Chlorophylls absorption spectrum

As we indicated in Chapter 4 (Section 4.1 D), both the quantity and the quality of radiation change as a function of depth in water wavelengths near 500 nm penetrate the deepest. For instance, only about 10% of the blue and the red parts of the spectrum penetrate to a depth of 50 m in clear water, so chlorophyll is not a very useful light-harvesting pigment below that depth (see Fig. 5-3 for a chlorophyll absorption spectrum). Changes in the spectral quality (relative amounts of various wavelengths) with depth can affect the... 

Action spectra can be used to show the wavelengths of light that make photosynthesis work. If we compare this to chlorophyll absorption spectrum, we see they are a good match. This implies chlorophyll is the main pigment in photosynthesis (Fig. 13.6). 

The chlorophyll absorption spectrum shows the lack of absorption in the green wavelengths. 

FIGURE 1 The optical absorption spectrum of chlorophyll as a plot of percentage absorption against wavelength. Chlorophyll a is shown in red, chlorophyll b in blue. 

Fig. 3. Photokinetic action spectrum (circles and solid line) and in vivo absorption spectrum (long dashed line) of Phormidium ambiguum. Absorption spectrum of chlorophyll a (short dashed line). Abscissa wavelength in nm Ordinates relative response and absorbance respectively (modified after103 )...

Figure 2.2 Absorption spectrum of chlorophyll overlaid with the energy flux from the Sun...

Using the individual solvents as blanks, acquire a visible absorption spectrum of each sample. Superimpose the four spectra, and determine which solvent is the most effective solvent for extracting chlorophyll from spinach leaves. 

The sunlight is absorbed by a number of pigments, of which chlorophyll a is the most important. The absorption spectrum of chlorophyll a is shown in Fig. 10.3. Apart from chlorophyll a there are accessory pigments which function as lightharvesting antennae and transfer the energy to the chlorophyll a. This is an elegant way to efficiently collect sunlight. 

Figure 12.4 The absorption spectrum of a solution of chlorophyll a in ether...

The absorption spectrum of chlorophyll a indicates strong absorption of red and blue wavelengths. Explain why leaves appear green. 

Since chlorophyll can be removed readily from chloroplasts by mild solvent extraction, it might appear that it is simply dissolved in the lipid portion of the membranes. However, from measurements of dichroism (Gregory,226 p. Ill) it was concluded that the chlorophyll molecules within the membranes have a definite orientation with respect to the planes of the thylakoids and are probably bound to fixed structures. The absorption spectrum of chlorophyll in leaves has bands that are shifted to the red by up to 900 cm-1 from the position of chlorophyll a in acetone. Most green plants contain at least four major chlorophyll bands at 662, 670, 677, and 683 nm as well as other minor bands264 (Fig. 23-21). This fact suggested that... 

Figure 23-21 Absorption spectrum of chlorophyll in a suspension of chloroplast fragments from the green alga Scenedesmus showing the multicomponent nature of the chlorophyll environments. From French and Brown.264...

Figure 5.3 The chemical structure of a chlorophyll and its absorption spectrum...

Photosystem 1 is basically similar to the photosynthesizing system of bacteria just discussed. The difference between PSl and the photosystem of bacteria lies mainly in the fact that, instead of bacteriochlorophyll P890, the photochemical active centre of PSl contains chlorophyll a as a primary electron donor having the peak in the differential absorption spectrum at 700 nm and thus denoted as P700. In PS2 the primary donor of electrons is a chlorophyll molecule P680 with the peak in the differential optical spectrum at 680 nm. Photosystems 1 and 2 are located close to each other. Between them there is an electron transport chain containing molecules of plasto-quinones and cytochromes. 

The reduction of ring IV in chlorophylls a or b changes the optical absorption spectrum of the molecule dramatically. Whereas the long-wavelength absorption band of a cytochrome is relatively weak (see fig. 14.4), chlorophyll a has an intense absorption band at 676 nm (fig. 14.5). Chlorophyll b has a similar band at 642 nm. Bacteriochlorophylls a and b have strong absorption bands in the region of 770 nm (see fig. 15.5). The chlorophylls thus absorb red or near-infrared light very well. 

Virtually pure chlorophyll a was isolated from Cuban molasses by chromatographic and extraction procedures70 it was identified by its absorption spectrum its estimated concentration was 0.00005%. 

The absorption spectrum of Chi a has a blue band and a red band, so the characteristic color of chlorophyll is green. The band in the blue part of the spectrum has a peak at 430 nm for Chi a in ether (Fig. 5-3). This band is... 

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