The Building Blocks

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Objective

As a basis for understanding cell processes, students will be able to identify the four macromolecules that make up the building blocks of life.

Big Idea

All organisms are composed of the four macromolecules.

Note to Teachers

The Cell Processes unit is the second part of my Cells 'R Us project based learning experience (PBL). Once the students are familiar with the structure of cells, we move on to how cells work. The lessons in this sequence are based on the "need to know's" created by the students (with guidance) for the Cells 'R Us project.

The complete sequence I use for the Cells 'R Us project is:

Hook

5 minutes

I begin this lesson by displaying the first slide of the presentation, and ask the students to Think-Pair-Share, "What do all of these have in common?":

We agree that they are all alive and made of cells. I then state, "Would it surprise you to know that they are also all made of four basic molecules and just a handful of elements?", and ask, "What do you think those could be?". Students are given another couple of minutes for a think-pair-share.

To add even more of a bang to what was just discussed, I tell the students that four basic molecules are responsible for everything they are about to see, and present the Inner Life of the Cell, a BioVisions video from Harvard (embedded in the second slide of the presentation). If you are not familiar with this famous video, I'd suggest you watch it first. There are several versions, some of them annotated. This one is meant to be beautiful and inspiring. I chose it not for its instructional value, but to encourage a sense of wonder in the students. Very few people would find studying macromolecules particularly exciting, but when you can actually "see" them in action, you can't help but want to know more. While watching the video, you will hear the students begin to ask questions like "What is that? Is this actually real? You mean that that happens inside our cells?" Without prompting, you set the stage for deep interaction with the material.

There is also a TEDTalk by the animator (XVIVO Scientific Animation).

Presentation

40 minutes

I present the organic compounds slideshow.

In the slideshow I have indicated key ideas in red. I do this to avoid students trying to copy everything down. Although this could become a crutch, I have found that students at this level are still not very adept at identifying key points on their own. As the year progresses, I slowly remove the indicators, and instead hold conversations that begin with, "What is the important information that can be taken away from this slide?". This is intended to gradually release students to construct their own explanations (Practice 6 Constructing Explanations and Designing Solutions - "Students are expected to construct their own explanations, as well as apply standard explanations they learn about from their teachers or reading.")

In slide 4, I take the time to discuss the term "organic". One of my pet peeves as a scientist is the public confusion about this term. I try to remedy this confusion in my own little way by pointing this out. For example, "Alcohol, nicotine and plastics are all organic compounds. Does that mean that they are good your you?" and "Corn grown with all the pesticides you can think of as organic". We also talk about coming up with a better term for products labeled "organic". Although this is a battle that I know I have already lost (the USDA has specific requirements to label foods "certified organic"), it is always fun to keep trying.

There is a lot of information in the presentation that the students need to engage with. To break it up, I include short clips from the ""Molecules Gone Wild (Bio Style)" - Gangnam Parody", which are linked in the presentation. 

The "questions to ponder" in slide 24 lead to a whole class discussion, in which we talk about a balanced diet, as well as about sugars vs. fats as sources of energy. Listen in as a student gives his answer to "Why do you get a sugar high but not a fat high?"


Closure

8 minutes

To close the lesson, I present the complete "Molecules Gone Wild - Bio Style" video. The students really get a kick out of this one, so don't be surprised if they start dancing. 

Turning on closed captioning - CC - helps to stress the content. Here's how to do it on the YouTube site:

The exit ticket or deliverable for the day is a post-it note on my reflective chart ("My Aha moment..." - "One thing I'm still thinking about..." - "My learning stopped when..."). This chart is posted at the front of the room, and gives me a quick reference into student thinking and attitudes in the classroom.