Lesson Plan

• Describe the overall stages of aerobic respiration and locate the link reaction.
• Explain the conversion of pyruvate to acetyl‑CoA by the pyruvate dehydrogenase complex.
• Identify the key enzymes (E1, E2, E3) and cofactors involved in the link reaction.
• Illustrate why oxygen is essential for the continuation of the link reaction.
• Predict the products generated per glucose molecule during the link reaction.

• Projector and screen for diagram slides
• PowerPoint/PDF handout of the link reaction diagram
• Whiteboard and markers
• Student worksheets with fill‑in tables
• Printed mitochondrion diagram or model (optional)
• Quiz cards for quick recall

Begin with a quick think‑pair‑share: where does the energy from glucose go after glycolysis? Review that glycolysis ends in pyruvate in the cytosol and preview today’s focus on its fate in the mitochondria. Students will know they can explain how oxygen availability influences this step.

1. Do‑now (5') – Students answer a short question on glycolysis end‑products on the board.
2. Mini‑lecture (10') – Present the link reaction overview, location, and equation using slides.
3. Interactive diagram (10') – Using the projected mitochondrion diagram, students label the pyruvate carrier and the three enzyme components.
4. Guided practice (10') – Worksheet where pairs write the step‑by‑step transformation of pyruvate to acetyl‑CoA, including cofactors.
5. Concept check (5') – Quick quiz cards: “What would happen if oxygen were absent?”.
6. Summary discussion (5') – Teacher recaps key points and links to the upcoming Krebs cycle.

Total time: 45 minutes.

Summarize that the link reaction bridges glycolysis and the Krebs cycle, producing acetyl‑CoA, CO₂ and NADH, and requires oxygen indirectly. Students complete an exit ticket writing one sentence on why oxygen is critical. For homework, assign reading of the Krebs cycle and a worksheet to map the flow of carbon atoms.