 | Light Reactions of Photosynthesis Simulation of the light reactions of photosynthesis |
 | Light (Dependant) Reactions of Photosynthesis Animation Photosynthesis takes the human/animal waste product carbon-dioxide (CO2) and in the presence of light and water creates the things we need for cellular respiration, oxygen and glucose. See the following links: Cellular Respiration - http://www.youtube.com/watch?v=OqSnts1C_0g Calvin Cycle - http://www.youtube.com/watch?v=VFp-4vo6Ch8 Light and Pigments - http://www.youtube.com/watch?v=OUUsKXR27rs The initial stage of the photosynthetic system is the light-dependent reactions, which convert light -solar energy- into chemical (potential) energy. The light dependent reactions specifically produce oxygen gas and convert ADP into ATP and NADP+ into NADPH. Organisms form the kingdom Plantae usually use noncyclic(do not reCYCLE same electrons) photophosphorylation, a two-stage process involving two different chlorophyll photosystems. First, light strikes a plant, specifically a cell. This cell has an organelle(s) called a chloroplast that gives photosynthetic cells their characteristic green color. Chloroplasts have structures called stroma. Stroma are full of hollow disks (similar to a whoopie cushion) called thylakoids arranged in stacks call grana. There are membrane proteins implanted into the surface of the thylakoid called photosystem II and photosystem I that have a pigment called chlorophyll located on the top of these proteins.***Photo System I comes second, but was discovered first and Photo System II was found second and named for that reason even though it comes first.*** Light particles, called photons, strike the electrons located in the chlorophyll of photo system II, Now in an excited state, they travel along the thylakoid membrane to photo system I where they are re-excited by photons again moving them to the acceptor molecule NADP+. The flow of electrons through the membrane proteins creates a concentration gradient, also known as proton motive force, which drives ATP synthesis through chemiosmosis (see http://www.youtube.com/watch?v=Btl0ltsw4m0). The electrons originally lost in Photo System II must be replaced. A water molecule is broken down into 2H+ + 1/2 O2 + 2e- by a process called photolysis (or light-splitting). The two electrons from the water molecule replenish electrons lost in photosystem II's chlorophyll. Meanwhile the 2H+ and 1/2O2 are left out for further use. The photosystem II complex replaced its lost electrons from an external source, however, the two other electrons are not returned to photosystem II as they are in the analogous cyclic pathway(prokaryotes like cyanobacteria). The highly excited electrons are transferred to the acceptor molecule, but this time are passed on to an enzyme called Ferredoxin- NADP reductase(NADP+ reductase), for short FNR, which uses them to catalyze the following reaction (as shown): NADP+ + 2H+ + 2e- → NADPH + H+ This consumes the H+ ions produced by the splitting of water, leading to a net production of 1/2O2, ATP, and NADPH+H+ with the consumption of the light(photons) and water. Next are the dark reactions(not light dependant)... The Calvin Cycle - http://www.youtube.com/watch?v=VFp-4vo6Ch8 |
 | Photosynthesis the Movie An in depth look at photosynthesis with added humor |
 | Light Dependent Reactions Light Dependent Reactions |
 | Photosynthesis - The Light Reactions This music video teaches the overall reactions of photosynthesis, with a particular focus on the light reactions. The level is freshman or AP Biology. While still a work in progress (produced without access to a video camera!), I decided to publish this to help students review for the AP Biology exam. Lyrics can be purchased. Please email me at photosynthesismovie@gmail.com |
 | Bio: Light Dependent Reactions corie and ann |
 | PHOTOSYNTHESIS phtotsynthesis |
 | Photosynthesis PowerPoint Presentation |
 | The Calvin Cycle or "Dark" Reactions (Photosynthesis) Watch Carbon Dioxide become sugar! Overview During photosynthesis, light energy is used to generate chemical free energy, stored in glucose. The light-independent Calvin cycle, also (misleadingly) known as the "dark reaction" or "dark stage", uses the energy from short-lived electronically-excited carriers to convert carbon dioxide and water into organic compounds that can be used by the organism (and by animals which feed on it). This set of reactions is also called carbon fixation. The key enzyme of the cycle is called RuBisCO. In the following equations, the chemical species (phosphates and carboxylic acids) exist in equilibria among their various ionized states as governed by the pH. The enzymes in the Calvin cycle are functionally equivalent to many enzymes used in other metabolic pathways such as gluconeogenesis and the pentose phosphate pathway, but they are to be found in the chloroplast stroma instead of the cell cytoplasm, separating the reactions. They are activated in the light (which is why the name "dark reaction" is misleading), and also by products of the light-dependent reaction. These regulatory functions prevent the Calvin cycle from operating in reverse to respiration, which would create a continuous cycle of carbon dioxide being reduced to carbohydrates, and carbohydrates being respired to carbon dioxide. Energy (in the form of ATP) would be wasted in carrying out these reactions that have no net productivity. The sum of reactions in the Calvin cycle is the following: 3 CO2 + 6 NADPH + 5 H2O + 9 ATP → C3H5O3-PO32- + 2 H+ + 6 NADP+ + 9 ADP + 8 Pi OR 3 CO2 + 6 C21H29N7O17P3 + 5 H2O + 9 C10H16N5O13P3 → C3H5O3-PO32- + 2 H+ + 6 NADP+ + 9 C10H15N5O10P2 + 8 Pi It should be noted that hexose (six carbon) sugars are not a product of the Calvin cycle. Although many texts list a product of photosynthesis as C6H12O6, this is mainly a convenience to counter the equation of respiration, where six-carbon sugars are oxidized in mitochondria. The carbohydrate products of the Calvin Cycle are three-carbon sugar phosphate molecules, or "triose phosphates," specifically, glyceraldehyde-3-phosphate. |
 | Photosynthesis-Calvin Cycle and Cyclic Electron Flow WATCH THIS IN HIGH QUALITY SO YOU CAN SEE THE CALVIN CYCLE DIAGRAM. This video is the second of two parts. Part A examined the light reactions. This part provides, in music and rhyme, a detailed explanation of the Calvin Cycle and Cyclic electron flow. Lyrics are available for purchase at photosynthesismovie@gmail.com |
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