A light-harvesting complex is one or more polypeptide chains containing photosynthetic pigments, which surrounds a photosynthetic reaction centre and focuses light inward toward its core. Many such proteins have an alpha solenoid tertiary structure. Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. ... The leaf is the primary site of photosynthesis in plants. ... For animal and plant pigments, see Pigment, biology. ... A photosynthetic reaction centre is a protein complex which is the site of photosynthetic reactions. ... A trimer of the peridinin-chlorophyll-containing protein from the dinoflagellate Amphidinium carterae illustrating the alpha solenoid fold. ... In biochemistry, the tertiary structure of a protein is its overall shape. ...

Light harvesting complexes in plants

Chlorophyll b and carotenoids are important in light harvesting complexes present in plants. Chlorophyll b is almost identical to chlorophyll a except it has a formyl group in place of a methyl group. This small difference makes chlorophyll b absorb light with wavelengths between 400 and 500 nm more efficiently. Carotenoids are long linear organic molecules which have alternating single and double bonds along their length. Such molecules are called polyenes. 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. Chlorophyll is a green photosynthetic pigment found in plants, algae, and cyanobacteria. ... Carotenoids are organic pigments naturally occurring in plants and some other photosynthetic organisms like algae, some types of fungus and some bacteria. ... In chemistry a methyl-group is a hydrophobic Alkyl functional group which is derived from methane (CH4). ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength [citation needed]. The elementary particle that defines light is the photon. ... The wavelength is the distance between repeating units of a wave pattern. ... Organic chemistry is a specific discipline within the subject of chemistry. ... Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... Carotene is responsible for the orange colour of the carrots and many other fruits and vegetables. ... Popular Japanese fashion magazine throughout the 1990s; the photography of which has recently been reissued in two collections from Phaidon press. ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms ( flowering plants; Division Magnoliophyta). ...

The carotenoid molecules also serve a safeguarding function. Carotenoid molecules suppress damaging photochemical reactions, particularly those including oxygen, which exposure to sunlight can cause. Plants that lack carotenoid molecules quickly die upon exposure to oxygen and light. General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ...

The chlorophyll b and carotenoids present in the light harvesting complexes are referred to as accessory pigments. These accessory pigments are held inside the light harvesting proteins in a highly uniform fashion. The light harvesting complexes are cylindrical in form and come in two sizes: LH-1 which are large and completely surround the reaction centre and LH-2 which are smaller and are arranged in a ring structure around the LH-1 complex. The relative size and positioning of the proteins is shown in the image above. LH-2 is the most abundant membrane protein in plant chloroplasts. Each protein contains 7 chlorophyll a molecules, 6 chlorophyll b molecules and 2 carotenoid molecules. An electron micrograph of a series of reaction centres and light harvesting complexes from the surface of the thylakoid membrane inside a chloroplast. ...

Phycobilisome

The layout of protein subunits in a phycobilisome.

Little blue or red light reaches algae which reside at a depth of 1 metre or more in seawater, as this light is absorbed by seawater and fluorescent pigments of photosynthetic organisms above. A phycobilisome is a light-harvesting protein complex present in cyanobacteria, glaucocystophyta, and red algae. Fluorescent pigments, which are linked to the peptide chain absorb green light or red light. Other pigments which are present in the bacterial photosynthetic reaction centers, like bacteriochlorophyll and bacteriopheophytin do not absorb light in these regions. The fluorescent pigments which are present in the phycobilisome, such as phycocyanobilin and phycoerythrobilin re-emit the green light in regions which the other photosynthetic pigments can absorb. Orders The taxonomy of the Cyanobacteria is currently under revision. ... The glaucophytes are a tiny group of freshwater algae. ... Possible classes Florideophyceae Bangiophyceae Cyanidiophyceae The red algae (Rhodophyta, pronounced /ˈrəʊdə(ʊ)ˌfʌɪtə/, ancient greek: rhodos phytos = red plant) are a large group of mostly multicellular, marine algae, including many notable seaweeds. ...

The geometrical arrangement of a phycobilisome is very elegant and results in 95% effiency of energy transfer. There is a central core of allophycocyanin which sits above the photosynthetic reaction center. There are phycocyanin and phycoerythrin subunits which radiate out from this center like thin tubes. This increases the surface area of the absorbing section and helps focus and concentrate light energy down into the reaction center. The energy transfer from exited electrons absorbed by pigments in the phycoercythrin subunits at the periphery of these antennas appears at the reaction centre in less than 100 ps.