Identifying Organic Compounds in the Lab (Day 5 of 5)

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Students will be able to identify proteins, carbohydrates, saccharides, and lipids in the lab.

Big Idea

Get your students acquainted with organic compounds in their everyday lives using this engaging lab activity!

Notes for the Teacher

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

The Classroom Flow: Preparing to Present

15 minutes

1.  Ask students to take out their lab document.

2.  Announce that students will have 15 minutes to complete any remaining lab tests on their chosen substances and to consider the following prompts for their class share out as a group:

What substances did you choose?  Why?  What did you find out about them?

What surprised you about your data?

What challenges did you encounter?  How did you overcome them?

The Classroom Flow: Presenting Data

25 minutes

1.  Use the spokesperson protocol for student group data presentations.  As students share their results, focus upon the connection between student predictions and the data they collected.  At every available opportunity, circle back to our scientific vocabulary:  independent variable, dependent variable, error analysis.

2.  Pass out a small white board and a marker to each lab group.  Ask each group to pick one of their samples that they want to present to the group as a mini-quiz item.  Give students 1-2 minutes to discuss and choose their sample.  Remind them to talk quietly so that the other groups can't hear them!

3.  Tell students that each group will say the name of their sample and that all groups will have one minute to discuss and write down on their group whiteboard which of the organic compounds we tested they believe are in that sample:  saccharides/starches (carbohydrates), lipids, proteins, or none.  

  • Note:  Students will get into this somewhat-competitive task in a serious way!  I really enjoyed watching their motivation and serious efforts to discuss and come to the correct conclusion about the components in each group's sample.

4.  Tell groups that they should now raise up their white boards for all of us to see.  Ask any particularly eager group to share out their rationale for their written ideas.  Then go back to the original group and ask them to read off their test results for comparison.  Be ready for lots of celebrations and groans and kids congratulate each other on their ideas and debate the validity of what they hear.

  • Note:  Lots of great conversation happened during this activity, especially when a group's data seemed really off (example:  water testing positive for lipids).  We were able to talk about human error and lab procedures that could ensure accuracy in results.  We also talked about ways to confirm results like checking in with another group or looking at food labels for more information.

5.  Repeat this process for each of the 8 lab groups.  If you have any extra time, ask groups to find one more zinger that might stump the group--you will get lots of volunteers!  

The Classroom Flow: Lab Reports

10 minutes

With the remaining time, remind students that they will be completing a collaborative lab report for their results.  You can refer them to the unit powerpoint slides #23-24 for more information.  Detailed directions for the collaborative lab report are also found on the last page of the organic compound lab document.  I also shared our group lab report rubric with students as well to further ensure that their final products would be great.  

Check out my video clip outlining some points to consider in terms of lab report construction and grading:

1.  Overall quality:  my thinking about why the student work was so good overall

2.  Issues that came up that caused students to lose points on their lab reports

3.  Use of job checklists to monitor the group aspect of grading lap reports and how to handle groups that did not work well together to create the final product

4. How to prevent scenarios where one student is doing more than their fair share of the written work

 Lab reports were done by students on their own time outside of class.  As you will see from both student work sample 1 and student work sample 2, the overall product quality level was high. My biggest challenge in assigning this report as a collaborative activity was that it required adequate time for preparation outside of class for students with full extra curricular schedules and no drivers licenses.  For that reason, I gave one full week and a weekend for students to complete the work as a team.