Science · Grade 7

Active learning ideas

Mitochondria and Cellular Respiration

Active learning lets students connect abstract cellular processes to observable results. When students see yeast balloons inflate or measure their own pulse after exercise, they grasp how mitochondria convert food into usable energy. Hands-on work makes the invisible visible and the complex concrete.

• Ontario Curriculum Expectations
• MS-LS1-2

• 20–35 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Simulation Game
• 30 min · Small Groups

Lab Demo: Yeast Balloon Respiration

Mix yeast, sugar, and warm water in a bottle, stretch a balloon over the mouth, and place in warm spot. Students observe and measure balloon inflation from CO2 byproduct over 20 minutes. Compare trials with and without sugar to infer glucose's role.

Explain what causes a cell to stop functioning if the mitochondria are damaged.

Facilitation Tip

During the yeast balloon lab, circulate to ask groups to predict what will happen if they skip the sugar or the yeast, reinforcing the need for both reactants.

What to look for

Provide students with a scenario: 'Imagine a cell is deprived of oxygen. What happens to ATP production and why?' Ask them to write a short explanation, naming the key organelle involved and the process that stops.

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Activity 02

• Simulation Game
• 25 min · Pairs

Pairs: Cell Model Builds

Provide clay or beads for students to construct two cell models: one muscle cell with many mitochondria, one skin cell with few. Pairs predict and discuss activity differences, then present to class. Use diagrams to label respiration steps.

Analyze the relationship between cellular respiration and the energy needs of an organism.

Facilitation Tip

When pairs build cell models, ask them to explain why their muscle cell model has more mitochondria than their skin cell model, using function to justify design.

What to look for

Display images of cells from different tissues (e.g., muscle cell, skin cell). Ask students to identify which cell type likely has more mitochondria and to justify their answer based on the cell's function and energy needs.

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Activity 03

• Simulation Game
• 35 min · Whole Class

Whole Class: Pulse and Exercise Challenge

Students measure resting pulse, do jumping jacks for 1 minute, then remeasure. Class graphs data to link increased heart rate to higher cellular respiration demands in muscle cells. Discuss ATP needs.

Predict the impact on an organism's activity level if its cells had fewer mitochondria.

Facilitation Tip

Before the pulse and exercise challenge, model how to measure pulse at the wrist and neck so students collect accurate data during the activity.

What to look for

Pose the question: 'If a person's cells had significantly fewer mitochondria, how would their daily activities, like walking to school or playing sports, be affected?' Facilitate a class discussion where students connect cellular energy to organismal performance.

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Activity 04

• Simulation Game
• 20 min · Individual

Individual: Respiration Rate Predictions

Students list organisms by activity level, predict relative mitochondria per cell, and justify with respiration equation. Share predictions in quick class huddle and refine based on feedback.

Explain what causes a cell to stop functioning if the mitochondria are damaged.

Facilitation Tip

For the respiration rate predictions, review sample responses together so students see how to connect cellular processes to real-world examples.

What to look for

Provide students with a scenario: 'Imagine a cell is deprived of oxygen. What happens to ATP production and why?' Ask them to write a short explanation, naming the key organelle involved and the process that stops.

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

A few notes on teaching this unit

Teach this topic by moving from observable phenomena to microscopic processes. Start with the yeast experiment to show energy release, then use models to visualize mitochondria in different cells. Avoid starting with textbook definitions, which can make the process seem static. Instead, let students discover the steps through guided inquiry and peer discussion. Research shows that connecting cellular respiration to organismal energy demands builds deeper understanding than isolated memorization.

Students will explain how mitochondria produce ATP, link respiration rates to energy demands, and justify why cell function depends on healthy mitochondria. They will use models, data, and discussions to show their understanding of cellular respiration in organisms.

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Watch Out for These Misconceptions

• During the Lab Demo: Yeast Balloon Respiration, watch for students who assume the balloon inflates because yeast 'create' energy.

  Use the lab’s discussion to point to the sugar container and ask, 'Where did the gas in the balloon come from?' Lead students to trace the carbon atoms from glucose to carbon dioxide, emphasizing energy transformation rather than creation.

• During Pairs: Cell Model Builds, watch for students who confuse breathing with cellular respiration.

  Ask each pair to label their model with both the lung diagram and the mitochondrial cutaway, then trace the path from air to ATP using arrows. Have them explain the difference to another pair before sharing with the class.

• During Whole Class: Pulse and Exercise Challenge, watch for students who think all cells have mitochondria in equal numbers.

  After data collection, display a table of cell types and their mitochondrial counts. Ask groups to revise their cell models to reflect the data, then justify their changes using energy demands from the pulse measurements.

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Methods used in this brief

• Simulation Game