photosynthesis

• In the dark, photosynthesis is inactive and plants much undergo cellular respiration to harness energy
• When light is present, plants favor photosynthesis over cellular respiration
• Higher concentrations of H+ ions correspond to a lower pH and a more yellow color on the Bromothymol blue pigment
• good ia ideas: https://www.labxchange.org/library/items/lb:LabXchange:0cf2328b:lx_simulation:1?fullscreen=true
• Plants are photoautotrophs: using the energy of sunlight to sustain themselves
• Photosynthesis is a light-based energy generation process used by photoautotrophs with chloroplasts
• Chlorophyll best absorbs red (400-500) and blue (600-700) light through its light-absorbing "head" (porphyrin ring) and green (500-600) light is most commonly transmitted.

  
• Pigments in chloroplasts include Chlorophyll A (the main pigment), Chlorophyll B (accessory pigment), and minor cartenoids, xanthophyl, and pheothtins

  
• The visible light spectrum is created through the dispersion of white light because of its internally differentiating frequencies
• Through photosynthesis, 6 molecules of carbon dioxide and 6 molecules of water is used to create 1 molecule of glucose and 6 molecules of oxygen- this is a light independent reaction. The glucose will be chemically converted into energy
• A light dependent reaction in photosynthesis includes photolysis occurs- the splitting of two molecules of water, using light, to create oxygen, electrons and protons (2H2O --> 4e- + 4H+ + O2)
• Electrons created through photolysis are used to replace the displaced electrons lost in the Reaction Center chlorophyll during photoactivation of Photosynthesis II
• photolysis occurs in the photosystem II in the thylakoid
• the thylakoid is a stack of membranes in a chloroplast cellular structure
• Protons created in photolysis are part of the proton gradient of the thylakoid lumen that help make ATP through chemiosmosis
• Photolysis was thought to be a process necessary for photosynthesis when they tested different oxygen isotopes to trace back its origin in photosynthesis and found it to be sourced from water, not carbon dioxide
• The first step of light dependent reaction is photo-excitation as light hits the photosystem II in the thylakoid
• The electrons in Photosystem II to circle the membrane with set chlorophyll pigments and then be accepted by the primary electron acceptor in the middle of Photosystem II so that when photo-excitation occurs, the electrons are excited and pass along other membranes called the electron transport chain to Photosystem I where it is no longer excited. This process released energy into the thylakoid membrane and prompts proton migration to the thylakoid space
• The electron in Photosystem II is now in Photosystem I so the third light-dependent reaction, Photolysis, creates electrons to replace the missing electron in Photosystem II.
• The fourth step of light-dependent photosynthesis is chemiosmosis photophorylation where the thylakoid uses the energy from its electron migration to use the ATP synthase to push protons towards the inner stroma space.
• The fifth step of light-dependent photosynthesis uses the migrated protons to reduce ADP into ATP
• Eventually, light hits photosystem I and excites the priorly depleted electron, starting the fifth step of the light dependent reaction by carrying it across the second electron transport chain which eventually leads into the stroma space. The electron is then used to reduce NADP+ into NADPH
• NADPH is then used alongside Carbon dioxide and water to synthesize glucose and oxygen
• Glucose is C6H12O6
• As enzymes are heavily relied upon in photosynthesis, the process itself has an optimal temperature at which it functions the best
• The concentration of H2O and CO2 increases rate of photosynthesis until all enzymes used in photosynthesis are occupied and the reactants are both in excess
• Increases in light intensity increases the rate of photosynthesis until the point at which all pigments are working at full capacity and light becomes excess
• The limiting factor of photosynthesis can be pinpointed when all other factors are at their favorable or optimal conditions
• The absorption spectrum shows the relative amount of light absorbed at each wave length (color) by the different pigments in the plant- this is good to spot the effectiveness of different lights on different pigments but generally, they show highest absorptions at red and blue and lowest at green
• The action spectrum shows the relative effectiveness of photosynthesis at absorption of different wavelengths (colors) as an average for ALL pigments with the least activity at green and the most at blue and red
• Not all photosynthetic organisms have the same action and absorption spectrum
• To experimentally test the wavelengths absorbed and released, white light can be diffracted through a prism and one color can be allowed to pass through a solution of chlorophyll. There the amount of light transmitted can be measured through a photoelectric tube and interpreted through a galvanometer measuring changes in electrical current (low transmittance = high absorbance and vise versa of that specific color)
• If a plant like a pondweed is placed upside down in water with its stem cut, it can be trapped in a funnel with an inverted test tube at its end to collect oxygen and measure the presence of photosynthesis in the plant, given that a stable, strong light source is provided to the plant, the funnel and vessel are transparent, and a source of CO2, such as NaHCO3 is added to the water for the plant to absorb and photosynthesize

  
• Plant roots have some salts/solutes in them so they attract water from the soil to them. They have cell walls that prevent them from bursting as turgor pressure in cell is high and cell expands and refuses any more water
• When plant cells are not salty, they are hypotonic and grow flaccid and shriveled