A plant’s oxygen record is not the whole energy story
Original home-study reading by Math-3Zs; AI-assisted authoring.
Chapter 4 background linking observations, mechanisms and model limits.
Read before this chapter and return after its investigation. All required teaching and supplied records are available locally. Source images have their own adjacent credits.
A plant in light can photosynthesize and respire at the same time. Gross photosynthetic oxygen production differs from net oxygen exchange because consumption occurs too. A positive midday reading need not establish a positive daily balance: multiply the stated rates by their intervals before combining them.
Photosynthesis separates light-dependent energy transfer from carbon fixation. In oxygenic photosynthesis, released O₂ is traced to water, while CO₂ supplies organic carbon. Respiration connects cytosolic steps, electron carriers and membrane gradients through different mechanisms. Its summary equation is not photosynthesis’s enzyme sequence running backward.
For every pathway, keep an atom account and an energy account. Useful work needs ongoing suitable energy input even though total energy is conserved. Captured ATP depends on conditions and coupling; gas exchange alone is not an exact ATP count. Chapter investigations use controlled supplied records when direct collection is unavailable.
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Questions to carry into the chapter
How does sunlight support living systems without creating new matter?
Keep a first model, identify a measurable comparison and record a limitation to test.