborative, and inquiry based lesson day where we work together to figure out how to work with our diverse samples and asses the accuracy of our results. And finally, giving students an opportunity to share out their original data as a class allows them to critically compare and analyze data against their prior knowledge and come up with interesting questions they'd like to investigate in the future.
The lab is broken up into a five day series:
During Day 1, students complete a pre-lab activity and explore the equipment, procedures, and safety guidelines for the series. Standards: W.9-10.1, SL.9-10.1, SP1, SP3, SP4, SP8, XC-SF-HS-2
On Day 2, students focus on the lipid and saccharide tests for five samples. Standards: SL.9-10.1, SP1, SP3, SP4, SP8, XC-SF-HS-2
During Day 3, students focus on the protein and starch tests for five samples and brainstorm their own group samples to bring in for testing. Standards: SL.9-10.1, SP1, SP3, SP4, SP8, XC-SF-HS-2
During Day 4, student groups work to test their own five samples. Standards: SL.9-10.1, SP1, SP3, SP4, SP8, XC-SF-HS-2
And on Day 5, we come back together as a large group to assess our lab work results and review the major concepts of the series. Standards: W.9-10.1, SL.9-10.1, SP1, SP3, SP4, SP8, XC-SF-HS-2
1. Ask students to go to their lab tables and examine the equipment you have set up at each station. Allow students the time to really look at and manipulate the equipment--they will be curious and interested! Tell students to look at each piece and discuss the following prompts:
What do you think each piece of equipment does?
What are they called?
What are you curious about?
2. After 5-10 minutes, use the spokesperson protocol to share out group impressions and knowledge about the lab equipment they saw and discussed. Hold up each piece of equipment and ask for students to share with you what they know about it. You can also hold one up and ask them to guess what it is called--they love this!
- Note: Students are going to have lots of questions about the names of each piece of equipment and how to use them. Specifically, the test tube holder comes up as a curiosity for them. Overall, the equipment is fairly intuitive to use, the engagement of this lesson comes from their chance to really handle and manipulate the pieces without having to rush distractedly right into a lab procedure.
3. Announce that they will be using all of this equipment over the next few days as they work to identify organic compounds. Take the final few minutes of this portion of the lesson to point out any specific safety hazards.
I review the following pieces of information:
- Test tube holder and tongs: the right way/wrong way to hold them and that proximity between locations means less chance of breaking glass
- Hot plate: monitoring materials on the hot plate is essential, use of PPE, where to place it on the lab table to prevent accidents, how much water to put in a water bath
- General reminders: no eating or drinking in the lab, no eating or drinking of the lab materials
I have included four short powerpoint slides about today's activity to assist you and your students in your preparation for tomorrow's activities.
1. Pass out the lab document for this activity.
2. Ask students to turn to the second page and spend about five minutes having volunteers read the introduction and purpose of the lab.
3. Point out where the lab procedures are and the the data table with the types of substances they will test over the next two days.
4. Ask students to turn back to the first page and in their lab groups, spend 10 minutes discussing and making their predictions for each substance (does it contain lipids? saccharides? carbohydrate? proteins? all? none?) and to fill out the indicator information.
- Note: Spending time in groups on this pre-lab work helps to ensure that the lab days using equipment and analyzing data will be efficient and informative for students. This time allows them to figure out which task will be their individual responsibility, clarifies that every person understands each test, and gives each group the opportunity to discuss their hypotheses for each sample and check for understanding and logic in relation to the broader topic of organic compounds.
5. For the last 10 minutes, ask students to pick two tasks from a list of 8 that they will be responsible for writing about in their collaborative lab report. You can see my task breakdown on my powerpoint slides.
6. This pre-lab section will be turned in as part of their complete lab report for this multi-day activity and as you can see from the student work sample, the pre-lab work gets all of the students in synch as to the goals for the activity, the procedures for each lab test, and the roles each of them will play during the lab series.
- Note: Each student group was required to turn in one typed, group lab report and data document which included the pre-lab work as seen in the student work sample above. Students worked on their pre-lab during this class period on their draft documents by hand and then went home to type it all up as a cohesive report for the final turn in day. I checked in with each student group during this session and at the start of the next lab session to ensure that they all understood their lab procedure and background information and to answer any clarifying questions. All of the information needed to fill out this page could be found in their lab document and students were encouraged to discuss their predictions for the lab. I told them their predictions would not be graded as correct or incorrect and that I was more interested in a discussion about what organic compounds could reasonably be expected to be found in our familiar food samples.
- The major clarifying questions were the following: 1) Students were unfamiliar with the term reagent and wanted to discuss it further. 2) Students weren't sure how to tell the color change/difference the protein analysis reagent biuret from the description in their lab document which states it turns from blue to blue-violet. We discussed how some of this would be better understood during the lab as they compared the colors in real time. I reassured them that I would be there to assist and support their analysis and conclusions.
Now on to Day 2!