Slide 1

Chapter 10:Chapter 10:

PhotosynthesisPhotosynthesis

Figure 10.2

(a) Plants(b) Multicellular

alga

(c) Unicellularprotists

(d) Cyanobacteria

(e) Purple sulfurbacteria

10 m

1 m

40 m

Slide 3

What we What we (should) already (should) already

know!know!

Sunlight energy

ECOSYSTEM

Photosynthesisin chloroplasts

GlucoseCO2

O2H2O

Cellular respirationin mitochondria

(for cellular work)

Heat energy

ATP

Slide 4

Plants are producersPlants are producers

• Autotrophs – make their own organic Autotrophs – make their own organic molecules from inorganic carbon (COmolecules from inorganic carbon (CO22))

• Photoautotrophs – use light to Photoautotrophs – use light to make organic moleculesmake organic molecules

• Heterotrophs - obtain organic molecules Heterotrophs - obtain organic molecules from another organismfrom another organism

• ConsumersConsumers

• DecomposersDecomposers

Figure 10.4a

Mesophyll

Leaf cross section

Chloroplasts Vein

Stomata

Chloroplast Mesophyllcell

CO2 O2

20 m

Leaf Leaf StructurStructur

ee

Figure 10.4b

Outermembrane

IntermembranespaceInnermembrane

1 m

Thylakoidspace

ThylakoidGranumStroma

Chloroplast

ChloroplasChloroplaststs

Figure 10.5

Reactants:

Products:

6 CO2

6 H2O 6 O2

12 H2O

C6H12O6

PhotosynthesisPhotosynthesis

Slide 8

Tracer ExperimentTracer Experiment

• Used radiolabeled oxygen atoms in the reactants Used radiolabeled oxygen atoms in the reactants to determine which contributed the O2 that is to determine which contributed the O2 that is released by plantsreleased by plants

• Could be from COCould be from CO22 or H or H22OO

Slide 9

Oxidation-Reduction Reactions Oxidation-Reduction Reactions (Redox)(Redox)• Occurs when electrons are moved from one Occurs when electrons are moved from one

molecule to anothermolecule to another

• The molecule that loses the The molecule that loses the electron(s) is OXIDIZED (called electron(s) is OXIDIZED (called oxidation)oxidation)

• The molecule that gains the The molecule that gains the electron(s) is REDUCED (called electron(s) is REDUCED (called reductions)reductions)

• They will always go togetherThey will always go together

• As electrons move, they gain potential As electrons move, they gain potential energy (in photosynthesis)energy (in photosynthesis)

• In photosynthesis, electrons move from In photosynthesis, electrons move from water to CO2, forming sugarswater to CO2, forming sugars

Figure 10.UN01

Energy 6 CO2 6 H2OC6 H12 O6 6 O2

becomes reduced

becomes oxidized

Photosynthesis is a Redox Photosynthesis is a Redox ReactionReaction

Figure 10.6-1

Light

LightReactions

Chloroplast

NADP

ADP

+ P i

H2O

Figure 10.6-2

Light

LightReactions

Chloroplast

ATP

NADPH

NADP

ADP

+ P i

H2O

O2

Figure 10.6-3

Light

LightReactions

CalvinCycle

Chloroplast

ATP

NADPH

NADP

ADP

+ P i

H2O CO2

O2

Figure 10.6-4

Light

LightReactions

CalvinCycle

Chloroplast

[CH2O](sugar)

ATP

NADPH

NADP

ADP

+ P i

H2O CO2

O2

Figure 10.7

Gammarays X-rays UV Infrared

Micro-waves

Radiowaves

Visible light

Shorter wavelength Longer wavelength

Lower energyHigher energy

380 450 500 550 600 650 700 750 nm

105 nm 103 nm 1 nm 103 nm 106 nm (109 nm) 103 m1 m

Ele

ctro

magneti

c Ele

ctro

magneti

c Spect

rum

Spect

rum

Figure 10.8

Chloroplast

LightReflectedlight

Absorbedlight

Transmittedlight

Granum

Chloroplasts absorb only certain Chloroplasts absorb only certain colorscolors

Figure 10.9

Whitelight

Refractingprism

Chlorophyllsolution

Photoelectrictube

Galvanometer

Slit moves topass lightof selectedwavelength.

Greenlight

High transmittance(low absorption):Chlorophyll absorbsvery little green light.

Bluelight

Low transmittance(high absorption):Chlorophyll absorbsmost blue light.

TECHNIQUE

Figure 10.10

(b) Action spectrum

(a) Absorptionspectra

Engelmann’sexperiment

(c)

Chloro-phyll a Chlorophyll b

Carotenoids

Wavelength of light (nm)

Ab

so

rpti

on

of

lig

ht

by

ch

loro

pla

st

pig

me

nts

Ra

te o

f p

ho

tos

yn

the

sis

(m

ea

su

red

by

O2

rele

as

e)

Aerobic bacteria

Filamentof alga

400 500 600 700

400 500 600 700

400 500 600 700

RESULTS

Slide 19

Pigments in chloroplastsPigments in chloroplasts

1.1. Chlorophyll Chlorophyll aa: absorbs blue-violet and : absorbs blue-violet and redred

2.2. Chlorophyll Chlorophyll bb: absorbs blue and : absorbs blue and orangeorange

3.3. Carotenoids: absorbs other Carotenoids: absorbs other wavelengthswavelengths

4.4. Other pigments: found in various Other pigments: found in various plantsplants

Figure 10.11

Hydrocarbon tail(H atoms not shown)

Porphyrin ring

CH3

CH3 in chlorophyll aCHO in chlorophyll b

Chlo

rophyll

Chlo

rophyll

Slide 21

““Excited” electronsExcited” electrons

• Ground state – where the electron is normallyGround state – where the electron is normally

• Excited state – where the electron is when it Excited state – where the electron is when it becomes excited (usually an energy level farther becomes excited (usually an energy level farther from the nucleus)from the nucleus)

• More unstableMore unstable

• More potential energyMore potential energy

Figure 10.12

Excitedstate

Heat

e

Photon(fluorescence)

Groundstate

PhotonChlorophyll

molecule

En

erg

y o

f el

ectr

on

(a) Excitation of isolated chlorophyll molecule (b) Fluorescence

““Falling” electrons release energyFalling” electrons release energy

Figure 10.13a

(a) How a photosystem harvests light

Th

ylak

oid

mem

bra

ne

PhotonPhotosystem STROMA

Light-harvestingcomplexes

Reaction-centercomplex

Primaryelectronacceptor

Transferof energy

Special pair ofchlorophyll amolecules

Pigmentmolecules

THYLAKOID SPACE(INTERIOR OF THYLAKOID)

e

Slide 24

PhotosystemsPhotosystems

There are two photsystems in plants:There are two photsystems in plants:

• Photosystem II (P680): reaction center Photosystem II (P680): reaction center chlorophyll a absorbs light at 680 nmchlorophyll a absorbs light at 680 nm

• Photosystem I (P700): reaction center Photosystem I (P700): reaction center chlorophyll a absorbs light at 700 nmchlorophyll a absorbs light at 700 nm

Slide 25

The Light ReactionsThe Light Reactions

• Sunlight used to make ATP and NADPH for the Sunlight used to make ATP and NADPH for the Calvin CycleCalvin Cycle

• Works by exciting electrons so that when they Works by exciting electrons so that when they “fall”:“fall”:

1. The energy can be captured to make ATP1. The energy can be captured to make ATP

2. The electrons can be placed on NADPH 2. The electrons can be placed on NADPH

Figure 10.14-1

Primaryacceptor

P680

Light

Pigmentmolecules

Photosystem II(PS II)

1

2e

Linear Electron FlowLinear Electron Flow

Figure 10.14-2

Primaryacceptor

H2O

O2

2 H

+1/2

P680

Light

Pigmentmolecules

Photosystem II(PS II)

1

2

3

e

e

e

Linear Electron Flow (cont.)Linear Electron Flow (cont.)

Figure 10.14-3

Cytochromecomplex

Primaryacceptor

H2O

O2

2 H

+1/2

P680

Light

Pigmentmolecules

Photosystem II(PS II)

Pq

Pc

ATP

1

2

3

5

Electron transport chaine

e

e

4

Linear Electron Flow (cont.)Linear Electron Flow (cont.)

Figure 10.14-4

Cytochromecomplex

Primaryacceptor

Primaryacceptor

H2O

O2

2 H

+1/2

P680

Light

Pigmentmolecules

Photosystem II(PS II)

Photosystem I(PS I)

Pq

Pc

ATP

1

2

3

5

6

Electron transport chain

P700

Light

e

e

4

e

e

Linear Electron Flow (cont.)Linear Electron Flow (cont.)

Figure 10.14-5

Cytochromecomplex

Primaryacceptor

Primaryacceptor

H2O

O2

2 H

+1/2

P680

Light

Pigmentmolecules

Photosystem II(PS II)

Photosystem I(PS I)

Pq

Pc

ATP

1

2

3

5

6

7

8

Electron transport chain

Electron

transport

chain

P700

Light

+ HNADP

NADPH

NADP

reductase

Fd

e

e

e

e

4

e

e

Linear Electron Flow (cont.)Linear Electron Flow (cont.)

Figure 10.15

Photosystem II Photosystem I

Millmakes

ATP

ATP

NADPH

e

e

e

ee

e

e

Ph

oto

n

Ph

oto

n

Figure 10.16

Photosystem I

Primaryacceptor

Cytochromecomplex

Fd

Pc

ATP

Primaryacceptor

Pq

Fd

NADPH

NADP

reductase

NADP

+ H

Photosystem II

Cyclic Electron FlowCyclic Electron Flow

Figure 10.17Mitochondrion Chloroplast

MITOCHONDRIONSTRUCTURE

CHLOROPLASTSTRUCTURE

Intermembranespace

Innermembrane

Matrix

Thylakoidspace

Thylakoidmembrane

Stroma

Electrontransport

chain

H Diffusion

ATPsynthase

H

ADP P iKey Higher [H ]

Lower [H ]

ATP

Figure 10.18

STROMA(low H concentration)

STROMA(low H concentration)

THYLAKOID SPACE(high H concentration)

Light

Photosystem II

Cytochromecomplex Photosystem I

Light

NADP

reductase

NADP + H

ToCalvinCycle

ATPsynthase

Thylakoidmembrane

2

1

3

NADPH

Fd

Pc

Pq

4 H+

4 H++2 H+

H+

ADP+P i

ATP

1/2

H2OO2

Chemiosmosis (…again)Chemiosmosis (…again)

Slide 35

PhotophosphorylatiPhotophosphorylation vs. Oxidative on vs. Oxidative PhosphorylationPhosphorylation

How are they different?:How are they different?:

1.1. Source of the Source of the electronselectrons

Photo ________Photo ________

Oxi __________Oxi __________

2.2. Source of the energySource of the energy

Photo Photo ________________

Oxi Oxi ____________________

3.3. Fate of the electronsFate of the electrons

Photo ________Photo ________

Oxi __________Oxi __________

Slide 36

Input

CO2

ATP

NADPH

CALVINCYCLE

Output: G3P

The The Calvin Calvin CycleCycle

Figure 10.19-1Input

3 (Entering oneat a time)

CO2

Phase 1: Carbon fixation

Rubisco

3 P P

P6

Short-livedintermediate

3-Phosphoglycerate3 P P

Ribulose bisphosphate(RuBP)

Figure 10.19-2Input

3 (Entering oneat a time)

CO2

Phase 1: Carbon fixation

Rubisco

3 P P

P6

Short-livedintermediate

3-Phosphoglycerate6

6 ADP

ATP

6 P P1,3-Bisphosphoglycerate

CalvinCycle

6 NADPH

6 NADP

6 P i

6 P

Phase 2: Reduction

Glyceraldehyde 3-phosphate(G3P)

3 P PRibulose bisphosphate

(RuBP)

1 PG3P

(a sugar)Output

Glucose andother organiccompounds

Figure 10.19-3Input

3 (Entering oneat a time)

CO2

Phase 1: Carbon fixation

Rubisco

3 P P

P6

Short-livedintermediate

3-Phosphoglycerate6

6 ADP

ATP

6 P P1,3-Bisphosphoglycerate

CalvinCycle

6 NADPH

6 NADP

6 P i

6 P

Phase 2: Reduction

Glyceraldehyde 3-phosphate(G3P)

P5G3P

ATP

3 ADP

Phase 3:Regeneration ofthe CO2 acceptor(RuBP)

3 P PRibulose bisphosphate

(RuBP)

1 PG3P

(a sugar)Output

Glucose andother organiccompounds

3

Slide 40Fig. 10-21

LightReactions:

Photosystem II Electron transport chain

Photosystem I Electron transport chain

CO2

NADP+

ADP

P i+

RuBP 3-Phosphoglycerate

CalvinCycle

G3PATP

NADPHStarch(storage)

Sucrose (export)

Chloroplast

Light

H2O

O2

Figure 10.21

Sugarcane

Mesophyllcell

Bundle-sheathcell

C4 CO2

Organic acid

CO2

CalvinCycle

Sugar

(a) Spatial separation of steps (b) Temporal separation of steps

CO2

Organic acid

CO2

CalvinCycle

Sugar

Day

Night

CAM

Pineapple

CO2 incorporated(carbon fixation)

CO2 releasedto the Calvincycle

2

1

Wate

r Savin

g A

dapta

tions

Wate

r Savin

g A

dapta

tions

Slide 42

Greenhouse EffectGreenhouse Effect

Sunlight

Radiant heattrapped by CO2

and other gases

Atmosphere

Some heatenergy escapesinto space

Slide 43

So what?So what?

Slide 44

Slide 45