Photosynthesis and Oxygen

Measuring oxygen to assess how photosynthesis is affected by changes in the amount of light available to plants.


PASPORT Oxygen Gas Sensor (PS-2126A)

PASPORT Oxygen Gas Sensor (PS-2126A)

Lab Summary

Students will assess how changes in the amount of light available to plants affects photosynthesis by measuring the by-product of photosynthesis, oxygen.

Plants are the mediators of energy on this planet for all other living things. Through photosynthesis, plants convert sunlight energy into organic molecules, forming the basis of food for all organisms. In a series of reactions, light energy, carbon dioxide and water are combined to create food for plants.

Photosynthesis consists of two reactions, the light-dependent and light-independent reaction. The light-dependent reaction of photosynthesis involves using light energy to remove hydrogen atoms from water molecules. The light-independent reaction in photosynthesis involves changing carbon dioxide and hydrogen into organic molecules. While no light is necessary for the second part of the process to occur, light is required to initiate the photosynthetic process.

If the reactants of photosynthesis are water, light and carbon dioxide, the products are carbohydrates (stored plant energy) and oxygen gas. Plants release oxygen into the air as a byproduct of photosynthesis.

There is useful synergy between plants and animals in this reaction. The oxygen evolved by the photosynthesis reaction is a by-product the plant does not use. Humans, on the other hand, require oxygen for respiration and expel carbon dioxide.

Published: October 2003


Here's What You Need

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Probeware (PASPORT Systems)

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Xplorer GLX (PS-2002) - $389

The Xplorer GLX is a data collection, graphing, and analysis tool designed for science students and educators.

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PASPORT Oxygen Gas Sensor (PS-2126A) - $195

The Oxygen Gas Sensor accurately measures oxygen concentration in the atmosphere or in enclosed spaces.

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Other Materials

  • A large fuzzy plant leaf (such as begonia)
  • Plastic food container, with a hole cut in the side for the oxygen-sensing element of the Oxygen Gas Sensor.
  • Aluminum foil
  • Lamp or sunlight