(a) Plants
(c) Unicellular protist
10 µm
(e) Purple sulfur
bacteria
(b) Multicellular alga
(d) Cyanobacteria
40 µm
1.5 µm
1
Leaf cross section
Vein
Mesophyll
Stomata
Chloroplast
CO2
O2
Mesophyll cell
Outer
membrane
Thylakoid
Stroma
Granum
Thylakoid
space
Intermembrane
space
5 µm
Inner
membrane
1 µm
2
Reactants:
Products:
6 CO2
C6H12O6
12 H2O
6 H 2O
6 O2
3
CO2
H 2O
Light
NADP+
ADP
+ P i
Light
Reactions
Calvin
Cycle
ATP
NADPH
Chloroplast
O2
[CH2O]
(sugar)
4
10–5 nm 10–3 nm
103 nm
1 nm
Gamma
X-rays
rays
UV
106 nm
Infrared
1m
(109 nm)
Microwaves
103 m
Radio
waves
Visible light
380
450
500
Shorter wavelength
Higher energy
550
600
650
700
750 nm
Longer wavelength
Lower energy
5
Light
Reflected
light
Chloroplast
Absorbed
light
Granum
Transmitted
light
6
Absorption of light by
chloroplast pigments
RESULTS
Chlorophyll a
Carotenoids
400
(a) Absorption spectra
Chlorophyll b
500
600
700
(b) Action spectrum
Rate of photosynthesis
(measured by O2 release)
Wavelength of light (nm)
Aerobic bacteria
Filament
of alga
(c) Engelmann’s
experiment
400
500
600
700
7
CH3
CHO
in chlorophyll a
in chlorophyll b
Porphyrin ring:
light-absorbing
“head” of molecule;
note magnesium
atom at center
Hydrocarbon tail:
interacts with hydrophobic
regions of proteins inside
thylakoid membranes of
chloroplasts; H atoms not
shown
8
Energy of electron
e–
Excited
state
Heat
Photon
(fluorescence)
Photon
Chlorophyll
molecule
Ground
state
(a) Excitation of isolated chlorophyll molecule
(b) Fluorescence
9
Photosystem
STROMA
Light-harvesting Reaction-center
complex
complexes
Primary
electron
acceptor
Thylakoid membrane
Photon
e–
Transfer
of energy
Special pair of
chlorophyll a
molecules
Pigment
molecules
THYLAKOID SPACE
(INTERIOR OF THYLAKOID)
10
Primary
acceptor
2
H+
+
1/ O
2
2
H 2O
e–
2
Primary
acceptor
4
e–
Pq
Cytochrome
complex
3
7
Fd
e–
e–
8
NADP+
reductase
Pc
e–
e–
NADP+
+ H+
NADPH
P700
5
P680
Light
1
Light
6
ATP
Pigment
molecules
Photosystem II
(PS II)
Photosystem I
(PS I)
11
e–
ATP
e–
e–
NADPH
e–
Mill
makes
ATP
e–
n
Photo
e–
Photon
e–
Photosystem II
Photosystem I
12
Primary
acceptor
Primary
acceptor
Fd
Fd
Pq
NADP+
reductase
Cytochrome
complex
NADP+
+ H+
NADPH
Pc
Photosystem I
Photosystem II
ATP
13
Mitochondrion
Chloroplast
MITOCHONDRION
STRUCTURE
CHLOROPLAST
STRUCTURE
H+
Intermembrane
space
Inner
membrane
Diffusion
Electron
transport
chain
Thylakoid
space
Thylakoid
membrane
ATP
synthase
Key
Higher [H+]
Lower [H+]
Stroma
Matrix
ADP + P i
H+
ATP
14
STROMA
(low H+ concentration)
Cytochrome
Photosystem I
complex
Light
Photosystem II
4 H+
Light
Fd
NADP+
reductase
H 2O
THYLAKOID SPACE
(high H+ concentration)
1
e–
Pc
2
1/
2
NADP+ + H+
NADPH
Pq
e–
3
O2
+2 H+
4 H+
To
Calvin
Cycle
Thylakoid
membrane
STROMA
(low H+ concentration)
ATP
synthase
ADP
+
Pi
ATP
H+
15
Input
3
(Entering one
at a time)
CO2
Phase 1: Carbon fixation
Rubisco
3 P
Short-lived
intermediate
P
6
P
3-Phosphoglycerate
3P
P
Ribulose bisphosphate
(RuBP)
6
ATP
6 ADP
3 ADP
3
Calvin
Cycle
6 P
P
1,3-Bisphosphoglycerate
ATP
6 NADPH
Phase 3:
Regeneration of
the CO2 acceptor
(RuBP)
6 NADP+
6 Pi
P
5
G3P
6
P
Glyceraldehyde-3-phosphate
(G3P)
1
Output
P
G3P
(a sugar)
Phase 2:
Reduction
Glucose and
other organic
compounds
16
The C4 pathway
C4 leaf anatomy
Mesophyll
cell
Mesophyll cell
Photosynthetic
cells of C4
Bundleplant leaf
sheath
cell
CO2
PEP carboxylase
PEP (3C)
ADP
Oxaloacetate (4C)
Vein
(vascular tissue)
Malate (4C)
Stoma
Bundlesheath
cell
ATP
Pyruvate (3C)
CO2
Calvin
Cycle
Sugar
Vascular
tissue
17
Sugarcane
Pineapple
C4
CAM
CO2
Mesophyll
cell
Organic acid
Bundlesheath
cell
CO2
1 CO2 incorporated
into four-carbon Organic acid
organic acids
(carbon fixation)
CO2
Calvin
Cycle
CO2
2 Organic acids
release CO2 to
Calvin cycle
Night
Day
Calvin
Cycle
Sugar
Sugar
(a) Spatial separation of steps
(b) Temporal separation of steps
18
H 2O
CO2
Light
NADP+
ADP
+ P
i
Light
Reactions:
Photosystem II
Electron transport chain
Photosystem I
Electron transport chain
RuBP
ATP
NADPH
3-Phosphoglycerate
Calvin
Cycle
G3P
Starch
(storage)
Chloroplast
O2
Sucrose (export)
19