Chemistry for Biologists: Photosynthesis
Fate of products of the light reactions
For each electron flowing from water to NADP+ (a net change in1.14 volts), two quanta of light are absorbed, one by eachPhotosystem. Each molecule of oxygen released involves the flowof four electrons from two water molecules to two NADP+s andrequires four quanta of sunlight absorbed by each Photosystem toprovide the energy to do this. These are the "Light PhaseReactions" of photosynthesis, which produce two high energychemical products, namely NADPH and ATP.
Thus the reactions of the light-dependent stage of photosynthesis
provide a source of reducing power (NADPH) and the universal
energy-supplying molecule ATP, with oxygen gas given off as a waste
Plant Energy Transformations-Photosynthesis - …
Photosynthetic organisms use energy from sunlight to synthesize their own fuels. They can convert harvested sunlight into chemical energy (including ATP) to then drive the synthesis of carbohydrates from carbon dioxide and water. When they synthesize the carbohydrates, oxygen gets released. Globally, more than 10 billion tons of carbon is "fixed" by plants every year - this means that carbon molecules are converted from being part of a simple gas (carbon dioxide) into more complex, reduced molecules (carbohydrates), making carbon available as food for non-photosynthesizers (and of course, providing oxygen). They use some of the carbohydrate for their own growth and reproduction. It is pretty remarkable when you think about it - have you been to Sequoia National Park or seen the redwoods along our northwest coast? Massive trees, right? Think about the fact that most of that mass is in the form of carbon that was pulled out of the air as carbon dioxide!
The process of photosynthesis is two-part. First, there are the light reactions, where light is converted into chemical energy (a reduced electron carrier and ATP). This occurs in the thylakoids (stacked membranes) of the chloroplasts. The ATP and electron carriers are then used in a second set of reactions, called the light-independent reactions. This also occurs in the chloroplasts, but in an area called the stroma. In this case, carbon dioxide gets used to produce sugars in a series of reactions called the Calvin Cycle, C4 photosynthesis, and crassulacean acid metabolism. You can look in any basic bio textbook to see how much "energy" or "sugar" is produced in each step of the process.
photosynthesis | Importance, Process, & Reactions - …
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Photosynthesis - Wikipedia
no oxygen required, low levels of ATP produced; ..
chapter 4 pdf bio | Cellular Respiration | Photosynthesis
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