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The cyclic light-dependent reactions occur only when the sole photosystem being used is photosystem I. Photosystem I excites electrons which then cycle from the transport protein, ferredoxin (Fd), to the cytochrome complex, b 6 f, to another transport protein, plastocyanin (Pc), and back to photosystem I. A proton gradient is created across the ...
Photochemical action plots are a scientific tool used to understand the effects of different wavelengths of light on photochemical reactions.The methodology involves exposing a reaction solution to the same number of photons at varying monochromatic wavelengths, monitoring the conversion or reaction yield of starting materials and/or reaction products.
In biology, phototropism is the growth of an organism in response to a light stimulus. Phototropism is most often observed in plants , but can also occur in other organisms such as fungi . The cells on the plant that are farthest from the light contain a hormone called auxin that reacts when phototropism occurs.
For example, in green plants, the action spectrum resembles the absorption spectrum for chlorophylls and carotenoids with absorption peaks in violet-blue and red light. In red algae, the action spectrum is blue-green light, which allows these algae to use the blue end of the spectrum to grow in the deeper waters that filter out the longer ...
The forward reaction with light is not dependent on temperature, though low temperatures give increased stability of the covalent linkage, leading to a slower reversal reaction. [ 13 ] Light excitation will lead to a conformational change within the protein, which allows for kinase activity. [ 14 ]
Phytochrome is the only known photoreceptor that absorbs light in the red/far red spectrum of light (600-750 nm) specifically and only for photosensory purposes. [1] Phytochromes are proteins with a light absorbing pigment attached called a chromophore. The chromophore is a linear tetrapyrrole called phytochromobilin. [7]
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The action spectra of chlorophyll molecules are slightly modified in vivo depending on specific pigment-protein interactions. An action spectrum is a graph of the rate of biological effectiveness plotted against wavelength of light. [1] It is related to absorption spectrum in many systems.