viherhiukkasten

Viherhiukkaset, often translated as green particles or chloroplasts in English, are the organelles within plant cells and eukaryotic algae that conduct photosynthesis. These are specialized structures responsible for converting light energy into chemical energy in the form of glucose. The characteristic green color of plants is due to the pigment chlorophyll, which is housed within the viherhiukkaset. Chlorophyll plays a crucial role in absorbing sunlight, primarily in the red and blue wavelengths, while reflecting green light.

Viherhiukkaset contain internal structures called thylakoids, which are flattened sacs arranged in stacks known as grana. It is within the thylakoid membranes that the light-dependent reactions of photosynthesis occur. The fluid-filled space surrounding the grana is called the stroma, where the light-independent reactions, also known as the Calvin cycle, take place. This process utilizes the energy captured during the light-dependent reactions to fix carbon dioxide from the atmosphere into sugars.

These organelles have their own DNA, separate from the nuclear DNA of the cell, and replicate independently. This characteristic has led to the endosymbiotic theory, which proposes that viherhiukkaset originated from free-living photosynthetic bacteria that were engulfed by an ancestral eukaryotic cell. The presence and function of viherhiukkaset are fundamental to most ecosystems on Earth, as they form the base of the food chain by producing organic matter and releasing oxygen as a byproduct of photosynthesis.