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Chapter 10: Photosynthesis. (b). Multicellular alga. (c). Unicellular protists. (e). Purple sulfur bacteria. Figure 10.2. (a) Plants. (d) Cyanobacteria. 40  m. 10  m. 1  m. Sunlight energy. ECOSYSTEM. Photosynthesis in chloroplasts. CO 2. Glucose. H 2 O. O 2.

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slide1

Chapter 10:

Photosynthesis

figure 10 2

(b)

Multicellularalga

(c)

Unicellularprotists

(e)

Purple sulfurbacteria

Figure 10.2

(a) Plants

(d) Cyanobacteria

40 m

10 m

1 m

slide3

Sunlight energy

ECOSYSTEM

Photosynthesis

in chloroplasts

CO2

Glucose

H2O

O2

Cellular respiration

in mitochondria

ATP

(for cellular work)

Heat energy

What we (should) already know!

slide4

Plants are producers

  • Autotrophs – make their own organic molecules from inorganic carbon (CO2)
      • Photoautotrophs – use light to make organic molecules
  • Heterotrophs - obtain organic molecules from another organism
      • Consumers
      • Decomposers
figure 10 4a

Leaf cross section

Chloroplasts

Vein

Mesophyll

Figure 10.4a

Leaf Structure

Stomata

CO2

O2

Chloroplast

Mesophyllcell

20 m

figure 10 4b

Chloroplast

Figure 10.4b

Outermembrane

Chloroplasts

Thylakoid

Intermembranespace

Granum

Stroma

Thylakoidspace

Innermembrane

1 m

figure 10 5

Photosynthesis

Figure 10.5

Reactants:

6 CO2

12 H2O

6 H2O

Products:

C6H12O6

6 O2

slide8

Tracer Experiment

  • Used radiolabeled oxygen atoms in the reactants to determine which contributed the O2 that is released by plants
      • Could be from CO2 or H2O
slide9

Oxidation-Reduction Reactions (Redox)

  • Occurs when electrons are moved from one molecule to another
        • The molecule that loses the electron(s) is OXIDIZED (called oxidation)
        • The molecule that gains the electron(s) is REDUCED (called reductions)
  • They will always go together
  • As electrons move, they gain potential energy (in photosynthesis)
  • In photosynthesis, electrons move from water to CO2, forming sugars
figure 10 un01

Photosynthesis is a Redox Reaction

Figure 10.UN01

becomes reduced

C6 H12 O6 6 O2

Energy  6 CO2  6 H2O

becomes oxidized

figure 10 6 1

H2O

Light

NADP

Figure 10.6-1

ADP

+P i

LightReactions

Chloroplast

figure 10 6 2

H2O

Light

NADP

Figure 10.6-2

ADP

+P i

LightReactions

ATP

NADPH

Chloroplast

O2

figure 10 6 3

CO2

H2O

Light

NADP

Figure 10.6-3

ADP

+P i

CalvinCycle

LightReactions

ATP

NADPH

Chloroplast

O2

figure 10 6 4

CO2

H2O

Light

NADP

Figure 10.6-4

ADP

+P i

CalvinCycle

LightReactions

ATP

NADPH

Chloroplast

[CH2O](sugar)

O2

figure 10 7

1 m

103 nm

1 nm

105 nm

103 nm

106 nm

103 m

(109 nm)

Radiowaves

Micro-waves

Gammarays

UV

X-rays

Infrared

Figure 10.7

Electromagnetic Spectrum

Visible light

380

700

550

600

650

450

500

750 nm

Longer wavelength

Shorter wavelength

Higher energy

Lower energy

figure 10 8

Chloroplasts absorb only certain colors

Light

Reflectedlight

Chloroplast

Figure 10.8

Absorbedlight

Granum

Transmittedlight

figure 10 9

TECHNIQUE

Chlorophyllsolution

Photoelectrictube

Refractingprism

Whitelight

Galvanometer

Figure 10.9

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

Greenlight

Slit moves topass lightof selectedwavelength.

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

Bluelight

figure 10 10

Absorptionspectra

(a)

(c)

Engelmann’sexperiment

RESULTS

Chloro-phyll a

Chlorophyll b

Absorption of light bychloroplast pigments

Carotenoids

500

600

700

400

Figure 10.10

Wavelength of light (nm)

Rate of photosynthesis (measured by O2 release)

400

500

600

700

(b) Action spectrum

Aerobic bacteria

Filamentof alga

400

500

600

700

slide19

Pigments in chloroplasts

  • Chlorophyll a: absorbs blue-violet and red
  • Chlorophyll b: absorbs blue and orange
  • Carotenoids: absorbs other wavelengths
  • Other pigments: found in various plants
figure 10 11

CH3 in chlorophyll a

CH3

CHO in chlorophyll b

Porphyrin ring

Figure 10.11

Chlorophyll

Hydrocarbon tail(H atoms not shown)

slide21

“Excited” electrons

  • Ground state – where the electron is normally
  • Excited state – where the electron is when it becomes excited (usually an energy level farther from the nucleus)
      • More unstable
      • More potential energy
figure 10 12

“Falling” electrons release energy

Excitedstate

e

Figure 10.12

Heat

Energy of electron

Photon(fluorescence)

Photon

Groundstate

Chlorophyllmolecule

(a) Excitation of isolated chlorophyll molecule

(b) Fluorescence

figure 10 13a

Photosystem

STROMA

Photon

Light-harvestingcomplexes

Reaction-centercomplex

Primaryelectronacceptor

Figure 10.13a

e

Thylakoid membrane

Pigmentmolecules

Special pair ofchlorophyll amolecules

Transferof energy

THYLAKOID SPACE(INTERIOR OF THYLAKOID)

(a) How a photosystem harvests light

slide24

Photosystems

  • There are two photsystems in plants:
    • Photosystem II (P680): reaction center chlorophyll a absorbs light at 680 nm
    • Photosystem I (P700): reaction center chlorophyll a absorbs light at 700 nm
slide25

The Light Reactions

  • Sunlight used to make ATP and NADPH for the Calvin Cycle
  • Works by exciting electrons so that when they “fall”:
      • 1. The energy can be captured to make ATP
      • 2. The electrons can be placed on NADPH
figure 10 14 1

2

1

Linear Electron Flow

Primaryacceptor

Figure 10.14-1

e

P680

Light

Pigmentmolecules

Photosystem II(PS II)

figure 10 14 2

2

3

1

Linear Electron Flow (cont.)

Primaryacceptor

Figure 10.14-2

e

H2O

2 H

+

O2

1/2

e

e

P680

Light

Pigmentmolecules

Photosystem II(PS II)

figure 10 14 3

2

3

1

5

4

Linear Electron Flow (cont.)

Primaryacceptor

Electron transport chain

Pq

Figure 10.14-3

e

H2O

Cytochromecomplex

2 H

+

O2

1/2

Pc

e

e

P680

Light

ATP

Pigmentmolecules

Photosystem II(PS II)

figure 10 14 4

2

3

1

4

5

6

Linear Electron Flow (cont.)

Primaryacceptor

Primaryacceptor

Electron transport chain

e

Pq

Figure 10.14-4

e

H2O

Cytochromecomplex

2 H

+

O2

1/2

Pc

e

e

P700

P680

Light

Light

ATP

Pigmentmolecules

Photosystem I(PS I)

Photosystem II(PS II)

figure 10 14 5

2

8

3

1

5

4

6

7

Linear Electron Flow (cont.)

Electron transport chain

Primaryacceptor

Primaryacceptor

Electron transport chain

Fd

e

Pq

Figure 10.14-5

e

e

e

NADP

H2O

Cytochromecomplex

2 H

+ H

NADPreductase

+

O2

NADPH

1/2

Pc

e

e

P700

P680

Light

Light

ATP

Pigmentmolecules

Photosystem I(PS I)

Photosystem II(PS II)

figure 10 15

e

e

e

MillmakesATP

Figure 10.15

NADPH

e

e

e

Photon

e

ATP

Photon

Photosystem II

Photosystem I

figure 10 16

Cyclic Electron Flow

Primaryacceptor

Primaryacceptor

Fd

Fd

Figure 10.16

NADP+ H

Pq

NADPreductase

Cytochromecomplex

NADPH

Pc

Photosystem I

ATP

Photosystem II

figure 10 17

Chloroplast

Mitochondrion

Figure 10.17

CHLOROPLASTSTRUCTURE

MITOCHONDRIONSTRUCTURE

Diffusion

H

Thylakoidspace

Intermembranespace

Electrontransportchain

Thylakoidmembrane

Innermembrane

ATPsynthase

Matrix

Stroma

ADP  Pi

ATP

Key

Higher [H ]

H

Lower [H ]

figure 10 18

2

1

3

Chemiosmosis (…again)

STROMA(low H concentration)

Cytochromecomplex

NADPreductase

Photosystem I

Photosystem II

Light

4 H+

Light

NADP + H

Fd

Figure 10.18

Pq

NADPH

Pc

H2O

O2

1/2

THYLAKOID SPACE(high H concentration)

4 H+

+2 H+

ToCalvinCycle

Thylakoidmembrane

ATPsynthase

ADP+P i

ATP

STROMA(low H concentration)

H+

slide35

How are they different?:

  • Source of the electrons
      • Photo ________
      • Oxi __________
  • Source of the energy
    • Photo ________
    • Oxi __________
  • Fate of the electrons
      • Photo ________
      • Oxi __________

Photophosphorylation vs. Oxidative Phosphorylation

slide36

CO2

ATP

Input

NADPH

CALVIN

CYCLE

Output:

G3P

The Calvin Cycle

figure 10 19 1

Input

(Entering oneat a time)

3

CO2

Phase 1: Carbon fixation

Rubisco

3

P

P

Short-livedintermediate

Figure 10.19-1

6

P

P

3

P

Ribulose bisphosphate(RuBP)

3-Phosphoglycerate

figure 10 19 2

Input

(Entering oneat a time)

3

CO2

Phase 1: Carbon fixation

Rubisco

3

P

P

Short-livedintermediate

Figure 10.19-2

6

P

P

3

P

Ribulose bisphosphate(RuBP)

3-Phosphoglycerate

6

ATP

6 ADP

CalvinCycle

6

P

P

1,3-Bisphosphoglycerate

6 NADPH

6 NADP

6Pi

6

P

Glyceraldehyde 3-phosphate(G3P)

Phase 2: Reduction

1

P

G3P(a sugar)

Glucose andother organiccompounds

Output

figure 10 19 3

Input

(Entering oneat a time)

3

CO2

Phase 1: Carbon fixation

Rubisco

3

P

P

Short-livedintermediate

Figure 10.19-3

6

P

P

3

P

Ribulose bisphosphate(RuBP)

3-Phosphoglycerate

6

ATP

6 ADP

3 ADP

CalvinCycle

6

P

P

3

ATP

1,3-Bisphosphoglycerate

6 NADPH

Phase 3:Regeneration ofthe CO2 acceptor(RuBP)

6 NADP

6Pi

P

5

G3P

6

P

Glyceraldehyde 3-phosphate(G3P)

Phase 2: Reduction

1

P

G3P(a sugar)

Glucose andother organiccompounds

Output

fig 10 21

H2O

CO2

Light

NADP+

ADP

Fig. 10-21

P

+

i

Light

Reactions:

Photosystem II

Electron transport chain

Photosystem I

Electron transport chain

RuBP

3-Phosphoglycerate

Calvin

Cycle

ATP

G3P

Starch

(storage)

NADPH

Chloroplast

O2

Sucrose (export)

figure 10 21

1

2

Figure 10.21

Sugarcane

Pineapple

Water Saving Adaptations

C4

CAM

CO2

CO2

CO2 incorporated(carbon fixation)

Night

Mesophyllcell

Organic acid

Organic acid

CO2

CO2

Day

Bundle-sheathcell

CO2 releasedto the Calvincycle

CalvinCycle

CalvinCycle

Sugar

Sugar

(a) Spatial separation of steps

(b) Temporal separation of steps

slide42

Some heat

energy escapes

into space

Sunlight

Atmosphere

Radiant heat

trapped by CO2

and other gases

Greenhouse Effect