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Unformatted text preview: PHOTOSYNTHESIS PHOTOSYNTHESIS Photosynthesis • Anabolic (small molecules combined) • Endergonic (stores energy) • Carbon dioxide (CO2) requiring process that uses light energy (photons) and light water (H2O) to produce organic water macromolecules (glucose). macromolecules photons SUN 6CO2 + 6 H2O → C6glucose + 6 O2 H12O6 2 Question: Where does Where photosynthesis take place? take 3 Plants • Autotrophs – produce their own food Autotrophs (glucose) (glucose) • Process called photosynthesis Process photosynthesis • Mainly occurs in the leaves: Mainly leaves: a. stoma - pores b. mesophyll cells Mesophyll Cell Chloroplast Stoma 4 Stomata (stoma) Pores in a plant’s cuticle through which water vapor and gases (CO2 water gases (CO & O2) are exchanged between the plant and the atmosphere. plant Oxygen (O2) Stoma Carbon Dioxide (CO2) Guard Cell Guard Cell Found on the underside of leaves 5 Mesophyll Cell of Leaf Nucleus Cell Wall Chloroplast Central Vacuole Photosynthesis occurs in these cells! 6 Chloroplast Organelle wh e re photosynthesis ta ke s p la c e . Stroma Outer Membrane Inner Membrane Thylakoid Granum Thylakoid stacks are connected together 7 Thylakoid Thylakoid Membrane Granum Thylakoid Space Grana make up the inner membrane 8 Question: Why are Why plants green? green? 9 Chlorophyll Molecules • Located in the thylakoid membranes Located thylakoid • Chlorophyll have Mg+ in the center Chlorophyll Mg • Chlorophyll pigments harvest energy Chlorophyll (photons) by absorbing certain (photons) wavelengths (blue-420 nm and red-660 nm are most important) nm • Plants are green because the green Plants green wavelength is reflected, not absorbed. wavelength 10 11 Wavelength of Light (nm) 400 500 600 700 Short wave Long wave (more energy) (less energy) 12 Absorption of Light by Absorption Chlorophyll Chlorophyll Chlorophyll absorbs blue-violet & red light best Absorption violet blue green yellow wavelength orange red 13 Question: During the fall, what During causes the leaves to change colors? to 14 Fall Colors • In addition to the chlorophyll In pigments, there are other pigments other present present • During the fall, the green chlorophyll During pigments are greatly reduced pigments revealing the other pigments revealing • Carotenoids are pigments that are either red, orange, or yellow red orange or yellow 15 Redox Reaction The transfer of one or more The transfer electrons from one reactant to electrons another another Two types: 1. Oxidation is the loss of eOxidation loss 2. Reduction is the gain of eReduction gain 16 Oxidation Reaction The loss of electrons from a The loss substance or the gain of oxygen. oxygen. Oxidation 6CO2 + 6H2O → C6H12O6 + 6O2 glucose Carbon Carbon dioxide dioxide Water Oxygen 17 Reduction Reaction The gain of electrons to a The gain substance or the loss of oxygen. oxygen. Reduction 6CO2 + 6H2O → C6H12O6 + 6O2 glucose 18 Question: Why do cells Why use for energy? energy? 19 Energy for Life on Earth • Sunlight is the ULTIMATE energy for all life on Earth • Plants store energy in the chemical bonds of sugars • Chemical energy is released as ATP during cellular respiration 20 Structure of ATP • ATP stands for adenosine triphosphate • It is composed of the nitrogen base ADENINE, the pentose (5C) sugar RIBOSE, and three PHOSPHATE groups • The LAST phosphate group is bonded with a HIGH ENERGY chemical bond • This bond can be BROKEN to release ENERGY for CELLS to use 21 Removing a Phosphate from ATP Breaking the LAST PHOSPHATE bond from ATP, will --– Release ENERGY for cells to use – Form ADP – Produce a FREE PHOSPHATE GROUP 22 High Energy Phosphate Bond 23 FREE PHOSPHATE can be re-attached to FREE ADP reforming ATP ADP Process called Phosphorylation Process Phosphorylation 24 Phosphorylation 25 Parts of Parts Photosynthesis Photosynthesis 26 Two Parts of Photosynthesis Two reactions make up Two photosynthesis: photosynthesis: 1.Light Reaction or Light Light Dependent Reaction Dependent Produces energy from solar power (photons) in the form of ATP and NADPH. ATP SUN 27 Two Parts of Photosynthesis 2. Calvin Cycle or Light 2. Independent Reaction • Also called Carbon Fixation Also Carbon or C3 Fixation • Uses energy (ATP and ATP NADPH) from light reaction to NADPH from make sugar (glucose). (glucose). 28 Light Reaction (Electron Flow) • Occurs in the Thylakoid Occurs membranes membranes • During the light reaction, there are During light there two possible routes for electron two flow: flow: A. Cyclic Electron Flow B. Noncyclic Electron Flow 29 Cyclic Electron Flow • Occurs in the thylakoid membrane. Occurs thylakoid • Uses Photosystem I only Uses Photosystem • P700 reaction center- chlorophyll a • Uses Electron Transport Chain (ETC) Uses (ETC) • Generates ATP only Generates ATP ADP + ADP P ATP 30 Cyclic Electron Flow Primary Electron Acceptor SUN ee- ePhotons P700 e- ATP produced by ETC Accessory Pigments Photosystem I Pigments absorb light energy & excite e- of Pigments Chlorophyll a to produce ATP 31 Noncyclic Electron Flow • Occurs in the thylakoid membrane Occurs thylakoid • Uses Photosystem II and Uses Photosystem I Photosystem • P680 reaction center (PSII) P680 (PSII) chlorophyll a chlorophyll • P700 reaction center (PS I) (PS chlorophyll a chlorophyll • Uses Electron Transport Chain Uses (ETC) (ETC) • Generates O2, ATP and NADPH Generates 32 Noncyclic Electron Flow Primary Electron Acceptor Primary Electron Acceptor SUN Enzyme Reaction 2e- H2O 1/2O2 + 2H+ 2e- ETC 2e- 2e- Photon 2e- P700 NADPH ATP P680 Photon Photosystem I Photosystem II H2O is split in PSII & ATP is made, while the energy carrier NADPH is is made in PSI made 33 Noncyclic Electron Flow • ADP + P → ATP ATP • NADP+ + H → NADPH NADPH • Oxygen comes from the splitting of H2O, not CO2 of H2O → 1/2 O2 + 2H+ 34 Chemiosmosis • Powers ATP synthesis Powers ATP • Takes place across the thylakoid Takes membrane membrane • Uses ETC and ATP synthase Uses ETC (enzyme) (enzyme) • H+ move down their concentration gradient through channels of ATP synthase forming ATP from ADP synthase ATP 35 Chemiosmosis SUN H+ H+ Thylakoid E PS II (Proton Pumping) T PS I C high H+ HH concentration + H+ H+ H+ H + H ADP + P + H+ + ATP Synthase ATP Thylakoid Space low H+ concentration 36 Calvin Cycle • Carbon Fixation (light independent Carbon reaction) reaction) • C3 plants (80% of plants on earth) • Occurs in the stroma stroma • Uses ATP and NADPH from light Uses ATP reaction as energy reaction • Uses CO2 Uses CO • To produce glucose: it takes 6 To glucose it turns and uses 18 ATP and 12 NADPH. 37 Chloroplast STROMA– where Calvin Cycle occurs Outer Membrane Inner Membrane Thylakoid Granum 38 Calvin Cycle (C3 fixation) (36C) 6C-C-C-C-C-C (6C) 6CO2 (unstable) 6C-C-C 6C-C-C 12PGA (36C) 6ATP 6NADPH (30C) 6C-C-C-C-C RuBP (30C) glucose 6NADPH 6C-C-C 6ATP C3 6ATP (36C) 6C-C-C 12G3P (6C) C-C-C-C-C-C9 3 Glucose Calvin Cycle Remember: C3 = Calvin Cycle C3 Glucose 40 Photorespiration • Occurs on hot, dry, bright days • Stomates close • Fixation of O2 instead of CO2 • Produces 2-C molecules instead of Produces 3-C sugar molecules 3-C • Produces no sugar molecules or no Produces no ATP ATP 41 Photorespiration Because of photorespiration, plants Because have special adaptations to limit the effect of photorespiration: effect 1. C4 plants 2. CAM plants 42 C4 Plants • Hot, moist Hot, environments environments • 15% of plants 15% (grasses, corn, grasses, sugarcane) sugarcane) • Photosynthesis Photosynthesis occurs in 2 places occurs • Light reaction mesophyll cells mesophyll • Calvin cycle - bundle sheath cells sheath 43 C4 Plants Malate-4C sugar C-C-C-C Malate C-C-C-C Transported CO2 CO2 C3 Vascul glucose Tissu C-C-C PEP ATP Mesophyll Cell C-C-C Pyruvic Acid Bundle Sheath Cell 44 CAM Plants • Hot, dry environments • 5% of plants (cactus and ice plants) plants) • Stomates closed during day • Stomates open during the night • Light reaction - occurs during the Light day day • Calvin Cycle - occurs when CO2 is present present 45 CAM Plants Night (Stomates Open) Day (Stomates Closed) Vacuole CO2 C-C-C-C Malate C-C-C-C Malate C-C-C-C Malate CO2 C-C-C PEP ATP C-C-C Pyruvic acid C3 glucose 46 Question: Why do CAM Why plants close their stomata during the day? the 47 Cam plants close their stomata in the hottest part of the day to conserve water conserve ...
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This note was uploaded on 11/09/2011 for the course BIO 110 taught by Professor Harmon during the Winter '11 term at BYU.

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