Cellular Respiration - Direct Instruction

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Objective

Students will be able to read and understand the cellular respiration equation.

Big Idea

Reading a chemical formula can seem like a different language.

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Purpose of Lesson:

 The purpose of this lesson is to help students deconstruct and understand the cellular respiration equation.  This understanding is vital to long term understanding of the concept so that they will be able to read and understand the equation after they have forgotten the specific reactants and products.

Major Strategies to Watch for:

1) Shared reading- A reading strategy to use that will help students gain the skills necessary to read high level texts on their own.

2) Writing to think- A writing strategy that allows students to write without fear, solidifying their understanding and coming to new conclusions.  

Ready. Set. Engage!

5 minutes

Learning Goal: Read and understand the cellular respiration equation.

Opening Question: If photosynthesis was about making food, what do you think cellular respiration is about?

Students record their opening question on their learning goal sheet and are ready to start class 3 min after the bell has rung.  I reward students who get started early with ROCK STAR SCIENTIST tickets.  

Follow the links to learn more about the beginning of class strategies and ROCK STAR scientist tickets.   

Hook

5 minutes

I start the lesson by putting up this picture and asking the students a series of questions.  Sometimes, I even bring in fruit and crusty bread for the students to eat.

1. Where does the bread come from?

2. Where does the fruit come from?

3. How did the plants make the food?

4. What ingredients did the the plant use to make the food?

Then I write the equation for photosynthesis on the board and ask the students to do a writing to think about photosynthesis.

Their job is to put down everything they know about photosynthesis in 3 min.   Writing to think is a great way for students to pull up ideas from their brain and make new connections.  

At the end of the 3 minutes I use the equation of photosynthesis on the board to remind students of the following:

  • Photosynthesis has reactants and products.
  • The purpose of photosynthesis is to make glucose which can later be made into sugar and starch like found in bread and fruit.
  • The energy that photosynthesis uses is sunlight. 

Focus

5 minutes

Today we are doing a shared reading on reading chemical equations.  I'm choosing this strategy because my students struggled with understanding the chemical equation in the previous unit and I want to give them a strong foundation for this unit.  

Shared reading is a great reading strategy to use when your goal is not only to help students with specific content, but also help them read a specific genre type.  In this situation, we are "reading" chemical formulas.  The big idea of shared reading is to gradually dig deeper and deeper into a complex text over a number of days, all the time exposing your own thinking to the students.  A sample plan for shared reading might look like this.

Day 1- Preview the text and notice text features.

Day 2- Comprehend the text using questioning, determining importance, visualization, or clarifying.

Day 3- Extend the text using summation, inference, or synthesis.

For this lesson, my job is simply to expose them to the text and my thinking, while allowing them to do some thinking. 

First, I put the equation on the board.  I try also to have the equation at the students' tables so that they can have a choice of where to look. 



Then I talk about the text and show the students what I am seeing and noticing.  There is a screencast below to show what this might look like. 

Unable to display content. Adobe Flash is required.

 

When I am done with my noticingings.  I ask the students to compare this equation to the photosynthesis equation they already know and make some connections.  I ask the students to write their connections on post -its and then I collect them.  This information will be used to make the anchor chart.   

Guided Practice

10 minutes

The purpose of this section is to as a class get some practice in adding up the amount of atoms in the formula.  The reason I do this is to make a connection that you aren't creating any matter...you are simply rearranging it.  This is the same activity that my students did with photosynthesis.  I find that there is some real power in repeating the activity because students are so much more fluent at the skills that they understand the content more.  

I really enjoy being a game show host in my class.  This brightens the darkest and most serious lesson with some light hearted fun.  Sometimes, I even get out my daughter's toy microphone and really have a blast.  For this lesson I call the game,  COUNT THE ATOMS.  

I tell students that they are all contestants in a new game called COUNT THE ATOMS.  I have them pick up a whiteboard for every pair of partners and a dry erase marker.  Before we play the game I remind students about the words atoms and molecules.  

I start with the sugar molecule because it doesn't have a coefficient.  I ask the students to write down the number of Carbon atoms in one molecule and hold their boards up.  It is instantly apparent to me whether the students understand or not. Then we do Hydrogen and Oxygen. 

Next, I remind them about the coefficient.  First, I ask them to guess how many oxygen atoms are in 6CO2.  They put their numbers down and generally most of them are wrong.  I use this opportunity to draw the CO2 molecule and then draw 6CO2.  Once they see this they get it right away and I remind them about the distributive property in math.

Then we go back to the game show and practice counting the atoms for the rest of the equation.  

For the final problem I ask them to add up all the atoms in the reactant side and all the atoms in the product side.  This is a more difficult task for them.  I pull up the students that had the right answers and ask the rest of the class to see what they notice.  At this point we briefly talk about how there are the same number of oxygen atoms on each side, the same number of carbon atoms on each side and the same number of hydrogen atoms on each side.  I tell them that this is important because we aren't creating anything with photosynthesis...we are just rearranging. 

Below are some pictures of student boards.

Collaborative Practice

20 minutes

The purpose of this section is to give students a chance to collaboratively work together to read and understand the equation.  This is the second time my students have done a flow map for a chemical equation.  The first time was pretty rocky, but the students did much better this time.

I start this section by teaching the students how to make a flow map.  

I demonstrate how to do a flow map by making a flow map of my morning.  I try to make this funny by throwing in comments like, and then my daughter had a tantrum, or then my son forgot his homework.  

Once students understand how to make a flow map I tell them that their job is going to be to use the equation and make a flow map of the events in the equation.  For example, the first event would be, cell takes in sugar.   

Once students understand I let them work together to make their flow maps in their notebooks.  If the finish quickly I encourage the students to add color and pictures to make their maps even better.

When the students are finished, I ask them to compare their flow maps of photosynthesis and cellular respiration. I walk around and listen to their conversations until I hear a student say that the equations are opposites.  At that point I stop the class and elevate that statement to see if all students agree with it.  We finish this conversation  with the understanding that photosynthesis and cellular respiration are processes that are connected. 

Independent Practice

7 minutes

We finish this period with another writing to think. This time the prompt for the students is "Use the cellular respiration equation to explain the process of cellular respiration." I give the students 3-4 minutes of writing time. It is important to give the students enough time to write, because generally students will be processing while they write and it takes a while for the ideas to float to the top.   

 

My students have a writing to think notebook that goes in their folders. It is simply five pieces of blank paper stapled together with a piece of colored paper on top. This is a great way to have ongoing formative assessment as well as build fluency in writing.  

Closure

3 minutes

Closing Statement: "Today, we looked at how to read the equation for cellular respiration.  Tomorrow we will be trying to understand the main idea of photosynthesis." 

Closing Question: "How do you think cellular respiration relates to your life?"

Closure depends greatly on timing and is not as easy to plan in advance as opening.  You can find more information about how I manage closure here.