Chapter 22 ("Electron Transport and Oxidative Phosphorylation") in Voet & Voet (3rd Edition) is one of the most important chapters in the entire text (at least in my opinion) and it would help to reread it as you look at the light reaction of photosynthesis in more detail over the next two lectures.
The first step in photosynthesis is the interaction of light with chlorophyll molecules. The chemical structures of the various chlorophyll molecules are based upon the cyclic tetrapyrrole that is also seen in the heme group of globins and cytochromes. Various modifications of this group, namely ring saturation characteristics and substitutions on the rings provide a series of pigment molecules that, as a group, absorb effectively over the wavelength range of 400 nm - 700 nm, the spectrum of . It is the high degree of conjugation of these molecules that makes them so efficient as absorbers of visible light.
Both the LHC and the reaction centers are membrane bound structures but there are no chloroplasts in the purple photosynthetic bacteria. The electron transfer processes occur within the cell membrane and the overall process is a cyclic one (i.e., there is no net oxidation-reduction). Protons are transferred across the membrane, from the cytoplasmic side to the outside, establishing a proton gradient whose dissipation drives ATP synthesis. A similar situation holds for the cyanobacteria and plants, but in these organisms, the process occurs in chloroplasts and the overall reaction is not a cyclic one.
The two symmetrically-related sets of molecules do not function in the same way, however. The flow of electrons is from P870 to the right-sided set, which is within the L subunit, and then over to the left-sided set, which is within the M subunit. The intervening Fe(II) atom does not directly participate in the redox reactions but it is part of the overall "circuit" that eventually ends where it started, at the special pair.
In order to take the parts of the carbohydrate, and create the chemical bonds that feed the plant, energy is needed this energy comes from photons.
Pigments: Absorbs photons while specific pigments absorb specific wavelengths.
Electron transport chains: Functions in the light reactions of photosynthesis.
Proton pumps: Transfer protons from one side of the membrane for another.
It turns out that the overall reaction of photosynthesis takes place in two steps. In the first step, the oxygen in water is oxidized by the light energy:
When one adds these two reactions together, the overall reaction (1) results. [H.], the reducing agent, is an "intermediate" in the overall reaction. It looks like two H2O molecules are needed in reaction (2) but then you get one of them back in reaction (3).
You have already studied the "dark reaction" and I will refer you to Dr. Diwan's notes on the subject. As the overall process of photosynthesis involves a series of electron transfer reactions, we are in the realm of oxidation-reduction chemistry, and it would help to review the basics of these processes because we will be going into this topic in greater depth. There is a direct analogy to electron transfer in the mitochondrion, in which clumps of energy are transferred from one electron carrier to another along a "chain" and H+ ions are translocated out, across the mitochondrial membrane, thus generating an electrochemical gradient. The energy inherent in this gradient is used to synthesize ATP in the process of "oxidative phosphorylation." The same processes occur in photosynthesis and the chloroplast, the site of photosynthesis in plants and blue-green algae (but not in photosynthetic bacteria), is the analog of the mitochondrion in eukaryotes.
Notice that the oxidation state of the carbon atom has changed from +4 to 0, and so an overall reduction reaction has occurred. Here, "(CH2O)" represents a carbohydrate. You'll also notice that there's been a change in the oxidation state of oxygen, since its oxidation state is almost always "-2" when combined with other atoms, but it is "0" in its natural state of O2. So, oxygen (water) is oxidized in the overall process.
Definition : Photosynthesis is the intracellular anabolic process, characteristic of the green cells of plants in which carbohydrates are synthesized from carbon dioxide and water in the presence of light and chlorophyll. In this process, light energy is converted into chemical energy and stored in carbohydrate molecules, while oxygen is liberated.
Aug 22, 2017. photosynthesis Photosynthesis, process by which green plants and certain other organisms transform light energy into chemical energy. Britannica Kids. Photosynthesis, the process by which green plants and certain other. The overall chemical reaction for photosynthesis is 6 molecules of carbon dioxide CO2 and 6 molecules of water H2O, with the addition of solar energy. You need to remember that the overall metabolism of an organism includes thousands of chemical reactions. The reactions in glycolysis and photosynthesis are.
Feb 6, 2017. Find out what the products of photosynthesis are and view the overall chemical reaction and equation. In the Light-Independent Process the Dark reaction. comes from the first phase of the photosynthetic process. This lesson will go over the basics of photosynthesis and its chemical reaction, explaining how the chemical equation is formed and how it can be.