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Light-absorbing compounds found in photosynthetic organisms that work in tandem with chlorophyll are known as accessory pigments. They contain other forms of this pigment, such as chlorophyll b in green algal and higher plant antennae, and chlorophyll c or d in other algae. There are also many non-chlorophyll accessory pigments, such as carotenoids and phycobiliproteins that absorb light and transfer it to the photosystem chlorophyll. Some of these accessory pigments, particularly carotenoids, absorb and dissipate excess light energy or function as antioxidants. A pigment bed refers to a large, physically associated group of chlorophylls and other accessory pigments.
An absorption spectra of the various chlorophyll and non-chlorophyll pigments associated with photosystems differ, either because the spectra of different chlorophyll pigments are modified by the local protein environment or because the accessory pigments have intrinsic structural difference. As a result, in vivo, a composite absorption spectrum of all these pigments is broadened and flattened, allowing plants and algae to absorb a wider range of visible and infrared radiation. Because most photosynthetic organisms do not absorb green light well, the majority of remaining light under leaf canopies in forests or under water with abundant plankton is green, resulting in a spectral effect. Some of the cyanobacteria and red algae have accessory phycobiliproteins that absorb green light that reaches these habitats.
Accessory Pigments
Accessory pigments have a slightly different molecular structure than chlorophyll a, which allows them to absorb different colors on the light spectrum. Because chlorophyll b and c reflect different shades of green light, leaves and plants are not all the same color.
Chlorophyll obscures the less abundant accessory pigments in leaves until production ceases in the fall. The dazzling colors of accessory pigments hidden in the leaves are revealed in the absence of chlorophyll.
Types of Accessory Pigments
Chlorophyll b transmits green light and absorbs blue and red light primarily. Sun energy is transferred to chlorophyll a, a smaller but more abundant molecule in the chloroplast.
Carotenoids reflect light waves in the orange, yellow, and red spectrums. Carotenoid pigments cluster next to chlorophyll a molecules in a leaf to efficiently transfer absorbed photons. Carotenoids are fat-soluble molecules that are thought to aid in the dissipation of excess radiant energy.
Xanthophyll pigments act as antioxidants by transmitting light energy to chlorophyll a. Because of its molecular structure, xanthophyll can accept or donate electrons. The yellow colour in fall leaves is caused by xanthophyll pigments.
Anthocyanin pigment helps chlorophyll a by absorbing blue-green light. The vibrancy of apples and autumn leaves can be attributed to reddish, violet anthocyanin compounds. Anthocyanin is a water-soluble molecule that can be stored in the vacuole of a plant cell.
Antenna Pigments
Photosynthetic pigments such as chlorophyll b and carotenoids form a tightly packed antenna-like structure with protein to capture incoming photons. Antenna pigments absorb radiant energy in the same way that solar panels on a house do.
Photons are pumped into reaction centers by antenna pigments as part of the photosynthetic process. Photons excite an electron in the cell, which is then transferred to a nearby acceptor molecule and eventually used to create ATP molecules.
Function of Accessory Pigments
To comprehend their function, one must first understand the structure and function of chloroplasts, which play an important role in photosynthesis. Chlorophyll is the primary pigment that intercepts sunlight and uses it in the photosynthesis process.
They all have different absorption spectra, which means that they absorb light at different wavelengths. The chlorophyll porphyrin ring absorbs yellow and blue wavelengths while reflecting green wavelengths. They absorb light at different wavelengths (carotenoids absorb the green wavelength alongside chlorophyll b), which chlorophyll does not readily absorb.
As a result, their primary function is to transfer energy to chlorophyll a. Chlorophyll a then initiates chemical reactions in the chloroplasts, which is referred to as the light-dependent process of photosynthesis or simply Light Reactions. The product of these reactions are often used in photosynthesis Dark Reactions.
Carotenoids are the most important pigments in photosynthesis. The conjugated system occurs when the carbon bonds in the two rings of carotenoids interact with each other. This system allows electrons to move relatively freely, resulting in energy conservation. As a result, the range of light energies absorbed decreases. More light from the short end of the spectrum is absorbed, giving the pigment a red appearance.
Because of the presence of water and other organic and dissolved matter in aquatic ecosystems, the absorption spectrum of pigments varies. Because phycocyanin absorbs red wavelengths, cyanobacteria can survive in murky inland water.
Diagram of Accessory Pigments
Accessory pigments are pigments other than chlorophyll a that aid in light absorption.
They assist in the following tasks:
- Increase the wavelength range of light absorbed by the chloroplast.
- Absorb light and transfer energy to chlorophyll a, the photosynthesis reaction center.
- Avoid photo-oxidation of chlorophyll a.
Roles of accessory Pigments in Photosynthesis
The sun’s light energy initiates a chain reaction in plants, resulting in the photosynthesis of energy-rich glucose (sugar) molecules from inorganic compounds. This amazing feat is accomplished through the rearrangement of molecules in plant chloroplasts and the cytoplasm of some protests.
Chlorophyll is the primary pigment responsible for light-dependent photosynthesis. Accessory pigments such as chlorophyll b, carotenoids, xanthophyll, and anthocyanins help chlorophyll a molecule by absorbing a wider range of light waves.
Function of Photosynthesis Pigments
Photosynthesis occurs within grana, which are stacks of flat discs found in the stroma of plant cell organelles. Photons missed by chlorophyll and are captured by accessory photosynthetic pigments.
When energy levels within the cell are too high, photosynthetic pigments can also inhibit photosynthesis. During the light-dependent cycle of photosynthesis, the concentration of photosynthetic and antenna pigments in plant cells varies depending on the plant’s light requirements and access to sunlight.
Importance of Photosynthesis
The majority of food chains that comprise the food web rely on food energy produced by autotrophs via photosynthesis. Eukaryotic plant cells produce glucose in chloroplasts, which contain light-absorbing pigments such as chlorophyll a and b.
Oxygen is a byproduct of photosynthesis that is released into the surrounding water or air. Aerobic organisms such as birds, fish, animals, and humans require both food and oxygen to survive.
Conclusion
Light-absorbing compounds found in photosynthetic organisms that work in tandem with chlorophyll are known as accessory pigments. They contain other forms of this pigment, such as chlorophyll b in green algal and higher plant antennae, and chlorophyll c or d in other algae. An absorption spectra of the various chlorophyll and non-chlorophyll pigments associated with photosystems differ, either because the spectra of different chlorophyll pigments are modified by the local protein environment or because the accessory pigments have intrinsic structural difference. Accessory pigments have a slightly different molecular structure than chlorophyll a, which allows them to absorb different colors on the light spectrum. Photosynthetic pigments such as chlorophyll b and carotenoids form a tightly packed antenna-like structure with protein to capture incoming photons. To comprehend their function, one must first understand the structure and function of chloroplasts, which play an important role in photosynthesis. Chlorophyll is the primary pigment that intercepts sunlight and uses it in the photosynthesis process. The sun’s light energy initiates a chain reaction in plants, resulting in the photosynthesis of energy-rich glucose (sugar) molecules from inorganic compounds. Photosynthesis occurs within grana, which are stacks of flat discs found in the stroma of plant cell organelles. The majority of food chains that comprise the food web rely on food energy produced by autotrophs via photosynthesis.
