by Megan Worley

Created on: December 05, 2008

Algae are plant organisms that contain chlorophyll and use that and other pigments to capture the energy from sunlight and convert it into food molecules. The process through which that is complete is called photosynthesis. Algae generally store those food molecules in a form of carbohydrates. There are an astounding 30,000 species of algae, including the enormously complex seaweeds that populate our oceans. Algae are found in nearly all large bodies of water and even on some damp areas of land.

Chlorophyll is usually the primary pigment used to process energy in most plants. In algae however that are a wide variety of accessory pigments that can also be used. This is the reason that algae can come in such a wide range of colors. Aside from green algae can come in a blue-green color or red or brown. These pigments are stored in chloroplasts just like in other plants.

Algae are the most important photosynthesizing organism that lives on Earth. They can capture more of the sun's energy and can produce more oxygen than nearly all other plants combined. This has huge implications because humans depend both on the glucose that plants store as energy and on the oxygen these organisms release as a by-product. Algae are also very important in removing carbon dioxide from the atmosphere.

Photosynthesis occurs within a cell structure called a chloroplast, which is an oval-shaped structure divided into several disk shaped compartments. The compartments are called thylakoids and are arranged vertically in the chloroplasts. Within each thylakoids are hundreds of chlorophyll molecules which are responsible for trapping light molecules. Photosynthesis occurs in two stages, the light reactions and the dark reactions. During the light reaction the light energy excites to pigments in the organism to a high energy level, which is then used to make ATP and NADPH. These two compounds are then consumed during the dark reaction and turned into carbohydrates.

Photosynthesis is affected by three main principles which include light irradiance and wavelength, the concentration of carbon dioxide and the temperature. Algae have had to adapt their process of photosynthesis to overcome these barriers. In order to do so, and because many algae live in different areas, they have developed different pigments. These pigments absorb different wavelengths of light. Leaves that turn red in the fall do so to absorb a different wavelength of light, algae that is a red or brown color can absorb that same wavelength.

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