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Carotenoids are produced by all photosynthetic organisms and are primarily used as accessory pigments to chlorophyll in the light-harvesting part of photosynthesis. They are highly unsaturated with conjugated double bonds , which enables carotenoids to absorb light of various wavelengths .
In plants, carotenoids can occur in roots, stems, leaves, flowers, and fruits. Carotenoids have two important functions in plants. First, they can contribute to photosynthesis. They do this by transferring some of the light energy they absorb to chlorophylls, which then uses this energy for photosynthesis. Second, they can protect plants which ...
Carotenes contribute to photosynthesis by transmitting the light energy they absorb to chlorophyll. They also protect plant tissues by helping to absorb the energy from singlet oxygen, an excited form of the oxygen molecule O 2 which is formed during photosynthesis.
In addition, there are many non-chlorophyll accessory pigments, such as carotenoids or phycobiliproteins, which also absorb light and transfer that light energy to photosystem chlorophyll. Some of these accessory pigments, in particular the carotenoids, also serve to absorb and dissipate excess light energy, or work as antioxidants. [1]
The carotenoids have another role as an antioxidant to prevent photo-oxidative damage of chlorophyll molecules. Each antenna complex has between 250 and 400 pigment molecules and the energy they absorb is shuttled by resonance energy transfer to a specialized chlorophyll-protein complex known as the reaction center of each photosystem . [ 1 ]
Two examples of carotenoids are lycopene and β-carotene. These molecules also absorb light most efficiently in the 400 – 500 nm range. Due to their absorption region, carotenoids appear red and yellow and provide most of the red and yellow colours present in fruits and flowers. The carotenoid molecules also serve a safeguarding function.
Carotenoids with preferential affinity to different organs may serve as a vector for the whole particles and for more targeted delivery of their “cargo” of bioactive molecules. Inclusion of carotenoids into complexes with hydrophobic bioactive molecules, which have metabolic or therapeutic targets in particular organs, can reduce their ...
Within plants, carotenoids play the major roles of allowing light to be absorbed via photosynthesis as well ad providing photoprotection through a non-photochemical quenching. [2] The tetraterpene is also a product of the degradation of carotene and thus represents an important biomarker. However, where carotene has double bonds, carotane only ...