Cellular Respiration: The Energy Release in Every Cell

Estimated Time: 45-60 minutes

Materials: Internet-connected device, Cellular Respiration simulation, student handout.

Part 1: Engage (Anchoring Phenomenon)

When you exercise hard — whether it is a sprint, a heavy set of squats, or a long run — your muscles begin to burn and you start breathing heavily. You might have noticed that the harder you push, the faster and deeper you breathe.

Initial Reflections:

Why does your breathing rate increase when you run? What is your body trying to bring in more of?
Where does the energy for your muscles actually come from — what is being “burned” inside your cells?
What “need to know” questions do you have about how food molecules get converted into usable energy?

Part 2: Explore (Simulation Investigation)

You will use the Cellular Respiration simulation to investigate how glucose and oxygen are used inside the mitochondria of your cells to produce energy.

Simulation Controls:

Glucose Molecules slider (C6H12O6) — controls how many glucose molecules are available.
Oxygen Molecules slider (O2) — controls how many oxygen molecules are available.
1. Update Inputs button — loads your chosen molecule counts into the mitochondrion model.
2. React button — triggers the cellular respiration reaction inside the mitochondrion.
Lactic Acid Pathway toggle — switches between aerobic (oxygen present) and anaerobic (no oxygen) pathways.
Atom Count Panel — displays the number of carbon (C), hydrogen (H), and oxygen (O) atoms before and after the reaction.
ATP Readout — shows the number of ATP (energy) molecules produced.
Chemical Equation Panel — displays the balanced equation for the reaction.

Investigation A: Baseline — Aerobic Respiration

Set Glucose Molecules to 1.
Set Oxygen Molecules to 6.
Ensure the Lactic Acid Pathway toggle is OFF (Aerobic mode).
Click 1. Update Inputs, then click 2. React.
Observe the mitochondrion model and the output panels.

Record your observations in Data Table A below.

Data Table A: Baseline (Aerobic, 1 Glucose + 6 O2)

Observation	Value
Reactants (Inputs)	1 C6H12O6 + 6 O2
Products (Outputs)
ATP Produced
Carbon atoms before reaction
Carbon atoms after reaction
Hydrogen atoms before reaction
Hydrogen atoms after reaction
Oxygen atoms before reaction
Oxygen atoms after reaction
Are any atoms created or destroyed?

Investigation B: Varying Glucose

Keep Oxygen Molecules at 6 and ensure the Lactic Acid Pathway is OFF. Change the Glucose Molecules slider and record the results.

Glucose Molecules	O2 Molecules	ATP Produced	Products Formed
1	6
2	6
3	6

Questions:

What happens to the ATP produced as you add more glucose?
Does the amount of CO2 and H2O produced increase, decrease, or stay the same?

Investigation C: Varying Oxygen

Keep Glucose Molecules at 1 and ensure the Lactic Acid Pathway is OFF. Change the Oxygen Molecules slider and record the results.

Glucose Molecules	O2 Molecules	ATP Produced	Products Formed
1	6
1	4
1	2
1	1

Questions:

What happens to ATP production as oxygen decreases?
At what point does the reaction stop producing CO2 and H2O?

Investigation D: Anaerobic Pathway (The “Burn”)

Click Reset.
Set Glucose Molecules to 1.
Set Oxygen Molecules to 0.
Turn the Lactic Acid Pathway toggle ON.
Click 1. Update Inputs, then click 2. React.
Observe the output.

Observation	Value
Reactants (Inputs)	1 C6H12O6 (no O2)
Products (Outputs)
ATP Produced
New molecule produced (not seen in aerobic)

Questions:

How does the ATP yield of the anaerobic (lactic acid) pathway compare to the aerobic pathway?
What new molecule appears as a product? This molecule is associated with the “burning” sensation in muscles during intense exercise.

Part 3: Explain (Sensemaking)

Using your data from the simulation investigations, answer the following questions:

Matter Rearrangement: In the aerobic reaction (1 C6H12O6 + 6 O2), the reactants contain 6 carbon atoms, 12 hydrogen atoms, and 18 oxygen atoms. What are the products, and do the atoms rearrange or are they created/destroyed? Use your atom count data as evidence.
Energy Transfer: The chemical equation for aerobic cellular respiration is: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP) Where does the energy to make ATP come from? (Hint: Think about breaking bonds in glucose and forming new bonds in CO2 and H2O.)
The Role of Oxygen: Compare the ATP yield from Investigation A (6 O2) with Investigation D (0 O2). Why is oxygen so critical for maximizing energy production?
The “Burn”: Based on your data, what molecule is produced during anaerobic respiration that is NOT produced during aerobic respiration? How might this molecule relate to the muscle “burn” you feel during intense exercise?
Breathing Connection: How does your increased breathing rate during exercise connect to what you observed in the simulation? What is your body trying to deliver to your cells?

Part 4: Elaborate/Evaluate (Argumentation & Modeling)

Final Task: Construct a Scientific Explanation (CER)

Prompt: When you exercise hard, your muscles burn and you breathe heavily. Using evidence from the Cellular Respiration simulation, explain why your breathing rate increases and what causes the burning sensation in your muscles. In your explanation, describe how matter is rearranged and how energy is transferred during cellular respiration.

Your explanation must include:

Claim: A clear statement answering the question about why breathing increases and muscles burn.
Evidence: Specific data from your investigations (Investigations A-D), including ATP counts, atom counts, and product molecules observed.
Reasoning: Explain HOW the evidence supports your claim. Discuss:
- How matter (atoms) is conserved but rearranged into new molecules during the reaction.
- How the energy in chemical bonds is released and captured as ATP.
- The difference between aerobic and anaerobic pathways and why the body uses each under different conditions.

Scoring Rubric

Component	3 - Exemplary	2 - Proficient	1 - Developing	0 - Not Present
Claim	Clearly states the relationship between breathing rate, muscle burn, oxygen delivery, and anaerobic vs. aerobic respiration.	States a correct but incomplete claim connecting breathing and muscle burn.	States a claim with minor inaccuracies.	No claim stated.
Evidence	Cites specific, quantitative data from at least 3 investigations (ATP counts, product molecules, atom counts).	Cites data from 2 investigations with some specifics.	Cites data from 1 investigation or provides vague references.	No evidence provided.
Reasoning	Thoroughly explains matter conservation, bond energy transfer, and the aerobic/anaerobic pathway difference using simulation evidence.	Explains 2 of the 3 reasoning components with some connection to evidence.	Explains 1 reasoning component or reasoning is disconnected from evidence.	No reasoning provided.

Teacher Notes

NGSS Alignment

Performance Expectation: HS-LS1-7. Use a model to illustrate that cellular respiration is a chemical process whereby the bonds of food molecules and oxygen molecules are broken and the bonds in new compounds are formed, resulting in a net transfer of energy.
Science and Engineering Practice (SEP): Developing and Using Models. Students use the Cellular Respiration simulation as a model to illustrate the relationships between reactants and products, track matter and energy, and predict outcomes under different conditions (aerobic vs. anaerobic).
Disciplinary Core Idea (DCI): LS1.C: Organization for Matter and Energy Flow in Organisms. As matter and energy flow through different organizational levels of living systems, chemical elements are recombined in different ways to form different products. Cellular respiration is a chemical process that releases energy from food molecules.
Crosscutting Concept (CCC): Energy and Matter. Changes of energy and matter in a system can be described in terms of energy and matter flows into, out of, and within that system. Students track carbon, hydrogen, and oxygen atoms to demonstrate conservation of matter, and track ATP to demonstrate energy transfer.

Evidence Statement Mapping (HS-LS1-7)

Student work will demonstrate the following evidence statements:

1. Components: Students identify the components of the model (glucose, oxygen, carbon dioxide, water, ATP) and describe how bonds are broken and formed.
2. Relationships: Students describe the relationships between reactants and products, noting that CO2 and H2O are produced from C6H12O6 and O2, and that energy is released because the bond energy of the products is greater than the bond energy of the reactants.
3. Connections: Students explain how the chemical reaction releases energy as matter is rearranged, how bonds are broken and formed, and that both matter and energy are conserved throughout the process.

Expected Outcomes

Aerobic (1 glucose + 6 O2): 6 CO2 + 6 H2O + ~36 ATP produced. Atoms are conserved (6C, 12H, 18O on both sides).
Anaerobic (1 glucose + 0 O2, lactic acid pathway): 2 Lactic Acid (C3H6O3) + ~2 ATP produced. Much less energy yield; lactic acid accumulation causes muscle burn.