Cyanobacteria are photosynthesizing prokaryotes and are components of plankton i
ID: 189938 • Letter: C
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Cyanobacteria are photosynthesizing prokaryotes and are components of plankton in marine communities. Plankton form the base of the marine food web, so their diversity and abundance is critical to the survival of that ecosystem appears blue green appears red reflects blue- green light absorbs orange- red light reflects red light absorbs green- yellow light BS4 appears blue-green and BS5 appears red An organism's color depends on the wavelengths of light that the organism reflects, not on the wavelengths of light that it absorbs What wavelength of light does each use (i.e absorb) to drive photosynthesis? What wavelength of light could you shine on cyanobacteria to get them to grow the fastest? Would visible light, UV light, or infra-red light be most effective? Perhaps they require a combination of different wavelengths? BS4 contains PC BS5 contains PE Figure 1 Absorption and reflection of different pigments from cyanobacteria BS4 and BS5 These cyanobacteria are able to absorb light because they contain specific light-absorbing pigments. BS4 appears blue-green because it contains the pigment phycocyanin (PC) which absorbs orange-red light for energy, and reflects blue-green light that gives it the color you see BS5 appears red because it contains the pigment phycoerythrin (PE), which absorbs green-yellow light and reflects red light (Figure 1) Scientists hypothesized that BS4 and BS5 are able to coexist in the same marine environment because they utilize different parts of the visible light spectrum. To test this in an experiment, they used a third cyanobacterium, Tolypothrix tenuis. This species is capable of "chromatic adaptation," it can adjust the levels of PC and PE to take advantage of available wavelengths of light. In the presence of BS4, Tolypothrix produced PE in greater quantities and appeared red s this what you would have expected? What do you think happened when the same experiment was conducted with a mixture of Tolypothrix with BS5?Explanation / Answer
These pigments form the part of photosystems which use the photonic energy to break bonds and generate electrons, which passed on to a series of other molecules and is used eventually in glucose synthesis. A particular pigment is excited by a particular range of wavelengths.
In the experiment, Tolypthrix produced PE in greater quantities as BS4 has PC which absorbs orange-red, leaving behind blue-green to be absorbed only by PE. So yes this is what we must have expected. If Tolypthirx was cultivated with BS5, it will synthesize more of PC as BS5 has PE which absorbs BLUE-GREEN, leaving behind orange-red to be absorbed only by PC
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