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Leaming objectives :

Concepts

• Use the chemical equations for photosynthesis and cellular re summarize how each process transforms energy and matter

• Explain how autotrophs transform and store physical (solar) ener energy

• Explain how autotrophs and heterotrophs transform and access stored c emi energy for cellular use

• Identify where oxygen comes from • Predict how energy and matter will be transformed during photosynthesis and

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Pigments Chlorophyll

In autotrophs like plants, photosynthesis takes place in a cellular organelle called the chloroplast. This structure is made of a series of stacked membranes (thylakoids) that rely on concentration gradients to harness solar energy. The solar energy is absorbed by pigments like chlorophyll. You had the opportunity to examine a spectrograph of solar absorption in chloropyll last week . Not all autotrophs utilize the same pigments for solar absorption.

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Figure 1: Photosynthetically active radiation © Black Dog LEDs

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Classification of seaweeds (large marine algae) as red, green, or brown is based largely on their pigments. Because sunlight is the primary source of energy for photosynthesis, photosynthetic autotrophs that live in water must live close enough to the surface to receive at least 1 % of the incoming solar energy. The photic zone describes the layers of water Into which light can penetrate Marine scientists have observed that seaweeds are distributed in the photic zone according to their available pigments and resultant color of the available light for photosynthesis . The depth of the photic zone varies depending on conditions. In clear tropical waters , it can

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