Biology Lesson

Energy Cycles: Photosynthesis & Cellular Respiration in Conversation

Shared by A STEM Educator

9th Grade5E Model50 min

Learning Objective

Students will be able to explain how light-dependent and light-independent reactions in chloroplasts produce glucose and oxygen, how glycolysis and aerobic respiration in mitochondria extract ATP from glucose, and how carbon atoms are conserved as they cycle between CO₂, glucose, and CO₂ again.

Lesson Overview

Students trace the cyclical flow of carbon and energy between photosynthesis and cellular respiration, modeling how chloroplasts and mitochondria are metabolic partners. The lesson builds from the overall equation to the molecular machinery of each reaction stage.

Materials

Paper (blank or lined)
Pencils
Whiteboard and markers

Scaffolded Task Progression

1Task 1

A student says: 'Plants get their food from the soil, just like animals get food by eating.' Do you agree or disagree? Use the idea of carbon atoms to support your answer in 2–3 sentences.

2Task 2

Using your carbon round-trip diagram, answer:
(a) Count all carbon atoms on both sides of the equation

6 CO_{2} + 6 H_{2} O ⇌ C_{6} H_{12} O_{6} + 6 O_{2}

. Are they equal? What law does this demonstrate?(b) Which molecule carries the carbon atoms — H₂O or CO₂ — into glucose during photosynthesis?(c) Which molecule carries carbon atoms OUT of the cell during respiration?

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