AP Biology Day 21 Friday, October 7, 2016

Do-NowGroup Discussion

•  In your groups, discuss the 2014 FRQ prompt • Discuss possible answers for each part

• Jot down your ideas as a group to help plan a response

• Revise your explanations until you have the BEST possible answer

Announcements•  Clearmissingassignments!

•  StudyforCh.10quiz&Ch.9-10testJ• Quarter1ends10/14à

• Retakes/missingworkbyTuesday

CW/HW Assignments 7.  Ch. 9 Practice FRQ 8.  Ch. 10 Lecture Notes 9.  Ch. 10 VCN

1.  Labs and logs MUST be turned in 2.  Ch. 10 Video CN (1 video) 3.  Study Ch. 9-10 4.  Lab next Friday

PLANNER

EssenJalknowledgestandards• 2.A.1: All living systems require constant input of free energy

• 2.A.2: Organisms capture and store free energy for use in biological processes

FLT•  I will be able to:

•  describe the structure of a chloroplast

• describe the the role of ATP and NADPH in the Calvin Cycle

•  compare and contrast oxidative phosphorylation and photophosphorylation in chloroplasts

•  By completing Ch. 10 Lecture Notes

Ch.10:Photosynthesis

Energy=Life•  Alllivingorganismsmustobtainenergyinordertolive

•  Autotrophs=Producetheirownenergyviaphotosynthesisorchemosynthesis

•  Heterotrophs=consumeotherorganisms

Ø Theycapturefreeenergypresentincarboncompoundsproducedbyotherorganisms

Energy=Life•  AutotrophsmaketheirownfoodandsustainthemselveswithouteaJnganythingderivedfromotherorganisms

•  Autotrophsaretheproducersofthebiosphere,producingorganicmolecules(suchasglucose)fromCO2andotherinorganicmolecules

•  Almostallplantsarephotoautotrophs,usingtheenergyofsunlighttomakeorganicmoleculesfromwaterandcarbondioxide

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Autotrophs = Producers

(a) Plants

(c) Unicellular protist 10 µm

1.5 µm

40 µm (d) Cyanobacteria

(e) Purple sulfur bacteria

(b) Multicellular alga

Review•  Livingcellsrequireenergyfromoutsidesources

•  Energyflowsintoanecosystemassunlightandleavesasheat

•  PhotosynthesisgeneratesO2andorganicCHOmolecules(usedincellularrespiraJon)

Energy Flow and Chemical Recycling in Ecosystems

IN: Light Energy

ECOSYSTEM

Photosynthesis in chloroplasts

CO2 + H2O

Cellular respiration in mitochondria

Organic Molecules + O2

ATP powers most cellular work

OUT: Heat energy

ATP

Chloroplasts•  Photosynthesistypicallyoccursinleaves•  Chlorophyll,apigmentfoundinchloroplasts,givesthemtheirgreenappearance

•  ChlorophyllabsorbsvisiblelightE,whichisusedtosynthesizeorganicmoleculessuchasglucose

•  CO2entersandO2exitstheleafthroughmicroscopicporescalledstomata

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ChloroplastStructure

ChloroplastStructure•  Intermembranespaceb/tinnerandoutermembranes

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ChloroplastStructure•  Thylakoid=flaZened,membranoussacs

•  Grana=stacksofthylakoids

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ChloroplastStructure•  Stroma=densefluidinthechloroplast

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ChloroplastStructure

Chloroplast•  Chloroplastsprobablyevolvedfromcyanobacteria(photosyntheDcbacteria)

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Chloroplast•  Chloroplastsarefoundmainlyincellsofthemesophyll(interiorDssueoftheleaf)

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Chloroplast•  Atypicalmesophyllcellhas30-40chloroplasts

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Zooming in on the location of photosynthesi

s in a plant

5 µm

Mesophyll cell

Stomata CO2 O2

Chloroplast

Mesophyll

Vein

Leaf cross section

Pair-Share-Respond1.   Whatarephotoautotrophs?

2.   Describethemainstructuresofthechloroplast

3.   Whatisthesignificanceofastomata?

4.   Whatarecyanobacteria?

RespiraJonReview•  Recall:

•  6O2+C6H12O6à6CO2+6H2O+Energy

•  Thisoccursinthreemainsteps:

• Glycolysis• Krebs/CACycle•  ETC

•  Wheredoestheglucosecomefrom??

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PhotosynthesisOverview•  Photosynthesis=energytransferprocessthatconvertssolarenergyintostoredchemicalenergy

•  PhotosynthesisprovidestheEarthwithfoodandatmosphericoxygen

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PhotosynthesisOverview•  Photosynthesis can be summarized with the

following equation 6CO2 + 6H2O + Light E è C6H12O6 + 6O2

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Recall

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PhotosynthesisOverview•  PhotosynthesisisaredoxreacJon:

•  H2OisoxidizedtoO2

•  CO2isreducedtoC6H12O6

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StagesofPhotosynthesis1.  ThelightdependentreacJons2.  ThelightindependentreacJons(CalvinCycle)

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Stages1.   The light dependent reactions

•  Occur within and across the thylakoid membrane

•  H2O is split into hydrogen and oxygen (photolysis)

•  The e-s hold the free energy from the light

•  Through an ETC, light E is transformed into ATP and NADPH

•  Generate ATP by photophosphorylation

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Stages2.   The light independent reactions (Calvin Cycle)

•  Takes place in the stroma

•  Forms C6H12O6 from CO2 using ATP and NADPH

•  The Calvin Cycle begins with carbon fixation, which incorporates CO2 into organic molecules and then reduction produces sugar

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Light

Fig. 10-5-1

H2O

Chloroplast

Light Reactions

NADP+

P ADP

i +

Light

Light Reactions H2O

Chloroplast

Light Reactions

NADP+

P ADP

i +

ATP

NADPH

O2

Light

H2O

Chloroplast

Light Reactions

NADP+

P ADP

i +

ATP

NADPH

O2

Calvin Cycle

CO2

Light

Photosynthesis H2O

Chloroplast

Light Reactions

NADP+

P ADP

i+

ATP

NADPH

O2

Calvin Cycle

CO2

[CH2O] (sugar)

Pair-Share-Respond1.   Definephotosynthesis2.   Whyisphotosynthesisconsideredto

bearedoxreacDon?Bespecific

3.   Whatarethetwostagesofphotosynthesisandwheredotheytakeplace?

4.   IdenDfytwothingsthatoccurinthefirststage.

TheNatureofSunlight•  LightisaformofelectromagneJcenergy,alsocalled

electromagneJcradiaJon

•  LikeotherelectromagneJcenergy,lighttravelsinrhythmicwaves

•  Wavelengthisthedistancebetweencrestsofwaves

•  WavelengthdeterminesthetypeofelectromagneJcenergy

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TheNatureofSunlight•  TheelectromagneDcspectrum=theenDrerangeof

electromagneDcenergy,orradiaDon

•  Visiblelightconsistsofwavelengths(includingthosethatdrivephotosynthesis)thatproducecolorswecansee

•  LightalsobehavesasthoughitconsistsofdiscreteenergyparJcles,calledphotons

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UV

Visible light

Infrared Micro- waves

Radio waves X-rays Gamma

rays

103 m 1 m

(109 nm) 106 nm 103 nm 1 nm 10–3 nm 10–5 nm

380 450 500 550 600 650 700 750 nm

Longer wavelength Lower energy Higher energy

Shorter wavelength

Electromagnetic Spectrum

PhotosyntheJcPigments:LightReceptors•  Pigments=substancesthatabsorbvisiblelight

•  Differentpigmentsabsorbdifferentwavelengths

•  WavelengthsthatarenotabsorbedarereflectedortransmiZed

•  Leavesappeargreenbecausechlorophyllreflectsgreenlight.Weseereflectedlight.

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Why leaves are green: interaction of light with chloroplasts

Reflected light

Absorbed light

Light

Chloroplast

Transmitted light

Granum

Spectrophotometer•  Spectrophotometer=measuresapigment’sabilitytoabsorb

variouswavelengths

•  ThismachinesendslightthroughpigmentsandmeasuresthefracJonoflighttransmiZedateachwavelength

•  TransmiZedlightislightthatisnotabsorbed

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Determining an absorption spectrum

Galvanometer

Slit moves to pass light of selected wavelength

White light

Green light

Blue light

The low transmittance (high absorption) reading indicates that chlorophyll absorbs most blue light.

The high transmittance (low absorption) reading indicates that chlorophyll absorbs very little green light.

Refracting prism

Photoelectric tube

Chlorophyll solution

TECHNIQUE

1 2 3

4

AbsorpJonSpectrum•  Absorption spectrum = a graph plotting a

pigment’s light absorption vs. wavelength •  Spectrum of chlorophyll a shows that violet-blue

and red light work best for photosynthesis

•  An action spectrum profiles the relative effectiveness of different wavelengths of radiation in driving a process such as photosynthesis

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Wavelength of light (nm)

Action spectrum

Absorption spectra

Engelmann�s experiment

Aerobic bacteria

RESULTS

Rat

e of

pho

tosy

nthe

sis

(mea

sure

d by

O2 r

elea

se)

Abs

orpt

ion

of li

ght b

y ch

loro

plas

t pig

men

ts

Filament of alga

Chloro- phyll a Chlorophyll b

Carotenoids

500 400 600 700

700 600 500 400

•  ChlorophyllaisthemainphotosyntheDcpigment

•  Itabsorbsthelightenergy•  Accessorypigments,suchaschlorophyllb,broadenthe

spectrumusedforphotosynthesis

•  Accessorypigmentscalledcarotenoidsabsorbexcessivelightthatwoulddamagechlorophyll

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Chlorophyll

Porphyrin ring: light-absorbing �head� of molecule; note magnesium atom at center

in chlorophyll a CH3

Hydrocarbon tail: interacts with hydrophobic regions of proteins inside thylakoid membranes of chloroplasts; H atoms not shown

CHO in chlorophyll b

Chlorophyll•  Energyfromphotonsmaybeabsorbedbyelectrons

•  Whenapigmentabsorbslight,itgoesfromagroupstatetoanexcitedstate,whichisunstable

•  Whenexcitede-sreturntothegroundstate,photonsaregivenoff,anaUerglowcalledfluorescence

•  Ifilluminated,anisolatedsoluJonofchlorophyllwillfluoresce,givingofflightandheat

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Chlorophyll

Porphyrin ring: light-absorbing �head� of molecule; note magnesium atom at center

in chlorophyll a CH3

Hydrocarbon tail: interacts with hydrophobic regions of proteins inside thylakoid membranes of chloroplasts; H atoms not shown

CHO in chlorophyll b

Excitation of isolated chlorophyll by light

(a) Excitation of isolated chlorophyll molecule

Heat

Excited state

(b) Fluorescence

Photon Ground state

Photon (fluorescence)

Ener

gy o

f ele

ctro

n

e–

Chlorophyll molecule

CW

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