Unit 4 Reflections: Macromolecules and Cellular Respiration

...and we're back from our lovely 10 day fall break today.  And jumped right in with cellular respiration.

I've had to add a lot to unit 4.  Not only did I toss in all the ecology standards, but I also needed to cover the biological macromolecules in more depth than the AMTA lesson plan suggested.

The AMTA lesson plan has students researching proteins, carbohydrates, and lipids on their own with a few guiding questions, then jumping in to comparative dissections.  My state EOC exam tests pretty darn heavily on proteins, carbohydrates, and lipids-- especially the structures and how to determine their presence in the laboratory.  Plus, our biology teachers here usually save our dissection for the last days of class after the EOC exam, since dissection and internal anatomy are not tested.  So, I ended up skipping the dissections (for now) and spending more time on the macromolecules.

Having the students research the macromolecules with guiding questions was futile.  First of all, when given the option of textbook or Google, students always go to Google.  I don't think that is necessarily a bad thing, as textbooks are becoming utilized less and less, even at the collegiate level.  But... as sophomores in high school, students can be easily led astray by misinformation online.  Especially on a topic like this, which is loaded with intimidating new vocabulary like "monosaccharide" or "polypeptide."  The whiteboard results I got, to put it simply, were really bad.  I still think it was a good activity, but I will definitely limit them to the textbook next time to avoid wasting nearly an entire class period.  Instead of dissections, we then went to the lab to practice testing for macromolecules.

Sudan IV testing for lipids

The AMTA curriculum kicks off cellular respiration with a yeast lab using Vernier Probes to measure % O2 and CO2.  The total amount of Vernier equipment my school owns:  0.  We got nothin'.  So it was back to the drawing board again.

What I decided to do was combine a yeast balloon lab with the next activity in the lesson plan, which is modeling cellular respiration with ball and stick models.  First, students created balloons with yeast and differing amounts of warm water, sugar, and air:

They measure initial diameter, set their balloons aside, while I briefly introduced them to the term "cellular respiration."  They were instructed to make a model of a glucose molecule and 6 diatomic oxygen molecules:

A glucose and a pile of O2 - not bad for students who have never taken chemistry, let alone organic chemistry. I wasn't going to split hairs on the position of the bonds in the glucose at this point. Maybe I should have.

They were then told a chemical reaction occurred between the molecules and they needed to create two new molecules.  I asked them to think about waste products, respiration, and had to prod some groups on ideas... but all of them eventually came up with CO2 and H2O.  They were then challenged to figure out how many CO2 and H2O molecules this reaction would create.  Once they were complete, they had to create an equation for cellular respiration.

Then we revisited our balloons and determined change in diameter.

We didn't get much time to discuss or create a consensus.  My plan tomorrow is to hold a board meeting with a verbal, mathematical, and diagrammatic representation of cellular respiration based on the results of the two activities.  And I guess I'll see what I get!