What is Photosynthesis: Definition and 66 Discussions

Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's metabolic activities. This chemical energy is stored in carbohydrate molecules, such as sugars and starches, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek phōs (φῶς), "light", and sunthesis (σύνθεσις), "putting together". In most cases, oxygen is also released as a waste product. Most plants, algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies most of the energy necessary for life on Earth.Although photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centers that contain green chlorophyll pigments. In plants, these proteins are held inside organelles called chloroplasts, which are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane. In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, producing oxygen gas. The hydrogen freed by the splitting of water is used in the creation of two further compounds that serve as short-term stores of energy, enabling its transfer to drive other reactions: these compounds are reduced nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine triphosphate (ATP), the "energy currency" of cells.
In plants, algae and cyanobacteria, long-term energy storage in the form of sugars is produced by a subsequent sequence of light-independent reactions called the Calvin cycle. In the Calvin cycle, atmospheric carbon dioxide is incorporated into already existing organic carbon compounds, such as ribulose bisphosphate (RuBP). Using the ATP and NADPH produced by the light-dependent reactions, the resulting compounds are then reduced and removed to form further carbohydrates, such as glucose. In other bacteria, different mechanisms such as the reverse Krebs cycle are used to achieve the same end.
The first photosynthetic organisms probably evolved early in the evolutionary history of life and most likely used reducing agents such as hydrogen or hydrogen sulfide, rather than water, as sources of electrons. Cyanobacteria appeared later; the excess oxygen they produced contributed directly to the oxygenation of the Earth, which rendered the evolution of complex life possible. Today, the average rate of energy capture by photosynthesis globally is approximately 130 terawatts, which is about eight times the current power consumption of human civilization. Photosynthetic organisms also convert around 100–115 billion tons (91–104 petagrams) of carbon into biomass per year. The phenomenon that plants receive some energy from light – in addition to air, soil, and water – was first discovered in 1779 by Jan Ingenhousz.

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  1. louis_slicka

    Why is green light not useful for photosynthesis?

    Plant leaves only appear green because they absorb the red and blue wavelengths of light and reflect green away. Is there an intrinsic and innate reason for this that relates to the physics of light? Maybe green wavelengths are inefficient at storing energy in chemical bonds? Have plants simply...
  2. karush

    MHB S8. 3.7.10 at which photosynthesis takes place (min/max)

    10. The rate (in mg carbon$/m^3/h$) at which photosynthesis takes place for a species of phytoplankton is modeled by the function $P=\dfrac{100I}{I^2 + I + 4} $ where I is the light intensity (measured in thousands of foot-candles). For what light intensity is $P$ a maximum? OK I presume...
  3. A

    A Quantum biology - photosynthesis

    I am having trouble understanding this paper if anyone could explain it in a better way, I'd appreciate it. https://www.nature.com/articles/nature05678
  4. V

    Chemistry Looking for Good Books on Photosynthesis

    Hello, I am interested in learning more about photosynthesis. My background is in physics, mostly condensed matter and atomic physics (graduate level). I have not taken a chemistry course since high school but I am looking for a book that starts from a physics point of view anyway. What are some...
  5. qnach

    When did people start to call it an "antenna"

    The photosynthesis light harvesters are called antenna. But when did people started to call it antenna? The earliest I can find is about 1970. I believe it should be even earlier.
  6. bbbl67

    Why does photosynthesis produce O2 from CO2?

    My understanding is that the CO2 to O2 reaction is endothermic, so it takes more energy to be put in than you get back. So if plant life is attempting to get energy from photosynthesis, then why would it do an endothermic reaction which would take energy away from its cells?
  7. K

    CAM photosynthesis saturation / trying to parse a paper

    Hi - I'm working to accumulate data on photosynthetic flux saturation levels across a range of plant species, and am having a bit of trouble understanding this paper: https://onlinelibrary.wiley.com/doi/epdf/10.3732/ajb.94.8.1344 Table 5 shows PPFD vs. ETR, and shows photosynthesis saturating...
  8. Isaac0427

    How is water produced in photosynthesis?

    I have looked everywhere, but most of the sources say water is not produced (which is not true), and some sources, such as my biology textbook, simply say it is produced. I know for every 6CO2 put into the Calvin cycle, 6 oxygen atoms are put into 2*G3P. Where do the other 6 leave the Calvin...
  9. A

    I Photosynthesis and quantum randomness

    Some studies suggest that during photosynthesis, electrons travel all possible paths simultaneously, and then always collapse at the reaction center. My question is, doesn't that contradict quantum randomness? Shouldn't the location of the electron after the collapse be predictably random?
  10. EnumaElish

    Have we solved quantum photosynthesis?

    Does this mean we've solved the quantum trick in photosynthesis? Cf. http://m.phys.org/news/2014-01-quantum-mechanics-efficiency-photosynthesis.html Or is that delegated to the "microbes" in there?
  11. Aafia

    Medical How did scientists observe metabolic pathways in organisms?

    how the scientists observed that macromolecules like proteins, carbohydrates and lipids are synthesized from other molecules with intermediate products by living cells. Did they observe this under microscope. I want to know this because I am studying bioenergetics and while studying...
  12. N

    What is the Size of a Chlorophyll Molecule and Photosystem in Biology?

    can any biology expert tell me the size of a chlorophyll molecule and the size of a photosystem ?
  13. skepticwulf

    Do plants need direct sunlight?

    We all know the famous theory that an asteroid hits the Earth and kill the dinosaurs by starting a chain reaction where the dust is all over the atmosphere preventing sunlight to reach plants causing them eventually to die thus causing herbivorous to die thus causing carnivorous to die. But when...
  14. Kior

    Timescale of the biological pump?

    I'm tying to find any clue about the timescale of the biological pump. That the carbon is recycled to the surface ca. 1,000 years is clear but the timescale of the biological pump seems hard to find. There is an report I saw when I was surfing the internet saying that the timescale can range...
  15. B

    Unlocking the Potential of Titan: Igniting Methane Oceans for Photosynthesis

    If a methane-filled planet or moon like Titan was pulled toward a star, as the methane warmed and became gaseous, would it be possible to ignite it, converting the methane oceans to H2O with a CO2 atmosphere, which could in turn cause photosynthesis to naturally occur? If it's possible, it...
  16. Suraj M

    ATP Requirements for C3 & CAM Photosynthesis

    i was told that the ATP required to form 1/6 Glucose from 1 CO₂ in C4 cycle is just 3 but 5 in CAM plants... dont both need 5 CO₂ and also why 5 CO₂?? 3 for C3 cycle ..fine one for regeneration of pyuruvic acid to PEP..fine what about the other 1 ?
  17. gfd43tg

    Why Aren't Leaves Sweet Despite Containing Sugar from Photosynthesis?

    So I was thinking, in the process of photosynthesis ##CO_{2} + 6H_{2}O \xrightarrow{light} C_{6}H_{12}O_{6} + 6O_{2}## Where is the glucose being deposited in the leaf tissue? Also, why aren't leaves sweet if I were to eat them, considering they are making sugar!
  18. W

    Dissertation guidance -- Non-linear Diff. Eqs and Photosynthesis

    Hi everyone. I am doing research about what happens to light energy after it has been absorbed by a leaf but before it has been used in the photosysnthetic reactions. For that I need to use system of 3 nonlinear ordinary differential equations. My dissertation title is : A hybrid numerical...
  19. O

    Can Glucose Synthesis be Achieved Technically?

    Can this photo synthesis be done by technical means or is it only happen in plants? Synthesis: 6CO2 + 6H2O(gas) + sun radiation = C6 H12 O6(Glucose) + 6O2 Revers: (cellular respiration) C6 H12 O6(Glucose) + 6O2 = 6CO2 + 6H2O(gas) + caloric energy (deltaG) deltaG = -2880 kJ per mole...
  20. M

    Why is quantum physics needed to explain photosynthesis ?

    Why is quantum physics needed to explain photosynthesis? In what aspect does the corresponding classical theories for photosynthesis fail?
  21. C

    Convertion of energy through photosynthesis

    Homework Statement Plants take __radiant___ energy and convert it into __chemical___energy via photosynthesis.??
  22. I

    A few questions concerning photosynthesis experiments

    For the iodine test, How does boiling alcohol speed up the diffusion of chlorophyll out of the cells? Why does the leaf become crisp and breaks easily after it has been dehydrated by alcohol? For the detection of oxygen produced from photosynthesis, Why does sodium hydrogencarbonate...
  23. Q

    Low Wavelength and Photosynthesis

    I realize this is not a biology forum. Check out the attachment. As expected, plants can use some low wavelength ultraviolet light for photosynthesis. However, the photosynthetic process seems to go nuts when x-rays are used. This is the first time I've ever heard of this. Even gamma rays...
  24. C

    Global temperature anomaly and photosynthesis.

    Hi I was just wondering if the Global Temperature anomaly fluctuates up and down rapidly be cause of photosynthesis. http://www.skepticalscience.com/images/co2_temp_broad.gif see image above. as you can see the red line fluctuates rapidly...is this photosynthesis, or is it because the...
  25. N

    Quantum Phenomena of Photosynthesis

    Can someone confirm this as true or as crank-science. I tried looking for any publication of this but haven't found anything. "They were trying to establish exactly how organic photosynthesis approaches 95% efficiency, whereas the most sophisticated human solar cells operate at only half...
  26. P

    Is Quantum Entanglement the Secret Behind Photosynthesis?

    http://www.physorg.com/news192726440.html researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC), Berkeley have recorded the first observation and characterization of a critical physical phenomenon...
  27. J

    Photosynthesis converts CO2 into sugars, can we industrialize this process?

    CO2 appears to create global warming, but is there a way to get rid of the CO2? Could we somehow industrialize the photosynthesis process to get rid of large amounts of CO2? What sorts of issues prevent this solution?
  28. H

    Respiration decrease during photosynthesis?

    I guess respiration is lower during photosynthesis, or you would get max vegetation growth with 24/0 light, dark rate. For how long can the "supply" created by photosynthesis supply respiration? What is the best light/dark relationship for eg. Weeds. Photorespiration Photorespiration is...
  29. D

    Was Photosynthesis at first sustainable?

    Hi I was thinking about photosynthesis recently and I know that it first evolved in cyanobacteria like organisms to convert sunlight into chemical energy. It also produced oxygen from water (not CO2) to oxidize the atmosphere. I read that many Eukaryotic organisms need oxygen in order to live...
  30. M

    Non-Cyclic Phosphorylation of Photosynthesis

    Homework Statement Dear All, I would like to ask you a question as the concept doesn't seem to be best explained on my book. It is stated that during non-cyclic phosphorylation two electrons (One per molecule of Chlorophyll in the reaction center.) leave PSI, travel an electron transport...
  31. N

    Earth Mass Increasing? Photons and Photosynthesis making more matter on earth?

    This is a question for whoever is out there. Is the Earth's mass ever increasing? I understand that under the Second Law of Thermodynamics, the Earth is a closed system, ie it exchanges energy with its environment, but not matter. So, my question is, if sunlight energy is constantly...
  32. G

    What Wavelengths of Light are Most Effective for Photosynthesis?

    What wavelengths of light can plants grow in? Which do they grow best in? How much does this differ from plant to plant? For example, could you grow a plant under monochromatic light? Infrared light? UV light?
  33. GRB 080319B

    Photosynthesis Chlorophyll wavelength absorption

    Why do the chlorophyll in land plants absorb primarily in the blue and red wavelengths, http://en.wikipedia.org/wiki/File:Solar_Spectrum.png" ? Isn't more energy available in 500nm green light vs 700nm red light? E =\frac{hc}{\lambda}
  34. L

    Can ultrafast lasers help us understand the complex process of photosynthesis?

    Warning: This is a potentially stupid question! Is it possible to induce photosynthesis with laser light? What kind of published work is there on it? Thanks!
  35. O

    Quantum effects Photosynthesis

    I would like to hear some thoughts about the quantum effects that seem to be an important part of the photosynthesis (http://www.lbl.gov/Science-Articles/Archive/PBD-quantum-secrets.html" ). According to the scientists who made this discovery it seems that the photon tests all possible paths...
  36. Loren Booda

    Photosynthesis vs. carbonization

    The major man-made sources of carbon dioxide are combusted wood, petroleum, coal and natural gas (all of which, in turn, originated from plant life). Can we counter this process of generating CO2 by capturing it with an enhanced global photosynthesis?
  37. T

    *Can it be?* Economical artificial photosynthesis at MIT

    According to the following documentation: http://web.mit.edu/newsoffice/2008/chem-solar-0620.html" MIT chemists Nocera, Peters and Christopher Cummins have developed a device that uses sunlight to split water into hydrogen and oxygen gases. "When sunlight strikes the artificial photosynthesis...
  38. T

    Can Artificial Photosynthesis be a Fossil Fuel Alternative?

    If we can achieve artificial photosynthesis, might it replace fossil fuels once and for all? Can it also be an effective engine in vehicles?
  39. W

    What Happens to Hydrogen in Photosynthesis?

    Homework Statement Okay, i know basically how photosynthesis occurs, and i know the equation. but i don't understand how the hydrogen comes in. where does it go after it 'gives' its electrons away? Homework Equations oh, just fyi here is the equation...
  40. T

    How much is the energy efficiency of the process of photosynthesis?

    Homework Statement During photosynthesis found that a plant is necessary to absorb 8 photons of red light with wavelength 6850 Å to produce an O2 molecule. The average energy storage during photosynthesis is 112 kcal per mole O2. Calculate the energy efficiency of the process of...
  41. M

    How Does Introducing a Competitive Inhibitor of Rubisco Affect Photosynthesis?

    Homework Statement Suppose that a competitive inhibitor of rubisco is introduced into chloroplasts. Which of the following statements is a logical consequence: (a) The light reactions will slow down, since electron carriers will be scarce. (b) The light reactions will speed up to drive the...
  42. I

    Multipage Posters on Cellular Respiration, Photosynthesis (Calvin Cycle) etc

    Since I'm such a geeky person (trust me, my computer desktop background are digits of the pi), I'm looking for multipage posters (several A4 sheets of paper) in which I can just print out, tape them, and stick them on my wall. As said in the thread title I am looking for posters for the...
  43. D

    Photosynthesis - process and variables

    Homework Statement I was wondering if there was anybody in here with an understanding of the photosynthesis process? If so, would you be willing to read my description of it and ensure that all information is valid and accurate. Thanks
  44. E

    Biology Lab Abstract: Photosynthesis

    [SOLVED] Biology Lab Abstract: Photosynthesis Homework Statement I am having trouble understanding how increased transmission is an indication to photosynthesis occurring. My teacher gave us the prediction for this lab: if photosynthesis is happening then transmittance goes up. I know...
  45. A

    Photosynthesis: Impact of Color on Rate & CO2 Levels Explained

    In which color will the rate of photosynthesis be greatest, smallest and how will this be reflected in the CO2 levels, why?
  46. X

    Understand Changes in Photosynthesis Graph

    http://img80.imageshack.us/img80/1017/26119684vg0.jpg This graph shows changes that occur in the amounts of ribulose 1,5 - bisphosphate (RuBP) and phosphoglyceric acid (PGA) in leaf mesophyll cells during a six minute interval of sunlight with the concentration of carbon dioxide being...
  47. C

    The Significance of Photosynthesis and Respiration in Plants and Animals

    why is photosynthesis and respiration is important in plants and animals
  48. I

    Cool research: quantum secrets of photosynthesis

    For a press release about a cool looking paper: http://www.netscape.com/viewstory/2007/04/12/quantum-secrets-of-photosynthesis-revealed/?url=http%3A%2F%2Fwww.lbl.gov%2FScience-Articles%2FArchive%2FPBD-quantum-secrets.html&frame=true
  49. X

    Coursework help: the affect on a plant on the rate of photosynthesis

    ey! i reli need sum help wit ma biology coursework "the affect on a plant on the rate of photosynthesis" kan ne1 help me owt pleeeeeeeeeeeez
  50. P

    Photosynthesis occurs in all plant life and makes plant green

    Photosynthesis occurs in all plant life and is responsible for making them green. Why are not all plant life green. I.e. flowers can be yellow, red and some leaves too like the leaves of Poinsettia. Is the reason because no photosynthesis goes on in them? Or is something else more dominant...