Learning Objectives

• Define photosynthesis and explain its importance to life on Earth.

• Identify the reactants and products of photosynthesis (water, carbon dioxide, glucose, oxygen).

• Construct and interpret different models of photosynthesis (e.g., diagrams, chemical equations, simulations).

• Explain the transfer and transformation of energy in photosynthesis using the model.

• Analyze data from investigations related to photosynthesis (e.g., effect of different light intensities on oxygen production).

Overview of Photosynthesis

• Most autotrophs make organic compounds using photosynthesis.

• Photosynthesis is the process of converting light energy into chemical energy.

Overview of Photosynthesis

• Photosynthesis occurs in two phases.

  • In the light-dependent phase, light energy is converted into chemical energy.

  • In the light-independent phase, chemical energy used to synthesize glucose

• The absorption of light is the first step in photosynthesis.

• Once light energy is captured, it can be stored as ATP or NADPH.

  • Both are energy molecules

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Phase One: Light Reactions

​We are here

Organelles that capture light energy

• Contain two main compartments:

  • Thylakoids: flattened sac-like membranes 

    • Stacks of thylakoids are called grana.

  • The fluid filled space outside the grana called the stroma.

Chloroplasts

Phase One: Light Reactions

• Light-absorbing colored molecules called pigments are found in the thylakoid membranes.

• Different pigments absorb specific wavelengths of light.

  • Most common pigment in plants is chlorophyll.

  • Plants also have accessory pigments.

Pigments

Phase One: Light Reactions