Yellow a wavelength of 550 nm and has a bandwidth of 20–30 nm. Autumn leaves, yellow flowers, bananas, oranges and other yellow fruits all contain carotenoids, yellow and red organic pigments that are found in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria and some fungi. They serve two key roles in plants and algae: they absorb light energy for use in photosynthesis, and they protect the green chlorophyll from photodamage. In late summer, as daylight hours shorten and temperatures cool, the veins that carry fluids into and out of the leaf are gradually
Carbon fixation in the chloroplasts of plants and algae, and in the cyanobacteria. It also fixes carbon in the anoxygenic photosynthetic in one type of proteobacteria called purple bacteria, and in some non-phototrophic proteobacteria. In photosynthesis, energy from sunlight drives the carbon fixation pathway. "Oxygenic" photosynthesis is used by the primary producers—plants, algae, and cyanobacteria. They contain the pigment chlorophyll, and use the Calvin cycle to fix carbon autotrophically. The process works like this: In the first step, water is dissociated into electrons, protons, and free oxygen. This allows the use of water, one of the most abundant substances on Earth, as