Cell Respiration, part 2

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Objective

Students will examine how exercise affects carbon dioxide production.

Big Idea

Prolonged exercise relies primarily on aerobic metabolism.

Warm-Up

5 minutes

Warm-UpInstruct students to examine the image.  Ask, “Which row correctly identifies the lettered substances in the process? 

This question challenges students to both activate prior knowledge about cell respiration and also figure out how to read and interpret information in a table.  Many students will struggle with the format of the response choices even though they might have been able to identify the correct response had it been presented in narrative form. 

Giving students opportunities to experience different formats better prepares them for variations of responses that they will likely see on summative assessments. 

If students are noted to need assistance with the interpretation of the table, provide guidance on how to read the table without giving students the correct response.  Allow 2-3 students to respond to the question.  Ask students to explain their answer choice.  This practice of requiring an explanation for answer responses helps students think about their own thinking and sometimes help them correct themselves.

Concept Review

10 minutes

Display this graphic organizer on a LCD projector.  Ask, “What process is depicted?”  Ask them how they know.  Look for students to identify a number of reasons that lets them know that the image is cell respiration.  For example, they could note that the image shows a mitochondrion, which lets them know that the process is cellular respiration.  Or, they could note that the process has 3 reactants and 2 products, which suggests that the reaction is cell respiration.

Explain that the first 6 numbered blanks are intended to reflect the reactants and products of the chemical equation for respiration.  Think aloud as you identify the term that fits each of the first 3 numbered blanks on the organizer. It’s important to share your thinking so that students will be able to see how you process the information that has been taught in order to complete the task.  Build in a few “almost” mistakes that you self-correct so that students will see how to evaluate their own responses to ensure that their thinking lines up with what they’ve learned before they commit to a response.

After modeling the first few answers, give students to 5 minutes to complete the remaining numbered parts of the organizer.  Allow students to work with a seat partner to complete the task. Walk around the room as students are working to note comments that suggest clear understanding or misconceptions.  Make a note to clarify any misconceptions that are heard while walking around.  After the allotted time, review the correct responses with the class using a digital pen to write the correct responses on the organizer that is displayed on the LCD projector.  This review helps reinforce key concepts from the prior lesson, cell respiration, part 1 before students conduct the  lab.          

Introduce New Material

20 minutes

Share a brief video clip, When Muscles Give Up then ask students to recall a time when they had to participate in rigorous exercise for an extended period of time.  Ask students to share what their muscles felt like or tell what type of advice coaches gave them. Allow 2-4 students to respond and stop the responses once someone shares a similar comment to one of these two comments “The coach told me to stand upright and breathe through my nose” or “The coach told me to stand up and put my hands over my head.” 

Pause for emphasis, and then ask students to think of possible reasons why a coach might give these instructions.  Take 4-5 comments from the group.  Quickly jot each reason on the board.  Engage the entire class in the discussion by asking students to raise their hand to show agreement with the comment that reflects their opinion. Look for students to recognize that there is a relationship between muscle function, oxygen intake and carbon dioxide production. 

Inform students that today we are going to examine how exercise affects carbon dioxide production.

Guided Practice

10 minutes

Before students perform the close read of the lab, display a summary of  cell respiration lab using a LCD projector.  Provide both verbal and visual instructions to address the needs of different learner types. 

Explain that bromthymol blue is an indicator.  Allow students to tell you what they think an “indicator” does.  Look for students to identify that an indicator “shows”.  Affirm that bromthymol blue is an indicator that tests for the present of carbon dioxide.  Explain that the bromthymol blue will change color form blue to yellow in the presence of carbon dioxide.  Demonstrate the correct procedure for blowing into a test tube of bromthymol blue.  Show students how to blow gently into the test tube, making sure that you point out that the hand should cover the top of the test tube as you blow into the solution.  Make sure that students know that the term, exhale means to blow air out of the body.  Remind students of the safety procedures for the class and the requirement that students wear safety goggles at all times while conducting the procedure.

Inform students that the lab will be conducted in small groups of two, with each student completing his/her own lab analysis and conclusions.  Decide beforehand if you will assign the student groups or whether you will allow students to select their own groups.  Because this lab involves close work with a chemical, I assign the work groups to eliminate the potential for “horseplay” among students.

Review the two roles, recorder and lab subject:

Recorder

–       Records time it takes for the solution to change from blue to yellow in each of the two trials

–       Adds the data to the Group Data Table

Lab Subject

–       Runs in place or performs jumping jacks for the timed period

–       Blows into the test tube after each exercise period

Distribute copies of an  endurance and muscle fatigue article.  Instruct students to perform a close read of the article after completing the first 4 questions in the analysis/conclusion portion of the lab.  Inform students that the information in the article will help them respond to the analysis questions that follow the lab procedure.  

         

Independent Practice

20 minutes

Distribute copies of the Cellular respiration Lab.  Instruct students to take 5-7 minutes to perform a close read of the lab.  Instruct them to write down any questions that they have as they read the lab.  The close read strategy allows students to read with a purpose, in this case to learn what the lab will require them to do and know. At the end of the allotted time, give students an opportunity to ask their questions so that you can provide clarification and eliminate confusion about the procedure.

Instruct students to formulate a hypothesis before beginning:

I predict that exercise will __________________________ (increase/decrease/have no effect) on the rate at which Carbon Dioxide is produced.

Walk around while students are conducting the lab to look for appropriate safety procedure (wearing goggles, no horseplay, etc…).  Listen to student comments and redirect their thinking with inquiry questions, as needed.

Close

5 minutes

Allow students to share their responses to the question, “What is the benefit of athletic endurance for an athlete?

This is a higher level question that may stump students.  However, it's a good assessment of the depth of learning and the connections students made as a result of the instruction.

Be prepared to guide students to identify that  endurance athletes build stronger hearts that allow oxygen to get to the muscles more efficiently, which also increases the removal of waste and carbon dioxide from the muscles.  

A guiding questions might be:

Does an athlete have a more efficient heart?  If so, what's the benefit of a more efficient heart when we consider the process of cell respiration?