1 photosynthesis energy & life. 2 overview of photosynthesis copyright cmassengale

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PhotosynthesisPhotosynthesis

Energy & Life

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Overview of Overview of PhotosynthesisPhotosynthesis

copyright cmassengale

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AutotrophsAutotrophs

Plants and some Plants and some other types of other types of organisms that organisms that contain contain chlorophyllchlorophyll are are able to use able to use light light energy from the energy from the sunsun to produce to produce food.food.


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AutotrophsAutotrophs• Autotrophs Autotrophs

include include organismsorganisms that that make their own make their own foodfood

• Autotrophs can Autotrophs can use the sun’s use the sun’s energy directlyenergy directly

EuglenaEuglena


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HeterotrophsHeterotrophs• Heterotrophs Heterotrophs

are organisms are organisms that can NOT that can NOT make their own make their own foodfood

• Heterotrophs Heterotrophs can NOT can NOT directly use the directly use the sun’s energysun’s energy


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ATP – Cellular EnergyATP – Cellular Energy• Adenosine TriphosphateAdenosine Triphosphate• Contains two, high-energy phosphate Contains two, high-energy phosphate

bondsbonds• Also contains the nitrogen base adenine Also contains the nitrogen base adenine

& a ribose sugar& a ribose sugar


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ADPADP• Adenosine DiphosphateAdenosine Diphosphate• ATP releases ATP releases energyenergy, a , a free free

phosphate,phosphate, & & ADPADP when cells take when cells take energy from ATPenergy from ATP

One phosphate bond has been removedcopyright cmassengale

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Importance of ATPImportance of ATP

Principal Compound Used To Store Energy In Living Organisms


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Releasing Energy From ATPReleasing Energy From ATP

• ATP is constantly being ATP is constantly being used and used and remade by cellsremade by cells

• ATP provides all of the energy for ATP provides all of the energy for cell activitiescell activities

• The high energy phosphate bonds The high energy phosphate bonds can be can be BROKENBROKEN to to release energyrelease energy

• The process of releasing ATP’s The process of releasing ATP’s energy & reforming the molecule is energy & reforming the molecule is called called phosphorylationphosphorylation


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More on ATPMore on ATP

• Cells Have Enough ATP To Cells Have Enough ATP To Last For A Last For A Few SecondsFew Seconds

• ATP must ATP must constantlyconstantly be be mademade

• ATP ATP Transfers Energy Very Transfers Energy Very WellWell

• ATP Is ATP Is NOTNOT Good At Energy Good At Energy StorageStorage


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GlucoseGlucose

• Glucose is a Glucose is a monosaccharidemonosaccharide

• CC66HH1212OO66

• One Molecule of glucose One Molecule of glucose Stores Stores 90 Times90 Times More More Chemical Energy Than Chemical Energy Than One Molecule of ATPOne Molecule of ATP


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History of History of Photosynthesis & Photosynthesis &

Plant PigmentsPlant Pigments


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The Photosynthesis The Photosynthesis EquationEquation


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PigmentsPigments

• In addition to water, carbon dioxide, and light energy, photosynthesis requires Pigments

• Chlorophyll is the primary light-absorbing pigment in autotrophs

• Chlorophyll is found inside chloroplasts


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Light and PigmentsLight and Pigments

• Energy From The Sun Enters Earth’s Biosphere As Photons

• Photon = Light Energy Unit

• Light Contains A Mixture Of Wavelengths

• Different Wavelengths Have Different Colors


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Light & PigmentsLight & Pigments

• Different pigmentsDifferent pigments absorb different absorb different wavelengthswavelengths of light of light

• Photons of light Photons of light “excite”“excite” electrons electrons in the plant’s pigmentsin the plant’s pigments

• Excited electrons carry the Excited electrons carry the absorbed energyabsorbed energy

• Excited electrons move to Excited electrons move to HIGHERHIGHER energy levelsenergy levels


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Chlorophyll a and bChlorophyll a and b


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Chlorophyll aChlorophyll a

•Found in all Found in all plants, algae, & plants, algae, & cyanobacteriacyanobacteria

•Makes photosynthesis Makes photosynthesis possiblepossible

•Participates Participates directlydirectly in the in the Light ReactionsLight Reactions

•Can Can accept energyaccept energy from from chlorophyll bchlorophyll b


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Chlorophyll bChlorophyll b• Chlorophyll b is an Chlorophyll b is an

accessory pigmentaccessory pigment• Chlorophyll b acts Chlorophyll b acts indirectlyindirectly

in photosynthesis by in photosynthesis by transferring the light it transferring the light it absorbs to chlorophyll absorbs to chlorophyll aa

• Like chlorophyll a, it Like chlorophyll a, it absorbs red & blue light and absorbs red & blue light and REFLECTS GREENREFLECTS GREEN

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The Biochemical The Biochemical ReactionsReactions

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It Begins with Sunlight!It Begins with Sunlight!


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Photoautotrophs Absorb Light Photoautotrophs Absorb Light EnergyEnergy


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Inside A ChloroplastInside A Chloroplast


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Structure of the ChloroplastStructure of the Chloroplast

• Double membraneDouble membrane organelle organelle• Outer membrane Outer membrane smoothsmooth• Inner membraneInner membrane forms stacks forms stacks

of connected sacs called of connected sacs called thylakoidsthylakoids

• Thylakoid stack is called the Thylakoid stack is called the granungranun (grana-plural) (grana-plural)

• Gel-like material around Gel-like material around grana called grana called stromastroma


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Function of the StromaFunction of the Stroma

• Light IndependentLight Independent reactions occur herereactions occur here

• ATP usedATP used to make to make carbohydrates like carbohydrates like glucoseglucose

• Location of the Location of the Calvin Calvin CycleCycle


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Thylakoid membranesThylakoid membranes

• Light DependentLight Dependent reactions occur reactions occur herehere

• Photosystems are made up of Photosystems are made up of clusters of chlorophyll clusters of chlorophyll moleculesmolecules

• Photosystems are Photosystems are embedded in embedded in the thylakoid membranesthe thylakoid membranes

• The two photosystems are:The two photosystems are: Photosytem IPhotosytem I Photosystem IIPhotosystem II


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Photosynthesis OverviewPhotosynthesis Overview


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Energy CarriersEnergy Carriers

• Nicotinamide Adenine Dinucleotide Nicotinamide Adenine Dinucleotide Phosphate Phosphate (NADP(NADP++))

• NADPNADP+ = + = ReducedReduced Form Form

• Picks Up Picks Up 2 high-energy electrons 2 high-energy electrons and Hand H++ from the Light Reaction to from the Light Reaction to form NADPHform NADPH

• NADPHNADPH carries energy to be carries energy to be passed on to another moleculepassed on to another molecule


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NADPHNADPH


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• Occurs across the Occurs across the thylakoid thylakoid membranesmembranes

• Uses light energyUses light energy

• Produce Produce OxygenOxygen from water from water

• Convert Convert ADP to ATPADP to ATP

• Also convert Also convert NADPNADP++ into the into the energy carrier energy carrier NADPHNADPH

Light Dependent ReactionsLight Dependent Reactions


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Light Dependent ReactionLight Dependent Reaction


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Photosystem IPhotosystem I

•Discovered Discovered FirstFirst

•Active in the final stage of the Active in the final stage of the Light Dependent ReactionLight Dependent Reaction

•Made of 300 molecules of Made of 300 molecules of ChlorophyllChlorophyll

•Almost completely Almost completely chlorophyll achlorophyll a


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Photosystem IIPhotosystem II

•Discovered Discovered SecondSecond

•Active in the beginning stage Active in the beginning stage Of the Light Dependent Of the Light Dependent ReactionReaction

•Contains about Contains about equal equal amounts of chlorophyll a and amounts of chlorophyll a and chlorophyll bchlorophyll b


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Photosynthesis BeginsPhotosynthesis Begins

Photosystem Photosystem II absorbs light energyII absorbs light energy

Electrons are energizedElectrons are energized and passed and passed to the to the Electron Transport ChainElectron Transport Chain

Lost electrons are replaced from the Lost electrons are replaced from the splitting of watersplitting of water into 2H into 2H+, +, free free electrons, and Oxygenelectrons, and Oxygen

2H2H+ + pumped across thylakoid pumped across thylakoid membranemembrane


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Photosystem IPhotosystem I

High-energy electronsHigh-energy electrons are moved are moved to Photosystem I through the to Photosystem I through the Electron Transport ChainElectron Transport Chain

Energy is used to Energy is used to transport Htransport H++ from stroma to inner thylakoid from stroma to inner thylakoid membranemembrane

NADP+ converted to NADPHNADP+ converted to NADPH when it picks up 2 electrons & when it picks up 2 electrons & H+H+


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PhosphorylationPhosphorylation

Enzyme in thylakoid Enzyme in thylakoid membrane called membrane called ATP ATP SynthaseSynthase

As H+ ions passed through As H+ ions passed through thylakoid membrane, thylakoid membrane, enzyme binds them to ADPenzyme binds them to ADP

Forms Forms ATPATP for cellular for cellular


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Light Reaction SummaryLight Reaction Summary

Reactants:Reactants:

• HH22OO

• Light EnergyLight Energy

Energy Products:Energy Products:

• ATPATP

• NADPHNADPHcopyright cmassengale

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Light Independent ReactionLight Independent Reaction

• ATP & NADPHATP & NADPH from light from light reactions used as energyreactions used as energy

• Atmospheric Atmospheric C0C022 is used is used to to

make sugarsmake sugars like glucose and like glucose and fructosefructose

• Six-carbon Sugars made Six-carbon Sugars made during the during the Calvin CycleCalvin Cycle

• Occurs in theOccurs in the stroma stromacopyright cmassengale

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The Calvin CycleThe Calvin Cycle


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The Calvin CycleThe Calvin Cycle

• Two turnsTwo turns of the Calvin Cycle are of the Calvin Cycle are required to make one molecule of required to make one molecule of glucoseglucose

• 3-CO3-CO22 molecules enter the cycle molecules enter the cycle to form several to form several intermediate intermediate compounds (PGA)compounds (PGA)

• A 3-carbon molecule called A 3-carbon molecule called Ribulose BiphosphateRibulose Biphosphate (RuBP) is (RuBP) is used to regenerate the Calvin used to regenerate the Calvin cyclecycle


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Factors Affecting the Rate of Factors Affecting the Rate of PhotosynthesisPhotosynthesis

• Amount of Amount of available wateravailable water

• TemperatureTemperature

• Amount of Amount of available light available light energyenergy


1 photosynthesis energy & life. 2 overview of photosynthesis copyright cmassengale

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