Download Photosynthesis

Photosynthesis:
Energy
From
Sunlight
The Ingredients For Photosynthesis
Sunlight
Sugars
Leaf
Stem
Root
Leaves: Plant Solar Collectors
Stoma
Plant Cell Structure
A
PLANT
CELL
Free
ribosomes
Nucleolus
Nucleus
Peroxisome
Smooth
endoplasmic
reticulum
Rough
endoplasmic
reticulum
Plasma
membrane
Plasmodesmata
Chloroplast
Mitochondrion
Golgi
apparatus
The Plant Cell Wall
Cell
wall
of
cell
1
Middle
lamella
Interior
of
cell
1
Plasma
membrane
Interior
of
cell
2
Cell
wall
of
cell
2
Plant Cell Structure
Free
ribosomes
A
PLANT
CELL
Cell
wall
Vacuole
Peroxisome
Nucleolus
Nucleus
Rough
endoplasmic
reticulum
Smooth
endoplasmic
reticulum
Plasma
membrane
Plasmodesmata
Chloroplast
Mitochondrion
Golgi
apparatus
The Photosynthetic Reactions Are Carried Out By Chloroplasts
Chloroplast Structure
Inner
membrane
Outer
membrane
Thylakoid
Stroma
Granum
(stack
of
thylakoids)
Photosynthesis Is A Two-Step Process
Chloroplast
Light
(photon)
ELECTRON
TRANSPORT
Thylakoid
Light
reactions
Chlorophyl
ATP
CYCLE
Light‐
independent
reactions
NADPH
CYCLE
CALVIN
CYCLE
Stroma
The Light Reactions
Light
Reactions
The Electromagnetic Spectrum
Action Spectrum Of Photosynthesis
Chlorophyll
Figure 10.5 Exciting An Atom
Increasing
energy
Excited
state
Absorption
of
photon
by
molecule
Photon
Ground
state
Photon
Electron
Nucleus
Ground
state
Excited
state
Photoexcitation Of Chlorophyll
Chlorophyll Molecules Are Found In Large Protein Complexes
(CHO
in
chlorophyll
b)
Chlorophyll
molecules
Proteins
Stroma
Thylakoid
membrane
Thylakoid
lumen
Photosystems Consist Of Two Parts
1. Photosynthetic Reaction Center
2. Antenna Complex
Plants And Cyanobacteria Possess Two Photosystems
Far‐red
light
on
Off
Red
light
on
Off
Both
lights
on
Off
Comparative Photosystem Organization
Red, photochemical reaction center molecules; green, light harvesting pigments
Note: PsaA and PsaB are like D2-Core antenna protein and D1-Core antenna protein fusions, respectively Photosystems Consist Of Two Parts
1. Photosynthetic Reaction Center
2. Antenna Complex
Organization Of Pigment Molecules
Summary Electron Transfer Reactions Within the Reaction Center
Figure 14-45 Molecular Biology of the Cell (© Garland Science 2008)
Electron Transfer Reactions Within A Purple Bacterial Photosystem
Need to capture 2 photons of light to reduce Quinone
Figure 14-46 Molecular Biology of the Cell (© Garland Science 2008)
Comparative Photosystem Organization
Red, photochemical reaction center molecules; green, light harvesting pigments
Note: PsaA and PsaB are like D2-Core antenna protein and D1-Core antenna protein fusions, respectively Plant Photosystem II Structure
PSII is a dimer Each monomer contains:
16 Integral membrane protein subunits
3 subunits in the lumen
3 subunits in the lumen
36 chlorohylls
7 carotenoids
2 pheophytins
2 hemes
2 plastoquinones
1 Mn water splitting complex
Figure 14-47a,c Molecular
Biology of the Cell (© Garland
Science 2008)
Plant Photosystem II Structure
Figure 14-47b Molecular Biology of the Cell (©
Garland Science 2008)
Light Reactions Take Place On Thylakoid Membranes
Chloroplast
Thylakoid
Electron Transport Pathway Of Photosynthesis Mobile Carriers: Plastoquinone (PQ; organic molecule) and Plastocyanine (PC, Protein)
Large Complexes: Photosystem II, Photosystem I, Cytochrome B6-f Complex (Cyt)
Thylakoid
interior
ELECTRON
TRANSPORT
(high
concentration
of
H+)
H2O
1/2
O2
ATP
SYNTHESIS
PC
ATP
synthase
2
PQ
Cyt
Photon
Photosystem
II
Stroma
(low
concentration
of
H+)
Photon
Fd
Photosystem
I
NADP
Reductase
Topology Of Chloroplast Photosynthetic Components
Figure 14-48 Molecular Biology of the Cell (© Garland Science 2008)
Energetics Of Non-Cyclic Photophosphorylation
Figure 14-49
Molecular Biology of
the Cell (© Garland
Science 2008)
Cyclic And Non-Cyclic Photophosphorylation
PS
I
Cyclic
Photophosphorylation
PS
II
Figure 14-73 (part 2 of 3) Molecular Biology of the Cell (© Garland Science 2008)
Chemiosmotic ATP Generation
ATP Synthase
Figure 14-15 Molecular Biology of the Cell (© Garland Science 2008)
Chemiosmotic ATP Synthesis
Figure 14-19 Molecular Biology of the Cell (© Garland Science 2008)
Non-Cyclic Photophosphorylation Summary
4 Stages:
1.
2.
3.
4.
Light energy is used to energize an electron that can drive electron transport system
Electron transport system generates proton gradient across thylakoid membrane
Electron transport system reduces NADP+
Proton gradient is used to chemiosmotically generate ATP
Dark
Reactions
Ribulose 1-5-Bisphosphate Carboxylase-Oxygenase
(RuBisCO): The First Step Of The Dark Reactions
(RuBP)
Figure 14-39 Molecular Biology of the Cell (© Garland Science 2008)
(Unstable)
The First Stable Product Containing Fixed Carbon From Carbon Dioxide
Carboxyl
group
3‐Phosphoglycerate
(3PG)
The
Dark
Reactions
Photon
Thylakoid
ELECTRON
TRANSPORT
ATP
CYCLE
Stroma
CALVIN
CYCLE
NADPH
CYCLE
The Calvin Cycle
The Calvin Cycle
START
6
RuBP
Carbon
fixation
6
RuMP
12
3PG
CALVIN
CYCLE
Regeneration
Reduction
and
of
RuBP
sugar
production
10
G3P
12
G3P
2
G3P
Sugars
Other
carbon
compounds
Used For All Plant Carbon Metabolism
Glyceraldehyde
3‐phosphate
(G3P)
Overview Of Photosynthetic Reactions
Metabolic Interactions In A Plant Cell
Lipids
(triglycerides)
Glycerol
3PG
RuBP
CALVIN
CYCLE
RuMP
Nucleotides
Nucleic
acids
Fatty
acids
Pyruvate
G3P
Acetyl
CoA
GLYCOLYSIS
GLUCONEOGENESIS
Hexose‐P
Sucrose
Polysaccharides
(e.g.,
starch,
cellulose)
Metabolic Interactions In A Plant Cell
Nitrogen
from
soil
Acetyl
CoA
NH4+
α‐ketoglutarate
CITRIC
ACID
CYCLE
Amino
acids
Proteins
Energy Losses During Photosynthesis
ENERGY
LOSS
SUNLIGHT
100%
50%
Wavelengths
of
light
not
part
of
absorption
spectrum
of
photosynthetic
pigments
(e.g.,
green
light)
30%
Light
energy
not
absorbed
due
to
plant
structure
(e.g.,
leaves
not
properly
oriented
to
sun)
10%
Inefficiency
of
light
reactions
converting
light
to
chemical
energy
Wavelengths
of
light
that
can
be
absorbed
by
photosynthetic
pigments
Light
energy
absorbed
by
photosynthetic
pigments
Chemical
energy
available
for
CO2
fixation
Chemical
energy
stored
Chemical
energy
stored
in
carbohydrates
in
carbohydrates
5%
5%
5%
Inefficiency
of
CO2
fixation
pathways
Net
chemical
energy
stored
in
carbohydrates
from
sunlight:
5%
Photorespiration
Carbon
lost
Carbon
gained
2‐PG
Carboxylase
reaction
Photorespiration
Rubisco
Oxygenase
reaction
Calvin
cycle
3‐PGA
C3 and C4 Leaves Have Different Anatomy
The Anatomy and Biochemistry of C4 Carbon Fixation
Mesophyll
cell
Mesophyll
cell
Bundle
sheath
cell
The Anatomy and Biochemistry of C4 Carbon Fixation
Plasma
membrane
Cell
wall
PEP
Mesophyll
cell
Carboxy‐
lation
C4
cycle
4C
compound
Bundle
sheath
cell
Regener‐
ation
3C
compound
4C
compound
3C
compound
Decarb‐
oxylation
5C
sugar
Regener‐
ation
Carboxy‐
Calvin
Cycle
lation
Triose‐P
3C
sugar
Note: the Calvin Cycle that occurs in Bundle Sheath Cells is the standard dark reactions occurring in all plants
The
CAM
C4
Pathway