PowerLecture: Chapter 7 Where It Starts - Photosynthesis.

PowerLecture:PowerLecture:Chapter 7Chapter 7

Where It Starts - PhotosynthesisWhere It Starts - Photosynthesis

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Section 7.0 : ASU Center for the Study of Early Events in Photosynthesis

Section 7.0 : When Did Photosynthesis Emerge on Earth?

David Des Marais, Science, Sept. 8, 2000.

How Would You Vote?How Would You Vote?The following is the question for this chapter. See The following is the question for this chapter. See

the "Polls and ArtJoinIn" for this chapter if your the "Polls and ArtJoinIn" for this chapter if your campus uses a Personal Response System,or campus uses a Personal Response System,or have your students vote online. See national have your students vote online. See national results below.results below.

Should public funds be used to find potentiShould public funds be used to find potentially life supporting planets too far away for ally life supporting planets too far away for us to visit?us to visit?

Plants are Plants are autotrophsautotrophs, or self-nourishing organisms, or self-nourishing organisms

The first autotrophs filled Earth’s atmosphere with oxygen, creating The first autotrophs filled Earth’s atmosphere with oxygen, creating an ozone (Oan ozone (O33) layer) layer

The ozone layer became a shield against deadly UV rays from the The ozone layer became a shield against deadly UV rays from the sun, allowing life to move out of the oceansun, allowing life to move out of the ocean

Impacts, Issues: Impacts, Issues: Sunlight and Sunlight and SurvivalSurvival

Fig. 7-1, p.106

Sunlight and SurvivalSunlight and Survival

p.107

Sunlight and SurvivalSunlight and Survival

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Section 7.1: Chemistry of Autumn Colors

Section 7.1: Molecule of the Month—Chlorophyll

Section 7.1: Foliage Afire: Why Leaves Change Colors. Esther McGuire. New York State Conservationist, Oct. 1998.

Section 7.1: Photochemistry of Chlorophyll. Bulletin of the South Carolina Academy of Science, 2002.

Electromagnetic Spectrum Electromagnetic Spectrum

Shortest Shortest Gamma raysGamma rays

wavelength wavelength X-raysX-rays

UV radiationUV radiation

Visible lightVisible light

Infrared radiationInfrared radiation

MicrowavesMicrowaves

LongestLongest Radio wavesRadio waves

wavelengthwavelength

PhotonsPhotons

Packets of light energyPackets of light energy

Each type of photon has fixed amount of Each type of photon has fixed amount of energyenergy

Photons having most energy travel as Photons having most energy travel as shortest wavelength (blue-violet light)shortest wavelength (blue-violet light)

Visible Light Visible Light

Wavelengths humans perceive as different Wavelengths humans perceive as different colorscolors

Violet (380 nm) to red (750 nm) Violet (380 nm) to red (750 nm) Longer wavelengths, lower energyLonger wavelengths, lower energy

Figure 7-28

shortest wavelengths

(most energetic)

range of most radiationreaching Earth’s surface

gamma rays

range of heat escapingfrom Earth’s surface

longest wavelengths

(lowest energy)x

raysultravioletradiation

near-infraredradiation

infraredradiation microwaves radio

waves

VISIBLE LIGHT

Wavelengths of light (nanometers)

Fig. 7-2, p.108


400 450 500 550 600 650 700


Wavelengths of light

PigmentsPigments

Color you see is the wavelengths not Color you see is the wavelengths not absorbed absorbed

Light-catching part of molecule often has Light-catching part of molecule often has alternating single and double bondsalternating single and double bonds

These bonds contain electrons that are These bonds contain electrons that are capable of being moved to higher energy capable of being moved to higher energy levels by absorbing light levels by absorbing light

Variety of Pigments Variety of Pigments

Chlorophylls Chlorophylls aa and and bb

CarotenoidsCarotenoids

AnthocyaninsAnthocyanins

PhycobilinsPhycobilins

ChlorophyllsChlorophyllsW

avel

eng

th a

bso

rpti

on

(%

)

Wavelength (nanometers)

chlorophyll b

chlorophyll a

Main pigments in most photoautotrophsMain pigments in most photoautotrophs

Accessory PigmentsAccessory Pigmentsp

erce

nt

of

wav

elen

gth

s ab

sorb

ed

wavelengths (nanometers)

beta-carotenephycoerythrin (a phycobilin)

Carotenoids, Phycobilins, Anthocyanins

Fig. 7-3a, p.109

PigmentsPigments

Fig. 7-3b, p.109

PigmentsPigments

Fig. 7-3c, p.109

PigmentsPigments

Fig. 7-3d, p.109

PigmentsPigments

Fig. 7-3e, p.109

PigmentsPigments

Pigments in PhotosynthesisPigments in Photosynthesis

BacteriaBacteria Pigments in plasma membranesPigments in plasma membranes

PlantsPlants Pigments and proteins organized into Pigments and proteins organized into

photosystems that are embedded in thylakoid photosystems that are embedded in thylakoid membrane systemmembrane system



Section 7.2: Milestones in Photosynthesis Research

Section 7.2: Photosynthetic Pigments in Bacteria and Plants

Section 7.2: Sunlight at Southall Green. Norman & Elaine Beale. Perspectives in Biology and Medicine, Summer 2001.

Section 7.2: Photosynthesis and Respiration in a Jar. Joseph Buttner. Science Activities, Summer 2000.

T.E. Englemann’s Experiment T.E. Englemann’s Experiment

Background Background Certain bacterial cells will move Certain bacterial cells will move

toward places where oxygen concentration toward places where oxygen concentration is highis high

Photosynthesis produces oxygenPhotosynthesis produces oxygen

T.E. Englemann’s ExperimentT.E. Englemann’s Experiment

Fig. 7-4a, p.110


Fig. 7-4c, p.110


Fig. 7-5, p.110


Englemann’s Experiment


Linked ProcessesLinked Processes

PhotosynthesisPhotosynthesis

Energy-storing Energy-storing pathway pathway

Releases oxygenReleases oxygen

Requires carbon Requires carbon dioxidedioxide

Aerobic RespirationAerobic Respiration

Energy-releasing Energy-releasing pathwaypathway

Requires oxygenRequires oxygen

Releases carbon Releases carbon dioxidedioxide



Section 7.3: MIT Biology Hypertextbook—Physics of Photosynthesis

Chloroplast StructureChloroplast Structure

two outer membranes

inner membrane system(thylakoids connected by channels)

stroma

Fig. 7-6, p.111

Photosynthesis EquationPhotosynthesis Equation

12H2O + 6CO2 6O2 + C2H12O6 + 6H2O

Water Carbon Dioxide

Oxygen Glucose Water

LIGHT ENERGY

In-text figurePage 111

Fig. 7-6a, p.111


(see next slide)

leaf’s upper epidermis photosynthetic cells

Fig. 7-6a, p.111

vein stoma (gap) across lower leaf epidermis


stroma

thylakoid compartment

thylakoid membrane system inside stroma

Fig. 7-6b, p.111

two outer membranes


CO2H2O

SUNLIGHT

Fig. 7-6c, p.111

O2

light-dependant reactions

light-independant

reactions

sugars

CHLOROPLAST

NADPH, ATP

NADP+, ADP


Sites of Photosynthesis

Photosynthesis EquationPhotosynthesis Equation

Where Atoms End UpWhere Atoms End Up

Products 6O2 C6H12O6 6H2O

Reactants 12H2O 6CO2

Two Stages of PhotosynthesisTwo Stages of Photosynthesis

sunlight water uptake carbon dioxide uptake

ATP

ADP + Pi

NADPH

NADP+

glucoseP

oxygen release

LIGHT-INDEPENDENT

REACTIONS

LIGHT-DEPENDENT REACTIONS

new water

Arrangement of PhotosystemsArrangement of Photosystems

water-splitting complex thylakoidcompartment

H2O 2H + 1/2O2

P680

acceptor

P700

acceptor

pool of electron carriers stromaPHOTOSYSTEM II

PHOTOSYSTEM I

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Section 7.4: Photosynthetic Antennas and Reaction Centers

Section 7.4: The Amazing All-Natural Light Machine (light-harvesting molecule LH2). Mark Caldwell.

scover, Dec. 1995.

Pigments absorb light energy, give up ePigments absorb light energy, give up e--, , which enter electron transfer chainswhich enter electron transfer chains

Water molecules split, ATP and NADH Water molecules split, ATP and NADH form, and oxygen is releasedform, and oxygen is released

Pigments that gave up electrons get Pigments that gave up electrons get replacementsreplacements

Light-Dependent ReactionsLight-Dependent Reactions

Fig. 7-7, p.112

photon

Light-Harvesting Complex

Photosystem


Noncyclic pathway of electron flow


NADPH

NADP + + H+

thylakoidcompartment

thylakoidmembrane

stroma

ATPADP + Pi

H+

H+

H+H+

H+

H+

H+

H+ H+

H+

H+

PHOTOSYSTEM IsunlightPHOTOSYSTEM II

LIGHT-HARVESTING

COMPLEX

Fig. 7-8, p.113

H+

e- e-e- e-e- e-

H+

e-

O2

H2O

cross-section through a disk-shaped fold in the

thylakoid membrane

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Photosystem Function: Photosystem Function: Harvester Pigments Harvester Pigments

Most pigments in photosystem are Most pigments in photosystem are harvester pigmentsharvester pigments

When excited by light energy, these When excited by light energy, these pigments transfer energy to adjacent pigments transfer energy to adjacent pigment moleculespigment molecules

Each transfer involves energy loss Each transfer involves energy loss

Pigments in a PhotosystemPigments in a Photosystem

reaction center

Photosystem Function: Photosystem Function: Reaction Center Reaction Center

Energy is reduced to level that can be Energy is reduced to level that can be captured by molecule of chlorophyll captured by molecule of chlorophyll aa

This molecule (P700 or P680) is the This molecule (P700 or P680) is the reaction center of a photosystemreaction center of a photosystem

Reaction center accepts energy and Reaction center accepts energy and donates electron to acceptor molecule donates electron to acceptor molecule

Harvesting photo energy

Photo EnergyPhoto Energy

Electron Transfer ChainElectron Transfer Chain

Adjacent to photosystem Adjacent to photosystem Acceptor molecule donates electrons from Acceptor molecule donates electrons from

reaction centerreaction center

As electrons pass along chain, energy As electrons pass along chain, energy they release is used to produce ATP they release is used to produce ATP

Cyclic Electron FlowCyclic Electron Flow

Electrons Electrons are donated by P700 in photosystem I to are donated by P700 in photosystem I to

acceptor moleculeacceptor molecule flow through electron transfer chain and back flow through electron transfer chain and back

to P700to P700

Electron flow drives ATP formationElectron flow drives ATP formation No NADPH is formedNo NADPH is formed

Cyclic Electron FlowCyclic Electron Flow

electron acceptor

electron transfer chain

e–

e–

e–

e–

ATP

Electron flow through transfer chain sets up

conditions for ATP formation at other membrane sites.

Noncyclic Electron FlowNoncyclic Electron Flow

Two-step pathway for light absorption and Two-step pathway for light absorption and

electron excitationelectron excitation

Uses two photosystems: type I and Uses two photosystems: type I and

type II type II

Produces ATP and NADPHProduces ATP and NADPH

Involves photolysis - splitting of waterInvolves photolysis - splitting of water

Machinery of Machinery of Noncyclic Electron FlowNoncyclic Electron Flow

photolysis

H2O

NADP+ NADPH

e–

ATP

ATP SYNTHASE

PHOTOSYSTEM IPHOTOSYSTEM II ADP + Pi

e–

first electron transfer chain

second electron transfer chain

Energy ChangesEnergy ChangesP

ote

nti

al t

o t

ran

sfer

en

erg

y (v

olt

s)

H2O 1/2O2 + 2H+

(Photosystem II)

(Photosystem I)

e– e–

e–e–

secondtransfer

chain

NADPHfirst

transferchain

PHOTOSYSTEM I

p700*

photon e-

H+

Cyclic Pathway of ATP Formation

Hig

her

en

erg

y p700

Fig. 7-9a, p.114

PHOTOSYSTEM I

e-

Noncyclic Pathway of ATP and NADPH Formation

2H2O

NADPH

NADH+

p700*

p700photon

PHOTOSYSTEM II

p680*

p680

4H+ + O2

Fig. 7-9b, p.114

Energy changes in photosynthesis.

Energy ChangesEnergy Changes

Chemiosmotic Model Chemiosmotic Model of ATP Formationof ATP Formation

Electrical and HElectrical and H++ concentration gradients concentration gradients are created between thylakoid are created between thylakoid compartment and stromacompartment and stroma

HH++ flows down gradients into stroma flows down gradients into stroma through ATP synthesisthrough ATP synthesis

Flow of ions drives formation of ATPFlow of ions drives formation of ATP

Chemiosmotic Model for ATP Chemiosmotic Model for ATP FormationFormation

ADP + Pi

ATP SYNTHASE

Gradients propel H+ through ATP synthases;ATP forms by phosphate-group transfer

ATP

H+ is shunted across membrane by some components of the first electron transfer chain

PHOTOSYSTEM II

H2Oe–

acceptor

Photolysis in the thylakoid compartment splits water



Section 7.6: 1961 Nobel Prize—Melvin Calvin

Section 7.6: Biographical Memoirs—Melvin Calvin

Section 7.6: Robust Plants' Secret? Rubisco Activase! Marcia Wood. Agricultural Research, Nov. 2002.

Section 7.6: Revealing the Secrets of Old Sol's Sugar Factories. Wim Vermaas. World and I, Mar. 1998.

Synthesis part of Synthesis part of

photosynthesisphotosynthesis

Can proceed in the darkCan proceed in the dark

Take place in the stromaTake place in the stroma

Calvin-Benson cycleCalvin-Benson cycle

Light-Independent ReactionsLight-Independent Reactions

Calvin-Benson Cycle Calvin-Benson Cycle

Overall reactantsOverall reactants Carbon dioxideCarbon dioxide

ATPATP

NADPHNADPH

Overall productsOverall products GlucoseGlucose

ADPADP

NADPNADP++

Reaction pathway is cyclic and RuBP (ribulose bisphosphate) is regenerated

Calvin- Calvin- Benson Cycle Benson Cycle

CARBON FIXATION

6 CO2 (from the air)

6 6RuBP

PGA

unstable intermediate

6 ADP

6

12

12ATP

ATP

NADPH

10

12PGAL

glucoseP

PGAL2

Pi

12 ADP12 Pi

12 NADP+

12

4 Pi

PGAL

Fig. 7-10a, p.115

THESE REACTIONS PROCEED IN THE CHLOROPLAST’S

STROMA

Calvin- Benson Cycle Calvin- Benson Cycle

ATP

6 RuBP

phosphorylated glucose

10 PGAL

1 Pi

12 PGA

Calvin-Benson cycle

Fig. 7-10b, p.115

6 ADP

ATP

12 ADP +12 Pi

6CO2

NADPH

12 NADP+

12 PGAL

4 Pi

1

12

12

Calvin- Calvin- Benson Benson

Cycle Cycle

Calvin-Benson cycle

Calvin- Benson Cycle Calvin- Benson Cycle



Section 7.7: Botany Online: Photosynthesis—C3, C4, and CAM

Section 7.7: International Society of Crassulacean Acid Metabolism Research

Section 7.7: CAM Photosynthesis: Not Just for Desert Plants. Elia Ben-Ari. BioScience, Dec. 1998.

Section 7.7: Evolution of CAM and C4 Carbon-Concentrating Mechanisms. Jon Keeley et al. International Journal of Plant Sciences, May 2003.

In Calvin-Benson cycle, the first stable In Calvin-Benson cycle, the first stable intermediate is a three-carbon PGAintermediate is a three-carbon PGA

Because the first intermediate has three Because the first intermediate has three carbons, the pathway is called the C3 carbons, the pathway is called the C3 pathwaypathway

The C3 PathwayThe C3 Pathway

Photorespiration in C3 PlantsPhotorespiration in C3 Plants

On hot, dry days stomata closeOn hot, dry days stomata close Inside leaf Inside leaf

Oxygen levels riseOxygen levels rise Carbon dioxide levels dropCarbon dioxide levels drop

Rubisco attaches RuBP to oxygen instead Rubisco attaches RuBP to oxygen instead of carbon dioxideof carbon dioxide

Only one PGAL forms instead of twoOnly one PGAL forms instead of two

Fig. 7-11a1, p.116

C3 PlantsC3 Plants

upperepidermis

palisademesophyll

spongymesophyll

lowerepidermis

stoma leaf vein air space

Basswood leaf, cross-section.

Fig. 7-11a2, p.116

C3 PlantsC3 Plants

6 PGA + 6 glycolate

6 PGAL

1 PGAL

Twelve turns of the cycle, not just six, to make one 6-carbon sugar

RuBP

Calvin-Benson Cycle

CO2

+ water

5 PGAL

Stomata closed: CO2 can’t get in; O2 can’t get out

Rubisco fixes oxygen, not carbon, in mesophyll cells in leaf

Fig. 7-11a3, p.117

C3 PlantsC3 Plants

C4 Plants C4 Plants

Carbon dioxide is fixed twiceCarbon dioxide is fixed twice In mesophyll cells, carbon dioxide is fixed to In mesophyll cells, carbon dioxide is fixed to

form four-carbon oxaloacetate form four-carbon oxaloacetate

Oxaloacetate is transferred to bundle-sheath Oxaloacetate is transferred to bundle-sheath

cellscells

Carbon dioxide is released and fixed again in Carbon dioxide is released and fixed again in


Fig. 7-11b1, p.117

C4 PlantsC4 Plants

upperepidermis

mesophyllcell

bundle-sheath cell

lowerepidermis

Basswood leaf, cross-section.

Fig. 7-11b2, p.117

C4 PlantsC4 Plants

oxaloacetate

malateC4

cycle

pyruvate

CO2

12 PGAL

10 PGAL

2 PGAL

1 sugar

RuBP Calvin-Benson

Cycle

Carbon fixed in the mesophyll cell, malate diffuses into adjacent bundle-sheath cell

In bundle-sheath cell, malate gets converted to pyruvate with release of CO2,

which enters Calvin-Benson cycle

12 PGAL

PEP

Stomata closed: CO2 can’t get in; O2 can’t get out

Fig. 7-11b3, p.117

C4 C4 PlantsPlants

CAM PlantsCAM Plants

Carbon is fixed twice (in same cells)Carbon is fixed twice (in same cells) Night Night

Carbon dioxide is fixed to form organic acidsCarbon dioxide is fixed to form organic acids

DayDay Carbon dioxide is released and fixed in Carbon dioxide is released and fixed in


Fig. 7-11c1, p.117


Fig. 7-11c2, p.117

epidermis with thick cuticle

mesophyll cell

air space

stoma

CAM CAM PlantsPlants

Stomata stay closed during day, open for CO2 uptake at night only.

C4 CYCLE

Calvin-Benson

Cycle

C4 cycle operates at night when CO2 from aerobic respiration fixed

1 sugar

CO2 that accumulated overnight used in C3 cycle during the day

Fig. 7-11c3, p.117


C3-C4 comparison


Summary of PhotosynthesisSummary of Photosynthesis

Figure 7-14Page 120

light6O2

12H2O

CALVIN-BENSON CYCLE

C6H12O6

(phosphorylated glucose)

NADPHNADP+ATPADP + Pi

PGA PGAL

RuBP

P

6CO2

end product (e.g., sucrose, starch, cellulose)

LIGHT-DEPENDENT REACTIONS

6H2O

LIGHT-INDEPENDENT REACTIONS

Summary of PhotosynthesisSummary of Photosynthesis

Photosynthesis overview



Section 7.8: NASA’s Earth Observatory—Phytoplankton

Section 7.8: The Plankton Net

Section 7.8: A Model of Phytoplankton Blooms. Amit Huppert et al. The American Naturalist, Feb. 2002.

Section 7.8: Rust in the Wind (absence of phytoplankton in the ocean). Mary Beth Aberlin. The Sciences, March–April 1996.

Videos: CNNVideos: CNN

Ask your Thomson Sales Representative for Ask your Thomson Sales Representative for these volumes on CD or VHSthese volumes on CD or VHS

Biology, 2002, Vol. 6, Biology, 2002, Vol. 6, Algal FuelAlgal Fuel (2:00) (2:00)

PhotoautotrophsPhotoautotrophs

Carbon source is carbon dioxideCarbon source is carbon dioxide

Energy source is sunlightEnergy source is sunlight

HeterotrophsHeterotrophs

Get carbon and energy by eating autotrophs or one Get carbon and energy by eating autotrophs or one

anotheranother

Carbon and Energy SourcesCarbon and Energy Sources

Fig. 7-12, p.118

sunlight energy

Photosynthesis1. H2O is split by light energy. Its oxygen diffuses away; its electrons, hydrogen enter transfer chains with roles in ATP formation. Coenzymes pick up the electrons and hydrogen

2. ATP energy drives the synthesis of glucose from hydrogen and electrons (delivered by coenzymes), plus carbon and oxygen (from carbon dioxide).

glucose (stored energy, building blocks)

carbon dioxide,

water

oxygen

Aerobic Respiration1. Glucose is broken down completely to carbon dioxide and water. Coenzymes pick up the electrons, hydrogens.

2. The coenzymes give up the electrons and hydrogen atoms to oxygen-requiring transfer chains that have roles in forming many ATP molecules.

ATP available to drive nearly all cellular tasks

Carbon and Energy SourcesCarbon and Energy Sources

Photoautotrophs Photoautotrophs

Capture sunlight energy and use it to carry Capture sunlight energy and use it to carry out photosynthesisout photosynthesis

PlantsPlants

Some bacteriaSome bacteria

Many protistansMany protistans

NORTH AMERICA ATLANTIC OCEAN

AFRICA

SPAINWinter

Spring

Fig. 7-13, p.119

Photoautotrophs Photoautotrophs

Satellite Images Show Satellite Images Show PhotosynthesisPhotosynthesis

Photosynthetic activity in spring

Atlantic Ocean

Figure 7-13Page 119

p.120

12H2O + 6CO2 6O2 + C2H12O6 + 6H2O

Water Carbon Dioxide

Oxygen Glucose Water

light energy

enzymes

sunlight

Calvin-Benson

cycle

Light-DependentReactions

end products (e.g., sucrose, starch, cellulose)

ATP

12 PGAL

Light-Independent

Reactions

phosphorylated glucose

6H2O

6 RuBP

12H2O 6O2

NADPH NADP+

6CO2

ADP + Pi

Fig. 7-14, p.120

Fig. 7-15, p.121

Fig. 7-16a, p.121

Fig. 7-16b, p.121

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