Eating It Up: An Introduction to Cellular Respiration

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Objective

SWBAT create a model to illustrate the chemical reactions of cellular respiration and explain the relationship between photosynthesis and cellular respiration.

Big Idea

How is your breakfast going to provide you energy to survive and thrive throughout today's Biology lesson?

Video Introduction: Connecting Breakfast and Biology

1 minutes

This video clip discusses the importance of making your Biology curriculum relevant and interesting to your students.  Cellular respiration is a complicated chemical reaction that most 9th graders could care less about, but if you can "hook" your students in by making the lesson all about them then they are more likely to open up and participate in your well-crafted lesson!

 

Hook - Breaking Down The Sugar

5 minutes

Students will watch the video below and summarize what will happen to their breakfast through the process of Glycolysis.  Students will describe the supporting details for each of thethree steps in bullet format.

  1. Investment
  2. Cleavage (yes, the students will giggle, but they are now paying attention!)
  3. Energy Harvest

Direct Instruction - Converting Breakfast To Energy!

35 minutes

The students are familiar with the chemical equation and supporting details for the process of photosynthesis through the mastery of two previous lessons, Putting The Energy Into Photosynthesis and Shedding Light On Photosynthesis.  The class always starts with studying photosynthesis first because students are familiar with the term from previous science courses and students do not seem as intimidated by the chemical equation since they are familiar with plants.  The students' work with photosynthesis helps to build their conceptual foundation and confidence to begin their study of cellular respiration since the chemical formula for cellular respiration is the reversal of the chemical formula for photosynthesis.  

Up until now, students only know the mitochondria as the "powerhouse" of the cell, but cannot provide a scientific reason for this nickname.  Students reviewed the individual cell organelles in a previous lesson, Art for Cell.  The class will use their background knowledge of the chemical equation for photosynthesis and the mitochondria, or the "powerhouse" of the cell, to dive into the complex process of cellular respiration.

As students transcribe the lecture notes, the main question will be "How does your breakfast provide energy to survive and thrive in Biology today?" Students are encouraged and reminded to make the connection between their daily life and the curriculum/chemical equation for cellular respiration.  The personal connection will provide buy-in or interest for the students since this chemical process is essential for their survival.  

Throughout the lecture notes, students will engage in class discussions regarding the details of three main components of today's lesson:

  1. Glycolysis (the breaking down of glucose)
  2. Fermentation - Lactic Acid and Alcoholic (anaerobic conditions)
  3. Cellular Respiration and the Kreb Cycle/Citric Acid Cylce (aerobic conditions)

The lecture notes are chalked full of details that cover the chemical formula for cellular respiration and provide supporting information to assist students in understanding how glucose (their breakfast) and oxygen can be converted into carbon dioxide, water, and energy.  The equation below will serve as a cornerstone for this lesson:

chemical formula for cellular respiration

Helpful Hint: Students are encouraged to take their hands and place up to their mouth and forcefully exhale.  Students are then asked what they have captured in their hands.  Students responses vary, but should include carbon monoxide, water, and heat . . . the products of cellular respiration!  Students will use this tool throughout the unit when trying to remember the products of the cellular respiration reaction.

Guided Practice - Connecting Breakfast to Snails

10 minutes

This activity can be completed as a student-led lab or a class demonstration depending on the amount of available time in the teacher's lesson plans and the available laboratory resources for the students to use. This lab exercise will exemplify the inter-relationship between plants and animals using water snails and water plants (elodea or anacharis).  

Due to the limited time in the class schedule, this activity was completed as a class demonstration in today's lesson and will be revisited in the next lesson to analyze the data and develop a conclusion.  

The remaining students in the class will be working on their Independent Practice activity while the four volunteers set up the lab demonstration.  Once the demonstration is set-up the volunteers will report back to the class what they did and explain the next steps in the lab.

To set-up the demo, the teacher will call up four student volunteers to assist in preparing the class demonstration to help students illustrate the cycling of carbon through the processes of photosynthesis and cellular respiration.   Each student volunteer will prepare their assigned test tube as follows

  • Test Tube #1: 2 pieces of water plant and 1 water snail
  • Test Tube #2: 1 water snail
  • Test Tube #3: 2 pieces of water plant
  • Test Tube #4: No living organisms (the control)

Each test tube is filled 3/4 full of water and 10 drops of Bromothymol Blue (BTB) solution (an indicator) is added.  Each volunteer will use a straw to gently (or else it will overflow) blow bubbles into their test tube until a color change is observed.  The volunteers are exhaling carbon dioxide which is acidic and will cause the BTB to turn yellow.  BTB will turn yellow if the solution's pH is less than 6 and will remain blue if the ph is 7 or above.

The tubes are left on the window sill for 24 hours.

When the students return the next day they will observe the changes in the test tubes and record their observations on the student handout.  

Please view the next lesson, "Making The Connections",  to view the student observations and conclusions.

 

Independent Practice - Tracking Your Breakfast

5 minutes

Students will use their lecture notes and textbooks as a reference to create a model that illustrates the steps in the processes of:

  1. Glycolysis: the breaking down of glucose (breakfast)
  2. Cellular Respiration or the Kreb Cycle: the conversion of pyruvic acid into carbon dioxide, ATP, and water

Students will create hand-drawn models that depict a flow chart through each chemical process.  Students will also need to develop an original narration that describes what is occurring during glycolysis and cellular respiration.  Students are encouraged to use the Cell Respiration Study Chart that summarizes the main points of the inputs and outputs of these two complex chemical reactions.

Sample of Student Work Glycolysis Narration 1 - This student's work sample demonstrates a strong understanding of the relationship between the processes of glycolysis and cellular respiration through their detailed narration.

Sample of Student Work Glycolysis Narration 2 - This student's work sample demonstrates a basic understanding of the relationship between the processes of glycolysis and cellular respiration, but lacks the details necessary to master the concept at this point in our unit of study.

Sample of Student Glycolysis Narration 3 - This student work sample demonstrates a below-basic understanding of the relationship between the processes of glycolysis and cellular respiration and the student needs remediation to break down the complex chemical processes into smaller "chunks" of information.

Sample of Student Illustration of Cellular Respiration 1 - This illustrated model does a fantastic job illustrating the chemical processes inside of the mitochondria and demonstrates great attention to detail and quality of work.

Sample of Student Illustration of Cellular Respiration 2 - This illustrated model does a fair job illustrating the chemical processes inside of the mitochondria.  The student could have dedicated more time and attention to the details of the model in an effort to understanding the complex processes of glycolysis and cellular respiration.

Close - Putting Breakfast To Work

5 minutes

As a final demonstration of cellular respiration, students will have to work their hardest to out perform the teacher.  Students are asked to select their dominant hand and then open and close it as fast as they can for as long as they can.  The teacher will continually encourage them to go fast and not give up.  After about 30 seconds even the toughest of students is wincing in pain in their forearm muscles.  The teacher then asks the students what is going on and why does such a simple task hurt after awhile.  Student volunteers are asked to provide their best guess.  The target response is lactic acid fermentation has built up in the forearm muscles because that specific muscle group has used all of the oxygen and glucose that is available.  

Family Involvement: Students are encouraged to go home and ask their parents to participate in the same activity and see if they can provide the scientific explanation as to why opening and closing your hand (really fast) begins to hurt after awhile.  This is another opportunity for students to get their families involved with what they are doing in Biology!

Students will complete their illustrated flow charts and narrations for homework.  Students are also encouraged to share their illustrations with their parents and explain the chemical process of cellular respiration.  Students are also warned that their parents may not understand and they need to explain the process as, "What happens to your breakfast and how it gives you energy to survive and thrive throughout the day."

Examples of student work can be found in the section above.