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Photosynthesis Photosynthesis
Energy TransformationsEnergy TransformationsATP ATP is the energy molecule used in all living things, so is the energy molecule used in all living things, so
supplies must be constantly replenished.supplies must be constantly replenished. energy must be added to make ATP, thus ATP energy must be added to make ATP, thus ATP
formation is an endergonic reaction.formation is an endergonic reaction. ADP + P + energy ---ADP + P + energy --- ATP ATP the addition of a phosphate molecule to ATP is the addition of a phosphate molecule to ATP is
called called phosphorylationphosphorylation ATP ---ATP --- ADP + P + energy ADP + P + energy the removal of a phosphate molecule from ATP the removal of a phosphate molecule from ATP
gives off energy and is called gives off energy and is called dephosphorylationdephosphorylation
Electron Transport System (ETS)Electron Transport System (ETS)
is the means by which energy production occurs within cells. It is is the means by which energy production occurs within cells. It is a series of progressively stronger electron acceptors. Each time a series of progressively stronger electron acceptors. Each time an electron is transported, energy is either released or absorbed.an electron is transported, energy is either released or absorbed.
This is how most of the This is how most of the ATPATP in plants and animals is formed in plants and animals is formed
Redox ReactionsRedox Reactions
Oxidation – loss of electrons, producing a substance with a more positive charge.
Reduction – gain of electrons, producing a substance with a more negative ( or less positive) charge.
PhotosynthesisPhotosynthesis Photosynthesis is the most important chemical Photosynthesis is the most important chemical
process on earth. Photosynthesis harnesses process on earth. Photosynthesis harnesses sunlight energysunlight energy and converts it into a form of and converts it into a form of energy (glucose and starch) that is useable by energy (glucose and starch) that is useable by all living organisms. The process also produces all living organisms. The process also produces oxygen, which is essential for higher life forms.oxygen, which is essential for higher life forms.
CO2CO2(g) (g) + H+ H22OO(l)(l) + light + light C C66HH1212OO6(s)6(s) + O + O2(g)2(g) + H + H22OO(l)(l)
Sunlight energy is converted into chemical potential energy (glucose)Sunlight energy is converted into chemical potential energy (glucose)
Site of PhotosynthesisSite of Photosynthesis
Photosynthesis occurs within the chloroplasts of plant cells, within the thylakoid membrane and the stroma.
ChloroplastsChloroplasts - contain the photosensitive - contain the photosensitive pigmentpigmentchlorophyllchlorophyll, which reflects green light., which reflects green light.
CaroteniodsCaroteniods – other accessory pigments that – other accessory pigments that absorb blue and violet light, but reflect yellow.absorb blue and violet light, but reflect yellow.
Stroma Stroma – interior space of the Chloroplast, The – interior space of the Chloroplast, The dark reaction occurs here.dark reaction occurs here.
Thylakoid diskThylakoid disk – photosynthetic membrane, – photosynthetic membrane, where the light reactionoccurs.where the light reactionoccurs.
Grana Grana – stacks of thylakoid disks.– stacks of thylakoid disks.LamellaeLamellae – unstacked thylakiods between – unstacked thylakiods between
grana.grana.
Stages of PhotosynthesisStages of PhotosynthesisLight Reactions – Thylakoid MembraneLight Reactions – Thylakoid Membrane
Stage 1Stage 1: Solar energy is captured and transferred : Solar energy is captured and transferred to the electrons, and water is split.to the electrons, and water is split.
PhotolysisPhotolysis – the splitting of water with light. – the splitting of water with light. 2H2H22O(l) + light ---O(l) + light --- 4H+(aq) + 4 e- + 4H+(aq) + 4 e- +
OO22(g)(g)
http://www.stolaf.edu/people/giannini/flashanimahttp://www.stolaf.edu/people/giannini/flashanimat/metabolism/photosynthesis.swft/metabolism/photosynthesis.swf
PhotosystemsPhotosystems
Within the chloroplasts, chlorophyll is Within the chloroplasts, chlorophyll is found in clusters within the thylakoid found in clusters within the thylakoid membranes. These clusters are called membranes. These clusters are called photosystems. When light hits the photosystems. When light hits the photosystem, energy is absorbed and photosystem, energy is absorbed and electrons are promoted to an electron electrons are promoted to an electron acceptor at a higher energy level. As the acceptor at a higher energy level. As the electrons fall down the electron transport electrons fall down the electron transport chain, energy is released and can be chain, energy is released and can be used to make ATP.used to make ATP.
NetLearning - Examples – Flash
Photosynthetic Electron Transport and ATP Synthesis
Stage 2: Stage 2: Electron transfer and the production of Electron transfer and the production of ATP.ATP.
Light energy is captured by the pigments within Light energy is captured by the pigments within the photosystems and is used to form more the photosystems and is used to form more stable energy rich molecules, and to make ATP stable energy rich molecules, and to make ATP from ATP and phosphate. This occurs by from ATP and phosphate. This occurs by cyclic photophosphorylationcyclic photophosphorylation and and chemiosmosis.chemiosmosis.
ChemiosmosisChemiosmosis – As H+ ions are pulled across – As H+ ions are pulled across the thylakoid membrane by the ETC, an the thylakoid membrane by the ETC, an concentration gradient of H+ ions is created. H+ concentration gradient of H+ ions is created. H+ ions travel down the concentration gradient, ions travel down the concentration gradient, across the membrane, through an ATP synthase across the membrane, through an ATP synthase complex. As they do this, ATP is produced.complex. As they do this, ATP is produced.
http://student.ccbcmd.edu/~gkaiser/biotutorials/http://student.ccbcmd.edu/~gkaiser/biotutorials/photosyn/hpumpp.htmlphotosyn/hpumpp.html
Animation of Chemiosmosis Proton PumpingAnimation of Chemiosmosis Proton Pumping
Dark Reactions – StromaDark Reactions – Stroma
Stage 3:Stage 3: Calvin Benson cycle and carbon fixation. Calvin Benson cycle and carbon fixation. The Calvin Benson cycle uses ATP, high energy The Calvin Benson cycle uses ATP, high energy
electrons, NADPH and CO2 to produce glucose electrons, NADPH and CO2 to produce glucose in the stroma. Sunlight energy is not required.in the stroma. Sunlight energy is not required.
RuBP, a 5 carbon sugar acts as a CO2 acceptorRuBP, a 5 carbon sugar acts as a CO2 acceptor The resulting 6 carbon sugar is split into two 3 The resulting 6 carbon sugar is split into two 3
carbon PGA molecules.carbon PGA molecules. Using H from NADPH, PGA is converted to PGALUsing H from NADPH, PGA is converted to PGAL PGAL can be used to produce glucose, starch, PGAL can be used to produce glucose, starch,
sucrose, glycerol or cellulose. sucrose, glycerol or cellulose. PGA can also be converted into amino acids or PGA can also be converted into amino acids or
fatty acids.fatty acids.
Calvin-Benson CycleCalvin-Benson Cycle
The Calvin Benson cycle must turn 3 times to produce each PGA molecule, and 6 times to produce one glucose molecule.The plant cell can manufacture all necessary organic compounds from the products of photosynthesis.
6CO2(g) + 12H2O(l) C6H12O6(s) + 6O2(g) + 6H2O(g)Calvin cycle
Photosynthesis Animated…Photosynthesis Animated…
PhotosynthesisPhotosynthesis photosynthesis dark phasephotosynthesis dark phase