Cyanobacteria had a role in the evolution of eukaryotic cell, more precisely their organelles. It has been shown that chloroplast, cell organelles found in some eukaryotic lineages, which are specialized in performing the photosynthesis evolved from cyanobacteria through the process called endosymbiosis. In this process, photosynthesizing cyanobacteria was engulfed in some ancient eukaryotic cell. Eukaryotic cells have evolved from the endosymbiotic events. <span>By producing and releasing O2 (as a byproduct of photosynthesis), cyanobacteria are thought to have converted the early oxygen-poor, reducing atmosphere into an oxidizing one. This caused the Great Oxygenation Event which dramatically changed the Earth's life forms and led to the formation of multicellular organisms.</span>
Carbohydrates can be found in bean and dairy products they are important for the body because they are nutritents that provide energy nucleic acids are polymeric macromolecules that are essential
From the description you make, it's likely that the structure with letter A is the chloroplast. It is round and small and it's free because of the pigment needed for photosynthesis (chlorophyll). It is located inside the cell, suspended in the cytoplasm.
