chapter 6 outline
chapter 6 outline BIOL 1110
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This 7 page Class Notes was uploaded by Caitrín Hall on Tuesday January 26, 2016. The Class Notes belongs to BIOL 1110 at University of Connecticut taught by Bernard Goffinet in Summer 2015. Since its upload, it has received 16 views. For similar materials see Introduction to Botany in Biology at University of Connecticut.
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Date Created: 01/26/16
Photosynthesis and Respiration 61 Photosynthesis and respiration are the processes by which living organisms capture solar energy and release it to sustain life on Earth Photosynthesis process by which organisms capture solar energy and use it to produce carbs 6C0 12HOifrCH 0 60 6HO 2 2 6 12 6 2 2 0 Solar energy is captured in covalent bonds of simple sugars Respiration process by which organisms release energy from carbs and other organic molecules CH O60i11f6CO 6HO 612 6 2 2 2 0 Signi cant amount of energy transferred to ATP where it is used in biochemical reactions throughout the metabolism Metabolism sum of all chemical reactions within an organism 62 Metabolism includes many kinds of chemical reactions organized into series called pathways Metabolism chemical reactions Directed by enzymes require or release energy 0 Exergonic potential energy of substrates gt products release energy occur spontaneously respiration o Endergonic potential energy of products gt substrates require energy input many reactions in photosynthesis 0 ATP carries excess energy from exergonic to endergonic Covalent bond between last two phosphate groups contain much energy Another molecule is phosphorylated amp energized for another reaction Allows endergonic reactions to occur spontaneously ATP l ADP l AMP 0 Many involve electron transfer oxidationreduction o Oxidation ls Loss 0 Reduction ls Gain 0 Proton H usually travels with electron to transfer hydrogen atom amp its potential energy l electron acceptor molecule Nicotinamide adenine dinucleotide NAD respiration Nicotinamide adenine dinucleotide phosphate NADP photosynthesis Electron transport chain series of electron acceptors each molecule is reduced when it receives an electron amp oxidized when it passes it Electron energy level drops used as heat amp powers metabolic reactions Occur in series or pathways 0 Cycles chains branches 63 Photosynthesis harvests solar energy to sustain life on Earth I Photosynthesis created today s atmosphere by turning methane amp C02 to oxygen 0 Lightpigment interaction is crucial O Visible light 400700nm of electromagnetic spectrum I Light behaves like photons amp waves I Longer wavelength I lower energy red I Enough energy to excite electrons of organic materials I Electron goes from low to high energy excited state when it absorbs visible light energy 1 Energy is emitted as heatlight 2 Energy is transferred to another molecule 3 Electron is transferred to electron acceptor O Pigments absorb light I Chlorophyll 1 re ects green I Absorption spectrum shows chlorophyll a absorbs red amp blueviolet I Accessory pigments chlorophyll b amp carotenoids absorb other colors I Occurs in chloroplasts 0 Flat platelike thylakoids solar energy converted to ATP and NADPH are embedded in viscous uid stroma C02 reduced to simple sugar 0 Contained in mesophyll cells inside leaves I Sunlight CO2 H2O meet I CO2 enters leaf through stomata pores 0 Light energy I chemical energy stored in sugars 0 Light reactions capture solar energy 0 Electrons in thylakoids become excited 1 Some energy splits H2O to release 02 2 ATP captures some energy 3 Electron and H convert NADP to NADPH O Photosystems I and II I Groupings of proteinspigment molecules I Contain an antenna complex accessory pigment molecules and a reaction center Begins in II 1 Accessory pigment absorbs light 2 Transfers to P680 3 Leaves chlorophyll a to join electron acceptor 4 Water splits into 02 protons and electrons photolysis 5 Electron travels down chain Continues in I 1 Electron transfers to chlorophyll a molecule in P700 reaction center to replace previously excited electron 2 Enters second chain 3 NADP electron H proton I NADPH Noncyclic electron flow 0 8 photons absorbed 4 enter noncyclic ow I 3 ATP amp 2 NADPH Cyclic electron flow 0 Only in photosystem I 0 No photolysis or NADPH 0 Provides ATP for carbonfixation reactions 0 Photophosphorylation Excited electron energy pumps H protons into lumen H from photolysis enters lumen Lumen becomes acidic Electrochemical gradient installed Fuels ATP formation Protons ow back to stroma through ATP synthase complex chemiosmosis 0 4 protons I 1 ATP 0 Carbonfixation reactions reduce carbon dioxide to simple sugars 0 Calvin cycle C3 pathway 0 Begin in stroma with ATP and NADPH l 2 3 4 Rubisco carboxylaseoxygenase enzyme attaches RuBP SC to CO2 6C sugar splits into two 3C molecules of 3phosphoglycerate PGA PGA uses energy and power from ATP and NADPH to become PGAL phosphoglyceradehyde PGAL regenerates RuBP using ATP or becomes sugar gt Cycle turns 6 times to produce 1 molecule of glucose 2 PGAL 12 NADPH 18 ATP 64 photons of light 0 Photorespiration makes process inefficient Excessive heatlight increases photosynthesis which calls for more CO2 but stomata close to avoid water loss Metabolic process in which rubisco combines with 02 instead of CO2 and produces only one PGA instead of two 0 C4 pathway Separate C4 amp Calvin cycle in space First product of carbonfixation is oxaloacetate 4C No Calvin cycle in mesophyll cells C02 combines With 3C compound phosphoenolpyruvate PEP to form oxaloacetate 0xaloacetate reduces to malate Which enters bundle sheath cells and 3C pyruvate C02 is released and fixed again in Calvin cycle 3C pyruvate becomes PEP with energy from ATP 0 Crassulacean Acid Metabolism CAM plants Separate C4 amp Calvin cycle in time Stomata close during day fix C02 at night Stored as malic acid C4 in vacuole Malic acid enters cytoplasm as malate at dawn as stomata close Malate becomes C02 and pyruvate C02 enters chloroplasts and undergoes Calvin cycle 64 Respiration and fermentation release energy for cellular metabolism Respiration Metabolic process by Which glucose is broken down in the presence of oxygen into C02 and water Energy released is captured in ATP Glycolysis I acetyl coenzyme A formation I Krebs cycle I electron transport chain I chemiosmosis and oxidative phosphorylation 0ccurs in cytoplasm and mitochondria Glycolysis 0ccurs in cytoplasm Splitting of glucose into two molecules of pyruvate C3 H3 03 Net gain of 2 ATPglucose amp 2NAD I NADH from excess H protons No 02 required anaerobic O O O O Fermentation O Extracts energy from organic compounds Without oxygen 0 Pyruvate becomes ethyl alcohol and C02 0 NADH becomes NAD Aerobic conditions 2nd and 3rd decarboxylations More energy released Respiration breaks down particles through formation of acetyl CoA 1st decarboxylation 0 Pyruvate enters matrix of mitochondria Where it splits into C02 and a 2carbon acetyl group I Coenzyme A CoA and acetyl group form acetyl CoA 0 Energy is captured each time NAD is reduced to NADH I Krebs cycle citric acid cycle 0 Starts With 2 molecules of acetyl CoA for each glucose 0 Each acetyl CoA enters by transferring acetyl group to oxaloacetate 4C molecule 0 Yields 6C molecule of citrate I H protons are used to reduce NAD and FAD to NADH and FADH2 captures most of energy 0 Little energy is captured in ATP 0 One glucose yields 2 ATP 6 NADH 2 FADH2 I At this point 6 CO2 have been released 10 NADH amp 10 H formed 4 ATP 2 FAH2 0 Electron transport chain 0 O O 0 Located in cristae NADH and FADH2 must be converted to ATP to be used Carrier molecules take high energy electrons from NADH and FADH2 and transport them down chain through series of oxidationreduction reactions Electron releases energy I Dissipated as heat I Used to move protons to intermembrane becomes acidic I Build up of protons creates electrochemical gradient 0 Chemiosmosisoxidative phosphorylation O O O O 0 Generate ATP Electrochemical gradient is accessed through ATP synthase complex Chemiosmosis ow of protons from intermembrane to matrix through ATP synthase complex Proton energy is captured by converting ADP to ATP oxidative phosphorylation I Oxygen is final acceptor in chain Role of ATP is CRUCIAL 38 produced from 1 molecule of glucose Chapter Wrapup Examine and Discuss Self Test 1 The absorption spectrum shown in Figure 610 indicates that chlorophyll a mainly absorbs light energy in what part of the visible light spectrum b yellow and red c red and green d orange and green e yellow and green Accessory pigments in the antenna complex absorb light at different wavelengths than chlorophyll a According to the absorption spectrum in Figure 610 carotenoids absorb best in what part of the visible spectrum a orange b yellowgreen c violet e yellow through red The key structure generating ATP in the photosynthetic light reactions is a the Calvin cycle c the antenna complex d Photosystem l e the reaction center Which of the following best describes the end products of photosynthesis I b ADP NADP and PGAL c ATP NADH and pyruvate d ATP NADH FADHZ and co2 Plants that use the C4 pathway are not subject to the inefficiencies of photorespiration as are C3 plants Why do C4 plants not displace C3 plants in the environment a C4 plants cannot tolerate freezing temperatures b C4 plants can only x carbon dioxide into simple sugars at night c C4 plants are better adapted to hot dry weather and higher light levels than C3 plants I F Yeasts carrying out alcohol fermentation would produce which of the food products listed below a cheese b pickles d soy sauce e yogurt 7 Which of the following respiration processes occurs in the mitochondrial matrix a chemiosmosis b glycolysis d electron transport chain e Krebs cycle Applying Concepts 1 Many people believe that plants do not need to obtain any energy at all from respiration because they are photosynthetic Give some examples of where and when plant cells do use respiration to obtain the ATP energy they need Energy released during glycolysis is captured in ATP bonds Fermentation extracts energy from organic compounds Energy is released in each decarboxylation during aerobicanaerobic processes 2 The reaction of respiration including glycolysis the Krebs cycle electron transport and the generation and harvesting of a proton gradient to phosphorylate ADP to ATP are accomplished in a series of small steps Why do biological systems use such an incremental approach rather than just completing the oxidation in a couple of large steps This makes it possible to capture the energy in the chemical bonds of glucose If burning of sugar happened in one step all energy would be dissipated as heat
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