Identifying Organic Compounds in the Lab (Day 3 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: Testing for Lipids and Proteins

30 minutes

1.  Ask students to take out their lab document and turn to page three with lab procedures for the two tests they will be focusing on today:  starch and proteins.

 2. Show the lab equipment to students again and indicate where they can find any necessary materials.  

3.  Take any questions students might have from yesterday.  Review chemical/reagent safety as outlined on my brief powerpoint slides.

4.  Time for students to get to work!  Check out the organic chemistry lab tips and tricks document for suggestions about ways you can better support your students as they complete their lab session activities.  

  • Note: Your students may need some additional support when it comes to reading their protein tests because the color change of the biruet reagent is not as vivid as the saccharide test reagent or as obvious as the translucency aspect of the lipid test that they completed yesterday.  This ambiguity can lead to a nice side conversation about their potential choices for samples to bring in for tomorrow's lab session--questions about color/flavors (sports drinks, etc.) can really spark an energetic group conversation about the best way to collect accurate data about the samples they care most about.

The Classroom Flow: Data Analysis

10 minutes

1.  Remind students to take time to discuss their data and compare it to their predictions within their lab groups.

2.  Field clarifying questions as you move around the room.  Students will typically focus on issues about clean up and the logistics of their written lab report more than anything else--the lab procedures are very detailed and you will find that the pre-lab process sets students up for success on many levels throughout the lesson series.  

  • Note:  I tend to avoid answer direct data analysis questions like, "So, is this a protein?'  I ask students to talk more about it, refer to their book or other resources and reassure them that we can check in after they've had a chance to think on the subject overnight.  The conversations they have with each other after I give that answer tend to be much deeper and richer than what would have happened had I simply answered the original question in a brief sentence.

3.  Students will be filling out their data table as you can see in this student sample, answering the summary questions on their lab document, and discussing the specifics of their written lab report responsibilities.  I find that because there is quite a bit to digest and plan for in preparation for tomorrow's culminating lab activity using samples each group brainstorms and collects for analysis, students are on task within their groups throughout the session and redirection from me as the teacher is minimal.

  • Note:  The student work sample above was representative of all of the groups' work turned in at the completion of this lab activity and group lab report discussion/writing session.  Lab reports were expected to be typed and included their pre-lab work (procedure, reagents, and hypotheses) and the data they collected and recorded as a group.  Because the most challenging test to deal with in terms of accurate data collection seemed to be the protein test that they worked with today, I made a point to encourage students to use the power of their group conversations and observations to get at their best answer for data collection and not to change their answer based upon what other groups reported out to them informally.  My goal was for them to write down their best interpretation of each test and save our data analysis as a group for tomorrow's session in an effort to reflect was researchers really do and how data is intended to start a conversation about validity and experimental design.  

The Classroom Flow: Designing and Prepping for Student Driven Exploration

10 minutes

1.  Announce that tomorrow students will be testing substances of their own choosing.  Ask each group to brainstorm four substances they will bring in for testing tomorrow.  

2.  Tell each group that they will need to get their four substances approved by you and record them on this class document

3.  Hand out this lab extension document for student groups to record their predictions for each of their chosen substances.

  • Note: Giving students time to brainstorm in class together and with you is imperative for the success of this next day's activity.  Students enjoy picking unusual things to bring in that no else will have and you can assist them in being practical yet unique.  If a group is stuck, you can offer suggestions of household items or things you have in the lab that they might be interested in discussing with their groups for inspiration.  You can also steer groups away from things that might be challenging to see color changes for or for other practical reasons such as odor to the convenience for their families to procure it/get it to class the next day.  

Now on to Day 4