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Photosynthesis & Cellular Respiration Energy & Living Things, Photosynthesis and Cellular Respiration Chapter 5

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Photosynthesis & Cellular Respiration

Photosynthesis&Cellular Respiration Energy & Living Things, Photosynthesis and Cellular RespirationChapter 5Energy in Living ThingsBuilding Molecules That Store EnergyMetabolism: builds and breaks moleculesPhotosynthesis: conversion of light energy into chemical energyAutotrophs: organisms that use sunlight or inorganic molecules to produce organic matterThese organisms include: Plants use sunlightProkaryotes use chemicals flowing out of earth vents on the ocean floorBreaking Down Food for EnergyChemical energy can also be transferred from one organic compound to anotherEx. Hydrolysis using water to break bondsHeterotrophs: organisms who receive chemical energy from consuming organic matterCellular respiration: releases energy that is contained in food to convert it to ATP (another form of energy)ATP is the source of energy for cells to carry out their daily activities for an organism to surviveTransfer of Energy to ATPSimilar to burning coal or wood for heatFood energy is released in a series of enzyme-assisted chemical reactionsThe product from the previous reaction becomes the reactant in the next reaction until ATP is createdExample:Starch is broken down into glucose and glucose is broken down into Carbon Dioxide & WaterDuring the reaction: heat is released



Stage One: Absorption of Light EnergyLight Dependent ReactionsPigmentsLight absorbing substancesAbsorb only certain wavelengths and reflect all othersChlorophyll: absorbs blue & red, reflects green & yellowPlants contain chlorophyll, chlorophyll a & chlorophyll bCarotenoids: produce yellow and orange colorsAbsorbs and reflect different wavelengths than chlorophyllEnables plants to absorb more light during photosynthesis

Stage One: ContinuedProduction of OxygenThylakoids: disk-shaped structure containing of clusters of pigments in the chloroplast of the cellLight strikes the thylakoids, energy is transferred to electrons and electrons move to higher levelsElectrons move from chlorophyll to nearby molecules to initiate stage two of photosynthesis.These electrons are replaced by water moleculesStage Two: The Conversion of Light EnergyElectron Transport Chain (ETC): a series of molecules that electrons pass through along the thylakoid membraneWorks around a concentration gradient Hydrogen ions lose energy when they channel through a protein when the concentration builds within the cell, the ions diffuse outThe ions are recharged when they assist in adding a phosphate group to ADP to make ATP (first ETC)In the 2nd ETC, electrons combine with hydrogen ions to create NADPH from NADP+NADPH: electron carrier that provides high-energy electrons for stage three of photosynthesisLook at the summary at end of this stage10

Stage Three: Storage of EnergyPurpose: production of organic compounds from carbon atoms Carbon Dioxide Fixation: transfer of carbon dioxide to organic compounds (light-independent reaction)Calvin CycleA CO2 molecule added to a five-carbon compound (3)Three 6-C compounds split into six 3-C compoundsOne 3-C sugar is used to make organic compoundFive 3-C compounds are cycled throughDraw Calvin Cycle12Factors That Affect PhotosynthesisIncreaseLight Intensity Increases (until saturation)Carbon Dioxide concentration (until max)DecreaseSlowed by the Calvin CycleUnfavorable conditions for enzymesCellular Respiration Cellular EnergyAerobic: metabolic processes that require O2Anaerobic: metabolic processes that do not require O2Equation of Cellular Respiration:

Stage One: Breakdown of GlucoseGlycolysis: enzyme assisted anaerobic process that breaks down 6-C glucose into two 3-C pyruvate ionsStep 1: In 3 rxns, phosphate groups from 2 ATP are transferred to a glucose molecule

Stage One: Breakdown of GlucoseStep 2: In 2 rxns, glucose broken down into two 3-carbon compounds each with a phosphate

Stage One: Breakdown of GlucoseStep 3: Two NADH molecules are produced and one more phosphate group is transferred to each 3-C compound

Stage One: Breakdown of GlucoseStep 4: In 4 rxns, each 3-C compound pyruvate ion and four ATP molecules are produced

Summary of GlycolysisUses 2 ATP to beginProduces 4 ATPNet gain: 2 ATPGlucose (6-Carbons) Two 3-C pyruvate ionsNADH and NAD+ are recycled

Stage Two: Production of ATPOxygen present pyruvate is converted to a 2-carbon compound in the mitochondrionReaction produces:One molecule of CO2One molecule of NADHOne 2-C acetyl group attached to form acetyl-CoADraw Krebs Cycle20Krebs CycleA cycle beginning with acetyl-CoA to produce ATP

Step 1: Acetyl-CoA attached to a 4-C compound to form a 6-C compound and release CoA

Step 2: CO2 is released from 6-C compound forming a 5-C compound Electrons transferred to NAD+ to make NADHDraw Krebs Cycle21Krebs Cycle - ContinuedStep 3: Another CO2 is released forming a 4-C compound, an ATP molecule and NADH are produced

Step 4: 4-C compound converted to a different 4-C compound.Electrons transferred to FAD to produce FADH2

Step 5: 4-C compound converted to the original 4-C compound that started the cycleNADH producedDraw Krebs Cycle22Electron Transport ChainElectrons are donated from NADH & FADH2Located in the inner membrane of mitochondrion The energy of electrons are used to pump out hydrogen ionsConcentration gradient is created - causes hydrogen ions to be pumped into the membraneThe energy created adds a phosphate group to ADP to form ATPProducts include: ATP and water moleculesRespiration in the Absence of OxygenETC cannot function oxygen is the final electron acceptorNAD+ is recycled in other waysFermentation: recycling of NAD+ using another form of organic hydrogen acceptorLactic AcidAlcoholic

Lactic Acid Fermentation3-C pyruvate converted to 3-C lactate Lactate: ion of its organic acid lactic acidFormed during intense workoutsDuring the conversion:NAD+ and NADH are recycledNo FADH2Lactate expelled from musclesDraw on the board25Alcohol Fermentation3-C pyruvate broken down to ethanol (2-C compound)Step 1: Pyruvate is converted to 2-C compoundCarbon dioxide expelled Step 2: 2-C compound converted to ethanolDuring break down:NAD+ and NADH are recycledCarbon dioxide expelled

Draw on the board26