Photosynthesis Coursework


Photosynthesis Coursework

Writing a photosynthesis coursework, you cannot avoid using a wide range of terms, concepts, and definitions.  If you have a thorough understanding of photosynthesis, it will not be a problem for you to write a good coursework.  However, if you would like professional help writing, you should try our original coursework writing help. Custom coursework is free of plagiarism and is written in accordance to your instruction from scratch by experienced writer.

Photosynthesis Coursework Sample

Recently the position of chlorophyll has been challenged. First, indications were found that the light energy absorbed by the yellow pigments also is utilized in photosynthesis. Then at the meeting of the American Association for the Advancement of Science in Chicago last December, L. R. Blinks of Stanford University presented evidence that in some red algae the light absorbed by red pigments is more effective in photosynthesis than the light absorbed by chlorophyll. If this is confirmed, the red pigments must be assumed to participate in photosynthesis directly, and not merely as handmaidens of chlorophyll. To appreciate the importance of this observation, you must remember it is estimated that 90 per cent of photosynthesis on earth is carried out, not by green land plants, but by the multicolored sea algae.

So we are beginning to get a somewhat clearer idea of the events in the light stages of photosynthesis, and recently we have also gained a little information about the dark stages. The total process, as we have noted, proceeds in two separate sequences: 1) the oxidation of water, which releases free oxygen, while hydrogen becomes attached to some intermediate "acceptor"; 2) the hydrogenation of carbon dioxide to produce carbohydrates. Each sequence of reactions apparently has a separate catalytic system. The two sequences and their relation to each other are pictured in an accompanying diagram, which shows the separate sequences as two legs, with chlorophyll as the bridge between them. One sequence (the left leg) begins with molecules of gaseous carbon dioxide. These are first bound or fixed in a form suitable for reduction, perhaps by enzymatic formation of an organic acid. The bound carbon dioxide is then reduced by hydrogen atoms supplied in light by chlorophyll, which has recovered the hydrogen from water in the other sequence. The reduction, in turn, is followed by other enzymatic transformations which lead to a carbohydrate molecule.

In the right leg we first have a similar binding of the water molecule, followed by its dehydrogenation in light, and then the enzymatic conversion of the residue into free oxygen, perhaps through the intermediate formation of a peroxide, similar to but apparently not identical with hydrogen peroxide. Some of these reactions are now being studied with the help of isotopic tracers. We are concerned with the fate of three kinds of atoms--hydrogen, carbon, oxygen. The heavy nonradioactive hydrogen, deuterium (H2), has been available since before the war; the weakly radioactive tritium (H3) is not yet generally available.

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