Sickle Cell Anemia Investigation: Day 5

Today did not go too well. I must remind myself that it is quite a lot for students to jump from DNA to mRNA to Protein Shape & Function to Cell Shape to bodily function. Still, I think today should have worked much better than it did.

We started with a video by BioVisions at Harvard titled Cellular Visions. It shows how many different types of proteins function in a cell.

It also includes a scene of actin polymerizing which I could pause and discuss. Because It would play into our class discussion.

Then we reviewed that cells shape helps them to perform their function and that their shape is determined by a sequence of amino acids. I told several other protein ‘stories’. I then ended with a visual from Utah Genetics that shows cell size and scale so that I could compare a red blood cell and a hemoglobin protein. I still have many students who cannot interpret that cells are much larger than proteins.

Next, I tried to do a hands on activity with the students that I got from HHMI titled How Do Fibers Form. I think the lesson should work but I couldn’t get it to click. I had lots of blinking and phone issues instead of engaged hands and minds.

Essentially, students take cut out paper models of hemoglobin and they try to piece them in a cell to see how the proteins interact and determine the shape of the cell.

Normal Hemoglobin is “closed” when it is carrying an oxygen molecule. That is, it has no open pocket to accept DNA. So the proteins simply bounce off one another .

I pulled up David Goodsell’s Molecule of the month blog to show the students the behavior of this hemoglobin molecule.

I physically move my body to imitate the hemoglobin in a closed configuration. By pretending to catch oxygen.

On the other hand when an oxygen is not bound to the heme group of hemoglobin it enters an “open” configuration.

This molecule is ready to accept an Oxygen. Thus, it is ‘open’ I slink my body around the room like a catcher with his mitt open and ready to receive a ball. *don’t you wish you had a picture of that 🙂

We can model this with a piece of paper that has a hole punch to show that it is open.

I ask the students to show how these proteins might interact if they were bouncing around a cell. None of my students got this at all…There were literally crickets chirping in my Leopard Gecko cage folks… pppsssssssth 🙁

One or two students suggested that they may clump together.

Next, I had them manipulate models of hemoglobin that had been mutated.

Actually, several of the students started stringing them together… but none (literally 0/111) of them put together that this growing chain of proteins could actually push on the cell membrane to change the shape.

some students got this idea that the proteins would clump together
No students had the notion that the proteins would change the shape of the cell.
None of my students got this far.

I actually did a clearer example with better models that I had printed off.

These ‘normal’ hemoglobins wouldn’t clump
This mutated protein has a pocket for binding to occur in.
Here they could really see how the proteins would stack up to form a polymer fiber that pushes out the cell.

By the last hour I simply just showed them how this could work with my overhead projector. Then we went outside with the last 10 minutes of class and played hacky sack.

I am going to try again on Monday.

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