Sugar Factories & Energy Engines: Photosynthesis and Cellular Respiration

Shared by A STEM Educator

7th Grade5e-learning-cycleMS-LS1-6, MS-LS1-7, MS-PS3-345 min

Learning Objective

Students will construct and evaluate models of photosynthesis and cellular respiration to trace the flow of matter (carbon, oxygen, water) and energy through living systems, applying these concepts to agricultural and biofuel engineering contexts.

Lesson Overview

Students investigate how plants manufacture sugar using light energy (photosynthesis) and how living cells release that stored energy (cellular respiration), connecting both processes to real-world biofuel engineering and greenhouse crop optimization.

Materials

Spinach leaves (fresh, 10–12 per group)
Plastic syringes (10 mL, no needle, 1 per group)
Sodium bicarbonate solution (0.2% baking soda in water)
Liquid dish soap (1 drop per 300 mL solution)
Clear plastic cups or beakers (250 mL)
LED grow lights or desk lamps (varying distances: 5 cm, 15 cm, 30 cm)
Stopwatch or timer (per group)
Molecular input/output sorting cards (printed, 1 set per group)
Carbon atom tracking worksheets
Closed ecosystem mesocosm jars (1 L mason jars with lids, soil, small plants, isopods)
Whiteboard markers and VNPS boards (or large chart paper)
Colored pencils (red, blue, green, black)
Data recording sheets
Tape and scissors

Scaffolded Task Progression

1Task 1

Warm-Up Prediction: You are about to place infiltrated spinach leaf discs (filled with liquid, no air) into a sodium bicarbonate solution under a bright light. The discs currently sink. Predict: Will the discs float, sink further, or stay the same after 8 minutes under light? Write your prediction AND explain the mechanism you think is responsible.

[ Interactive graph / diagram — available in the full lesson ]

2Task 2

Floating Leaf Disc Lab — Data & Pattern: Run the Floating Leaf Disc Assay at your assigned light distance. Record your floating disc counts in the table below, then plot your group's data on the class graph on the VNPS board.

After all groups share, answer: What pattern do you see between light distance and the number of floating discs? Use evidence from the class data set in your answer.

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