chapter 10: photosynthesis 1.what is photosynthesis & what organisms do photosynthesis?...
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Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?
- Photosynthesis – conversion of light energy to chemical energy- Photoautotrophs
Figure 10.2 Photoautotrophs
(a) Plants
(b) Multicellular algae
(c) Unicellular protist 10 m
40 m(c) Cyanobacteria
1.5 m(d) Pruple sulfurbacteria
These organisms use light energy to drive the synthesis of organic molecules from carbon dioxideand (in most cases) water. They feed not onlythemselves, but the entire living world. (a) Onland, plants are the predominant producers offood. In aquatic environments, photosyntheticorganisms include (b) multicellular algae, suchas this kelp; (c) some unicellular protists, suchas Euglena; (d) the prokaryotes calledcyanobacteria; and (e) other photosyntheticprokaryotes, such as these purple sulfurbacteria, which produce sulfur (sphericalglobules) (c, d, e: LMs).
Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?
- Photosynthesis – conversion of light energy to chemical energy- Photoautotrophs
2. Where does photosynthesis occur?- Chloroplasts
Fig. 10.3 Focusing in on the location of photosynthesis in a plant
Mesophyll cell
Mesophyll
Vein
Stomata
CO2 O2
Chloroplast
5 µm
1 µm
Outermembrane
Intermembranespace
Inner membrane
Thylakoid ThylakoidSpace
GranumStroma
Leaf cross section
½ million chloroplasts / mm2 of leaf
30 – 40 chloroplasts / mesophyll cell
Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?2. Where does photosynthesis occur?3. How did chloroplasts evolve?
- Endosymbiosis- Chemoheterotroph engulfed a photoautotroph (Ch 26)
4. What is the chemical equation for photosynthesis?
CO2 + H2O + light energy → C6H12O6 + O2 + H2O (+ energy)
6 CO2 12 H2OReactants:
Products: C6H12O66 H2O 6 O2
Let’s see where this occurs in the chloroplast….The light reactions & the Calvin Cycle
Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle
Light
LIGHT REACTIONS
Chloroplast
H2O
Light rxns require light – light-dependent
Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle
ATP
NADPH
O2
H2O
Light
LIGHT REACTIONS
Chloroplast
Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle
Calvin Cycle – light-independent rxns
CO2
CALVINCYCLE
O2
[CH2O](sugar)
NADP
ADP+ P i
H2O
Light
LIGHT REACTIONS
Chloroplast
ATP
NADPH
Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?2. Where does photosynthesis occur?3. How did chloroplasts evolve?4. What is the chemical equation for photosynthesis?5. What are the colors of the rainbow (in order)?
ROY G BIV
Gammarays X-rays UV Infrared
Micro-waves
Radiowaves
10–5 nm 10–3 nm 1 nm 103 nm 106 nm1 m
106 nm 103 m
380 450 500 550 600 650 700 750 nm
Visible light
Shorter wavelength
Higher energy
Longer wavelength
Lower energy
Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?2. Where does photosynthesis occur?3. How did chloroplasts evolve?4. What is the chemical equation for photosynthesis?5. What are the colors of the rainbow (in order)?6. What 3 things can happen to light when it “hits” an object?
Light
ReflectedLight
Chloroplast
Absorbedlight
Granum
Transmittedlight
Figure 10.7 Why leaves are green: interaction of light with chloroplasts
What absorbs the light?- Photosynthetic pigments- chlorophyll a & b- carotenoids – broaden the spectrum of usable light
Figure 10.9 Inquiry Which wavelengths of light are most effective in driving photosynthesis?
Three different experiments helped reveal which wavelengths of light are photosynthetically important. The results are shown below.
EXPERIMENT
(a) Absorption spectra. The three curves show the wavelengths of light best absorbed by three types of chloroplast pigments.
RESULTSA
bso
rptio
n o
f lig
ht
by
chlo
rop
last
pig
me
nts
400 500 600 700
Chlorophyll a
Chlorophyll b
Carotenoids
Wavelength of light (nm)
Rat
e o
f ph
otos
ynth
esis
(mea
sure
d by
O2 r
elea
se)
Action spectrum. This graph plots the rate of photosynthesis versus wavelength. The resulting action spectrum resembles the absorption spectrum for chlorophyll a but does not match exactly (see part a). This is partly due to the absorption of light by accessory pigments such as chlorophyll b and carotenoids.
(b)
400 500 600 700
Aerobic bacteria
Filamentof alga
Engelmann‘s experiment. In 1883, Theodor W. Engelmann illuminated a filamentous alga with light that had been passed through a prism, exposing different segments of the alga to different wavelengths. He used aerobic bacteria, which concentrate near an oxygen source, to determine which segments of the alga were releasing the most O2 and thus photosynthesizing most.Bacteria congregated in greatest numbers around the parts of the alga illuminated with violet-blue or red light. Notice the close match of the bacterial distribution to the action spectrum in part b.
(c)
Light in the violet-blue and red portions of the spectrum are most effective in driving photosynthesis.CONCLUSION
Rat
e o
f ph
otos
ynth
esis
(mea
sure
d by
O2 r
elea
se)
Action spectrum. This graph plots the rate of photosynthesis versus wavelength. The resulting action spectrum resembles the absorption spectrum for chlorophyll a but does not match exactly (see part a). This is partly due to the absorption of light by accessory pigments such as chlorophyll b and carotenoids.
(b)
400 500 600 700
Aerobic bacteria
Filamentof alga
Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?2. Where does photosynthesis occur?3. How did chloroplasts evolve?4. What is the chemical equation for photosynthesis?5. What are the colors of the rainbow (in order)?6. What 3 things can happen to light when it “hits” an object?7. What is the structure of chlorophyll?
Fig. 10.10 Structure of chlorophyll molecules in chloroplasts of plants
C
CH
CH2
CC
CC
C
CNNC
H3C
C
C
C
C C
C
C
C
N
CC
C
C N
MgH
H3C
H
C CH2CH3
H
CH3C
HHCH2
CH2
CH2
H CH3
C O
O
O
O
O
CH3
CH3
CHO
in chlorophyll a
in chlorophyll b
Porphyrin ring:Light-absorbing“head” of molecule;note magnesiumatom at center
Hydrocarbon tail:interacts with hydrophobicregions of proteins insidethylakoid membranes ofchloroplasts: H atoms notshown
Amphipathic – both polar & non-polar
Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?2. Where does photosynthesis occur?3. How did chloroplasts evolve?4. What is the chemical equation for photosynthesis?5. What are the colors of the rainbow (in order)?6. What 3 things can happen to light when it “hits” an object?7. What is the structure of chlorophyll?8. How do the photosystems harvest light energy?
Figure 10.11 Excitation of isolated chlorophyll by light
Excitedstate
Ene
rgy
of e
lect
ion
e–
Heat
Photon(fluorescence)
Chlorophyllmolecule
GroundstatePhoton
(a) Excitation of isolated chlorophyll molecule (b) Fluorescence
e–
Figure 10.12 How a photosystem harvests light
Primary electronacceptor
Photon
Thylakoid
Light-harvestingcomplexes
Reactioncenter
PhotosystemSTROMA
Thy
lako
id m
embr
ane
Transferof energy
Specialchlorophyll amolecules
Pigmentmolecules
THYLAKOID SPACE(INTERIOR OF THYLAKOID)
Figure 10.13 How noncyclic electron flow during the light reactions generates ATP and NADPH
H2O CO2
Light
LIGHT REACTIONS
CALVIN CYCLE
O2
NADP+
ADP
ATP
NADPH
[CH2O] (sugar)
Light
Photosystem II (PS II)
e
Primary acceptor
P6801
2
Ene
rgy
of e
lect
rons
Figure 10.13 How noncyclic electron flow during the light reactions generates ATP and NADPH
H2O CO2
Light
LIGHT REACTIONS
CALVIN CYCLE
O2
NADP+
NADPH
[CH2O] (sugar)
Light
Photosystem II (PS II)
e
Primary acceptor
ADP
ATP
2 H+
+
O21⁄2
H2O
e
e
1
3
2
Ene
rgy
of e
lect
rons
P680
Figure 10.13 How noncyclic electron flow during the light reactions generates ATP and NADPH
1
3O2
+
H2O CO2
Light
LIGHT REACTIONS
CALVIN CYCLE
O2
NADP+
NADPH
[CH2O] (sugar)
Light
Photosystem II (PS II)
e
Primary acceptor
ATP
2 H+
1⁄2
H2O2
Ene
rgy
of e
lect
rons
ADP
Pq
Cytochromecomplex
Pc
ATP
Electron transport chain
5
4
P680
e
e
Figure 10.13 How noncyclic electron flow during the light reactions generates ATP and NADPH
O2
H2O CO2
Light
LIGHT REACTIONS
CALVIN CYCLE
O2
NADPH
[CH2O] (sugar)
Light
Photosystem II (PS II)
e
Primary acceptor
2 H+
1⁄2
H2O2
Ene
rgy
of e
lect
rons
ADP
Pq
Cytochromecomplex
Pc
ATP
Electron transport chain
5
NADP+
ATP
Primary acceptor
e
Photosystem I (PS I)
Light
6
1
3
4
P680
P700
+
e
e
Figure 10.13 How noncyclic electron flow during the light reactions generates ATP and NADPH
P700
+
CO2
Photosystem II (PS II)
H2O
Light
LIGHT REACTIONS
CALVIN CYCLE
O2
NADPH
[CH2O] (sugar)
e
Primary acceptor
2 H+
1⁄2
H2O
e
e
1
Ene
rgy
of e
lect
rons
Pq
Cytochromecomplex
Pc
ATP
Electron transport chain
NADP+
Primary acceptor
e
Photosystem I (PS I)
Light
66
2
Light
ADP
ATP
5
Fd
ElectronTransportchain
7
NADP+
reductaseNADPH
NADP+
+ 2 H+
8
+ H+
1
3
4
P680
O2
e
e
Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?2. Where does photosynthesis occur?3. How did chloroplasts evolve?4. What is the chemical equation for photosynthesis?5. What are the colors of the rainbow (in order)?6. What 3 things can happen to light when it “hits” an object?7. What is the structure of chlorophyll?8. How do the photosystems harvest light energy?9. What’s the difference re: chemiosmosis in mitochondria & chloroplasts?
Figure 10.16 Comparison of chemiosmosis in mitochondria and chloroplasts
Key
Higher [H+]
Lower [H+]
Mitochondrion Chloroplast
MITOCHONDRIONSTRUCTURE
Intermembrancespace
Membrance
Matrix
Electrontransport
chain
H+ DiffusionThylakoidspace
Stroma
ATPH+
PADP+
ATPSynthase
CHLOROPLASTSTRUCTURE
Figure 10.17 The light reactions and chemiosmosis: the organization of the thylakoid membrane
LIGHTREACTOR
NADP+
ADP
ATP
NADPH
CALVINCYCLE
[CH2O] (sugar)STROMA(Low H+ concentration)
Photosystem II
LIGHT
H2O CO2
Cytochromecomplex
O2
H2OO2
1
1⁄2
2
Photosystem ILight
THYLAKOID SPACE(High H+ concentration)
STROMA(Low H+ concentration)
Thylakoidmembrane
ATPsynthase
PqPc
Fd
NADP+
reductase
NADPH + H+
NADP+ + 2H+
ToCalvincycle
ADP
PATP
3
H+
2 H++2 H+
2 H+
Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?2. Where does photosynthesis occur?3. How did chloroplasts evolve?4. What is the chemical equation for photosynthesis?5. What are the colors of the rainbow (in order)?6. What 3 things can happen to light when it “hits” an object?7. What is the structure of chlorophyll?8. How do the photosystems harvest light energy?9. What’s the difference chemiosmosis in mitochondria & chloroplasts?10. How do plants make “sugar?”
- Calvin Cycle
Figure 10.18 The Calvin cycle
LightH2O CO2
LIGHTREACTIONS
ATP
NADPH
NADP+
[CH2O] (sugar)
CALVINCYCLE
ADP
(Entering oneat a time)CO2
3
Phase 1: Carbon fixation
Rubisco
Short-livedintermediate
3 P P
3 P P
Ribulose bisphosphate(RuBP)
P
3-Phosphoglycerate6 ATP
6 ADP
Input
CALVINCYCLE
O2
6
Figure 10.18 The Calvin cycle
(Entering oneat a time)CO2
3
Phase 1: Carbon fixation
Rubisco
Short-livedintermediate
3 P P
3 P P
Ribulose bisphosphate(RuBP)
P
3-Phosphoglycerate
P6 P
1,3-Bisphosphoglycerate
6 NADPH
6 NADP+
6 P i
P6
Glyceraldehyde-3-phosphate(G3P)
Phase 2:Reduction
6 ATP
CALVINCYCLE
P1
G3P(a sugar)Output
Glucose andother organiccompounds
6 ADP
InputLightH2O CO2
LIGHTREACTIONS
ATP
NADP+
[CH2O] (sugar)
CALVINCYCLE
NADPH
ADP
O2
6
Figure 10.18 The Calvin cycle
(Entering oneat a time)CO2
3
Phase 1: Carbon fixation
Rubisco
Short-livedintermediate
3 P P
3 P P
Ribulose bisphosphate(RuBP)
P
3-Phosphoglycerate
P6 P
1,3-Bisphosphoglycerate
6 NADPH
6 NADP+
6 P i
P6
Glyceraldehyde-3-phosphate(G3P)
Phase 2:Reduction
6 ATP
3 ATP
3 ADP CALVINCYCLE
P5
Phase 3:Regeneration ofthe CO2 acceptor(RuBP)
P1
G3P(a sugar)Output
Glucose andother organiccompounds
G3P
6 ADP
LightH2O CO2
LIGHTREACTIONS
NADPH
NADP+
[CH2O] (sugar)
CALVINCYCLE
Input
ATP
ADP
O2
6
Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?2. Where does photosynthesis occur?3. How did chloroplasts evolve?4. What is the chemical equation for photosynthesis?5. What are the colors of the rainbow (in order)?6. What 3 things can happen to light when it “hits” an object?7. What is the structure of chlorophyll?8. How do the photosystems harvest light energy?9. What’s the difference chemiosmosis in mitochondria & chloroplasts?10. How do plants make “sugar?”11. How do plants get out of ATP debt?
- Cyclic electron flow
Figure 10.15 Cyclic electron flow
Primaryacceptor
Pq
Fd
Cytochromecomplex
Pc
Primaryacceptor
Fd
NADP+
reductase
NADPH
ATPPhotosystem II
(PS II)Photosystem I
(PS I)
NADP+
Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?2. Where does photosynthesis occur?3. How did chloroplasts evolve?4. What is the chemical equation for photosynthesis?5. What are the colors of the rainbow (in order)?6. What 3 things can happen to light when it “hits” an object?7. What is the structure of chlorophyll?8. How do the photosystems harvest light energy?9. What’s the difference chemiosmosis in mitochondria & chloroplasts?10. How do plants make “sugar?”11. How do plants get out of ATP debt?12. What is the difference between C3 & C4 photosynthesis?
Figure 10.19 C4 leaf anatomy and the C4 pathway
CO2
Mesophyll cell
Bundle-sheathcell
Vein(vascular tissue)
Photosyntheticcells of C4 plantleaf
Stoma
Mesophyllcell
C4 leaf anatomy
PEP carboxylase
Oxaloacetate (4 C) PEP (3 C)
Malate (4 C)
ADP
ATP
Bundle-Sheathcell CO2
Pyruate (3 C)
CALVINCYCLE
Sugar
Vasculartissue
CO2
Chapter 10: Photosynthesis1. What is photosynthesis & what organisms do photosynthesis?2. Where does photosynthesis occur?3. How did chloroplasts evolve?4. What is the chemical equation for photosynthesis?5. What are the colors of the rainbow (in order)?6. What 3 things can happen to light when it “hits” an object?7. What is the structure of chlorophyll?8. How do the photosystems harvest light energy?9. What’s the difference chemiosmosis in mitochondria & chloroplasts?10. How do plants make “sugar?”11. How do plants get out of ATP debt?12. What is the difference between C3 & C4 photosynthesis?13. How do CAM plants differ from C4 plants?
-Crassulacean Acid Metabolism
Figure 10.20 C4 and CAM photosynthesis compared
Organic acidsrelease CO2 toCalvin cycle
Spatial separation of steps. In C4 plants, carbon fixation and the Calvin cycle occur in differenttypes of cells.
(a) Temporal separation of steps. In CAM plants, carbon fixation and the Calvin cycle occur in the same cellsat different times.
(b)
PineappleSugarcane
Bundle-sheath cell
Mesophyll Cell
Organic acid
CALVINCYCLE
Sugar
CO2 CO2
Organic acid
CALVINCYCLE
Sugar
C4 CAM
CO2 incorporatedinto four-carbonorganic acids(carbon fixation)
Night
Day
1
2 Organic acidsrelease CO2 toCalvin cycle
CO2
Figure 10.21 A review of photosynthesis
Light reactions:• Are carried out by molecules in the thylakoid membranes• Convert light energy to the chemical energy of ATP and NADPH• Split H2O and release O2 to the atmosphere
Calvin cycle reactions:• Take place in the stroma• Use ATP and NADPH to convert CO2 to the sugar G3P• Return ADP, inorganic phosphate, and NADP+ to the light reactions
O2
CO2H2O
Light
Light reactions Calvin cycle
NADP+
ADP
ATP
NADPH
+ P 1
RuBP 3-Phosphoglycerate
Amino acidsFatty acids
Starch(storage)
Sucrose (export)
G3P
Photosystem IIElectron transport chain
Photosystem I
Chloroplast