Photosynthesis allows organisms like plants, algae and photosynthetic bacteria to turn light energy from the sun into usable chemical energy. Without this process, energy would be unable to enter our ecosystems, and we would not be able to sustain life on Earth as we know it.
Organisms that use photosynthesis rely on organelles in their cells called chloroplasts. It's within these organelles that sunlight, water and carbon dioxide can be used to create energy in the form of glucose (plus oxygen as a by-product). Within those organelles is a compound called chlorophyll. This is what gives many plants their green color and is what allows plants and algae to absorb light for photosynthesis.
However, there are different types of chlorophyll present in only certain types of organisms. This affects the color of the organism, and certain types of chlorophyll can only be found in algae.
Chlorophyll is a type of pigment. Pigments appear as a certain color since they only absorb certain wavelengths of light and reflect the light (and thus the color) that they do not absorb.
For example, the most common types of chlorophyll appear as green. This means that chlorophyll is able to absorb all light except for green wavelengths of light. The chlorophyll reflects these wavelengths, so many plants appear green.
What Is Algae?
Algae are aquatic and often unicellular organisms that use photosynthesis in order to get energy/food. Algae is actually a broad classification that can refer to a variety of organisms ranging from microscopic blue-green algae (that's actually a bacteria) to many aquatic and photosynthetic unicellular protists to seaweed and giant kelp. Algae is usually defined by the coloration, which can include green algae, brown algae, red algae and blue-green algae.
Chlorophyll A is found in all types of organisms that use photosynthesis, which includes both land plants and algae. This means that chlorophyll A is a necessary component for photosynthesis and plays a central role in the process. Specifically, chlorophyll A is responsible for absorbing light in both the red-orange and the blue-violet spectrum of light. It then is able to act as an electron donor in an electron transport chain that drives the photosynthetic reaction.
Chlorophyll A is a green pigment, which is why the majority of plants and algae and other photosynthetic organisms are green (since it's found in all organisms that photosynthesize).
Chlorophyll B is also a green pigment, and it's found in plants and green algae. Chlorophyll B absorbs blue-violet wavelength light. It isn't found in high concentrations like chlorophyll A is, which leads scientists to believe that this is more of a "helper" pigment to increase the amount of light absorbed instead of providing a necessary role to photosynthesis. This is supported by the fact that it isn't found in all photosynthetic organisms.
Chlorophyll C can be found in only certain types of algae. It's found mostly in marine algae, including diatoms, dinoflagellates and brown algae. This pigment appears as a blue-green color and is what's known as an accessory pigment. This means that it likely functions in a similar way to chlorophyll B to expand the amount of wavelengths of light that can be absorbed for photosynthesis.
Chlorophyll D is one of the rarer forms of photosynthetic pigment and is only found in species of red algae and cyanobacterium. It's thought that this chlorophyll evolved to suit algae and photosynthetic organisms that live in deep water where not much other light can penetrate.
Lastly, and most rarely, is chlorophyll E. Not much is known about this pigment except that it is found in some types of golden algae.
- Web Exibits: Causes of Color: Green Plants & Chlorophyll
- All About Algae: Algae Basics
- Missouri Botanical Garden: Algae
- Encyclopaedia Britannica: Chlorophyll
- Kimball's Biology Pages: Chlorophylls and Carotenoids
- McDaniel College: Photosynthesis Pigments
- University of California Museum of Paleontology: Photosynthetic Pigments
- Journal of the American Chemical Society: Structure, Properties and Distribution of Chlorophyll C
- Journal of Biological Chemistry: Chlorophyll D – A Green Pigment of Red Algae
- Trends in Plant Science: Chlorophyll D: The Puzzle Resolved
- Texas Parks and Wildlife: Biology of Golden Alga