klóróplastar

Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. They are the sites where light energy is converted into chemical energy through the process of photosynthesis. Chloroplasts contain chlorophyll, a green pigment that absorbs sunlight.

The structure of a chloroplast is complex. It is enclosed by a double membrane, the outer and inner envelope. Within the inner membrane is the stroma, a fluid-filled space that contains enzymes, ribosomes, and chloroplast DNA. Suspended within the stroma are thylakoids, flattened sacs that are often arranged in stacks called grana. The thylakoid membranes contain chlorophyll and other pigments involved in light absorption. The light-dependent reactions of photosynthesis occur in the thylakoid membranes, while the light-independent reactions (Calvin cycle) take place in the stroma.

Chloroplasts are essential for life on Earth as they produce most of the oxygen in the atmosphere and provide the energy source for most ecosystems through photosynthesis. They are believed to have originated from cyanobacteria through endosymbiosis, a process where one organism lives inside another. This theory is supported by the presence of their own DNA and ribosomes within chloroplasts, which are similar to those found in bacteria.