The third key characteristic used to distinguish algae is the product they store for energy. Many store different sugars, like the green algae which store starch and specialized derivatives, and the blue-greens that store glycogen, while others have moved away from storing sugars entirely. The most notable example of this are the Bacillariales, which are unique in their storage of lipids. Often, the lipids are visible as oil droplets in the cytoplasm, ranging in size from small to very large and distinct.
Like higher plants, algae use photosynthesis to generate energy from sunlight and carbon dioxide. In green algae like closterium, photosynthesis occurs in the chloroplast which is easily visible as a large green band in each semi-cell. Here the algae produces starch which is then stored for energy. Additionally, each chloroplast contains pyrenoids, visible as the dark green circles. These little compartments work to fix carbon dioxide in the cell which increases the overall efficiency of the photosynthetic machinery in the cell.
Emily Tellschow
Undergradute Senior
Ecology and Evolutionary Biology major
Chemistry minor