Photosynthesis: History, Processes, and Light Reactions - PDF

MODULE 4: PHOTOSYNTHESIS History of Photosynthesis *Plants are soil eaters -​ Aristotle believed that plants consumed soil for growth. But Disproven by advancements in scientific methods *Plant matter comes from water alone (Jan Baptitste van Helmont) -​ The Willow tree experiment...

MODULE 4: PHOTOSYNTHESIS History of Photosynthesis *Plants are soil eaters -​ Aristotle believed that plants consumed soil for growth. But Disproven by advancements in scientific methods *Plant matter comes from water alone (Jan Baptitste van Helmont) -​ The Willow tree experiment was partially correct, but it laid the groundwork for understanding plant nutrition *Vegetation requires injured air plants produce O2 = dephlogisticated air (Joseph Priestley) -​ The critical step in linking plant activity to atmospheric oxygen *Photosynthesis depends on CO2 = fixed air (Jean Senebler) -​ His work provided the clear connections between plants and carbon dioxide (fixed air) -​ Swiss botanist *Two gases involved in photosynthesis = 02 AND CO2 (Lavosier, etc) -​ Father of Modern Chemistry *Water is an important requirement (Nicholas de Saussure) -​ His work expanded on earlier studies and established that plants absorbed water and carbon dioxide, demonstrating the integration of these two components in the production of organic matter. -​ *CO2 +H2O +LIGHT = organic matter + o2 -​ Represents the core of photosynthesis *Red and blue light is effective in producing O2 during photosynthesis (Engelman) -​ Experimented with filamentous algae and prism. This finding laid the groundwork for understanding the action spectrum of photosynthesis and the role of pigments in capturing light energy *Chlorophyll is important in photosynthesis (Sachs) -​ He linked chlorophyll distribution to areas of carbohydrate production, reinforcing its role as a light-capturing molecule. *O2 came from H2O (van Niel and Robin Hill) -​ Van Niel proposed the concept while Robin Hill’s experiment confirmed that water is the source of oxygen, transforming the understanding of the photosynthetic process * Final Electron acceptor in photosynthesis is NADP+ (contemporary botanist)  -​ Modern research shows that the final electron acceptor is NADP+, forming NADPH. The compound is crucial for driving the Calvin cycle, and synthesizing sugars Photosynthesis -​ An anabolic, endergonic, carbon dioxide-requiring process that uses light energy (photons) and water(H2O) to produce organic macromolecules (glucose) -​ Photosynthesis is a redox process (Water is oxidized, and carbon dioxide is reduced) -​ The complete equation for photosynthesis -​ (6CO2+ 12H2O + light energy = C6H1206 + 6O2 +6H2O) Oxidation -​ Adding O -​ Removing H -​ Loss of electron -​ Release energy -​ Exergonic Reduction -​ Removing O -​ Adding H -​ Gain of electron -​ Stores energy -​ Endergonic The fate of the reactants in photosynthesis Reactant 6 CO2 12H2O Products C6H12O6 6H2O 6O2 Where does photosynthesis take place? In all photoautotrophic organisms a.​ Mosses, ferns, and flowering plants b.​ Kelp c.​ Euglena d.​ Cyanobacteria Trees do not produce nearly as much oxygen -​ This is because trees use up energy/oxygen for other functions, eg. growth The Sites of Photosynthesis ​ All organs with photosynthetic pigments ​ In true plants, the leaves are the major sites of photosynthesis  ​ Stomata light abiding for plants that absorb carbon dioxide and release oxygen TWO PROCESSES ​ Light Processes - (light-dependent, photochemical processes produce oxygen) ​ Dark processes - (light-independent or carbon fixation process, produces glucose) Light Reactions Conversions of light (solar) energy to chemical energy (ATP and NADPH) Light -​ Consists of certain particles called photons: each photon has a fixed quantity of energy -​ It is a form of electromagnetic energy which travels in waves -​ The distance between the crests of waves (= wavelength) determines the electromagnetic energy -​ The entire energy of electromagnetic energy, or radiation, is called the electromagnetic spectrum -​ Plants can absorb light between UV and infrared; all visible light -​ Sunlight is a mixture of many wavelengths -​ During the light reaction, when light or photon hits the Thilacoid or the bramium of the chlorophyll, water will enter the light reaction and produce oxygen, ATP, nadph -​ The ATP and NADPH are needed for the Calvin cycle The visible light spectrum -​ Includes the colors of light we can see (=reflected radiation) -​ Includes the wavelengths that drive photosynthesis -​ Photosynthesis pigments absorb the visible spectrum