Reece •Urry• Cain • Wasserman •Minorsky• Jackson ... 10 - Photosynthesis.pdf ·...
Transcript of Reece •Urry• Cain • Wasserman •Minorsky• Jackson ... 10 - Photosynthesis.pdf ·...
CAMPBELL
BIOLOGY Reece • Urry • Cain • Wasserman • Minorsky • Jackson
© 2014 Pearson Education, Inc.
TENTH EDITION
CAMPBELL
BIOLOGY Reece • Urry • Cain • Wasserman • Minorsky • Jackson
TENTH EDITION
10 Photosynthesis
Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick
© 2014 Pearson Education, Inc.
The Process That Feeds the Biosphere
! Photosynthesis is the process that converts solar energy into chemical energy
! Directly or indirectly, photosynthesis nourishes almost the entire living world
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! Autotrophs sustain themselves without eating anything derived from other organisms
! Autotrophs are the producers of the biosphere, producing organic molecules from CO2 and other inorganic molecules
! Almost all plants are photoautotrophs, using the energy of sunlight to make organic molecules
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Figure 10.1
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Figure 10.1a
Other organisms also benefit from photosynthesis.
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! Photosynthesis occurs in plants, algae, certain other unicellular eukaryotes, and some prokaryotes
! These organisms feed not only themselves but also most of the living world
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Figure 10.2
(a) Plants
(b) Multicellular alga
(c) Unicellular eukaryotes
(d) Cyanobacteria
(e) Purple sulfur bacteria
40 µm
1 µm
10 µ
m
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Figure 10.2a
(a) Plants
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Figure 10.2b
(b) Multicellular alga
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Figure 10.2c
(c) Unicellular eukaryotes 10 µ
m
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Figure 10.2d
(d) Cyanobacteria 40 µm
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Figure 10.2e
1 µm
(e) Purple sulfur bacteria
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! Heterotrophs obtain their organic material from other organisms
! Heterotrophs are the consumers of the biosphere
! Almost all heterotrophs, including humans, depend on photoautotrophs for food and O2
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! Earth’s supply of fossil fuels was formed from the remains of organisms that died hundreds of millions of years ago
! In a sense, fossil fuels represent stores of solar energy from the distant past
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Figure 10.3
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Concept 10.1: Photosynthesis converts light energy to the chemical energy of food ! Chloroplasts are structurally similar to and likely
evolved from photosynthetic bacteria
! The structural organization of these organelles allows for the chemical reactions of photosynthesis
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Chloroplasts: The Sites of Photosynthesis in Plants ! Leaves are the major locations of photosynthesis
! Chloroplasts are found mainly in cells of the mesophyll, the interior tissue of the leaf
! Each mesophyll cell contains 30–40 chloroplasts
! CO2 enters and O2 exits the leaf through microscopic pores called stomata
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! A chloroplast has an envelope of two membranes surrounding a dense fluid called the stroma
! Thylakoids are connected sacs in the chloroplast which compose a third membrane system
! Thylakoids may be stacked in columns called grana
! Chlorophyll, the pigment which gives leaves their green colour, resides in the thylakoid membranes
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Figure 10.4
Stroma Granum
Thylakoid Thylakoid space
Outer membrane
Intermembrane space Inner membrane
20 µm
Stomata
Chloroplast Mesophyll cell
1 µm
Mesophyll
Chloroplasts Vein Leaf cross section
CO2 O2
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Figure 10.4a Leaf cross section
Stomata
Chloroplast
Mesophyll
Chloroplasts Vein
Mesophyll cell
20 µm
CO2 O2
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Figure 10.4b
Chloroplast
Stroma Granum
Thylakoid Thylakoid space
Outer membrane
Intermembrane space Inner membrane
1 µm
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Figure 10.4c
Stroma Granum
1 µm
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Figure 10.4d
20 µm
Mesophyll cell
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Tracking Atoms Through Photosynthesis: Scientific Inquiry ! Photosynthesis is a complex series of reactions
that can be summarized as the following equation:
6 CO2 + 12 H2O + Light energy → C6H12O6 + 6 O2 + 6 H2O
! The overall chemical change during photosynthesis is the reverse of the one that occurs during cellular respiration
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The Splitting of Water
! Chloroplasts split H2O into hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules and releasing oxygen as a by-product
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Figure 10.5
Reactants:
Products:
6 CO2 12 H2O
C6H12O6 6 H2O 6 O2
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Photosynthesis as a Redox Process
! Photosynthesis reverses the direction of electron flow compared to respiration
! Photosynthesis is a redox process in which H2O is oxidized and CO2 is reduced
! Photosynthesis is an endergonic process; the energy boost is provided by light
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Figure 10.UN01
becomes reduced
becomes oxidized
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The Two Stages of Photosynthesis: A Preview
! Photosynthesis consists of the light reactions (the photo part) and Calvin cycle (the synthesis part)
! The light reactions (in the thylakoids)
! Split H2O
! Release O2
! Reduce the electron acceptor NADP+ to NADPH
! Generate ATP from ADP by photophosphorylation 29
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! The Calvin cycle (in the stroma) forms sugar from CO2, using ATP and NADPH
! The Calvin cycle begins with carbon fixation, incorporating CO2 into organic molecules
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Figure 10.6-1
Light
Thylakoid Stroma
Chloroplast
LIGHT REACTIONS
NADP+
ADP
P i +!
H2O
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Figure 10.6-2
Light
Thylakoid Stroma
Chloroplast
LIGHT REACTIONS
NADP+
ADP
P i +!
H2O
NADPH
ATP
O2
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Figure 10.6-3
Light
Thylakoid Stroma
Chloroplast
LIGHT REACTIONS
NADP+
ADP
P i +!
H2O
O2
CO2
NADPH
ATP
CALVIN CYCLE
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Figure 10.6-4
Light
Thylakoid Stroma
Chloroplast
LIGHT REACTIONS
NADP+
ADP
P i +!
H2O
[CH2O] (sugar)
CALVIN CYCLE
CO2
NADPH
ATP
O2
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BioFlix: The Carbon Cycle
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BioFlix: Photosynthesis
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Concept 10.2: The light reactions convert solar energy to the chemical energy of ATP and NADPH ! Chloroplasts are solar-powered chemical factories
! Their thylakoids transform light energy into the chemical energy of ATP and NADPH
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The Nature of Sunlight
! Light is a form of electromagnetic energy, also called electromagnetic radiation
! Like other electromagnetic energy, light travels in rhythmic waves
! Wavelength is the distance between crests of waves
! Wavelength determines the type of electromagnetic energy
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! The electromagnetic spectrum is the entire range of electromagnetic energy, or radiation
! Visible light consists of wavelengths (including those that drive photosynthesis) that produce colors we can see
! Light also behaves as though it consists of discrete particles, called photons
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Figure 10.7
Visible light
Gamma rays X-rays UV Infrared Micro-
waves Radio waves
380 450 500 550 600 650 700 750 nm Shorter wavelength
Higher energy Lower energy Longer wavelength
10− 5 10− 3nm nm 1 nm 3 nm 10 6 nm 10 9(10 nm) 1 m
10 3 m
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Photosynthetic Pigments: The Light Receptors
! Pigments are substances that absorb visible light
! Different pigments absorb different wavelengths
! Wavelengths that are not absorbed are reflected or transmitted
! Leaves appear green because chlorophyll reflects and transmits green light
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Figure 10.8
Light
Chloroplast
Reflected light
Granum
Transmitted light
Absorbed light
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Animation: Light and Pigments
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! A spectrophotometer measures a pigment’s ability to absorb various wavelengths
! This machine sends light through pigments and measures the fraction of light transmitted at each wavelength
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Figure 10.9
White light
Refracting prism
Chlorophyll solution
Photoelectric tube
Galvanometer
The high transmittance (low absorption) reading indicates that chlorophyll absorbs very little green light.
Slit moves to pass light of selected wavelength.
Green light
Blue light
The low transmittance (high absorption) reading indicates that chlorophyll absorbs most blue light.
1 2 3
4
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! An absorption spectrum is a graph plotting a pigment’s light absorption versus wavelength
! The absorption spectrum of chlorophyll a suggests that violet-blue and red light work best for photosynthesis
! An action spectrum profiles the relative effectiveness of different wavelengths of radiation in driving a process
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Figure 10.10 Chloro- phyll a Chlorophyll b
Carotenoids
400 500 600 700 Wavelength of light (nm)
(a) Absorption spectra
Abs
orpt
ion
of li
ght b
y ch
loro
plas
t pi
gmen
ts
Rat
e of
ph
otos
ynth
esis
(m
easu
red
by O
2 re
leas
e)
400 500 600 700
400 500 600 700
(b) Action spectrum
(c) Engelmann’s experiment
Aerobic bacteria
Filament of alga
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Figure 10.10a
Chloro- phyll a Chlorophyll b
Carotenoids
400 500 600 700 Wavelength of light (nm)
(a) Absorption spectra
Abs
orpt
ion
of li
ght b
y ch
loro
plas
t pi
gmen
ts
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Figure 10.10b
Rat
e of
ph
otos
ynth
esis
(m
easu
red
by O
2 re
leas
e)
400 500 600 700 (b) Action spectrum
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Figure 10.10c
400 500 600 700 (c) Engelmann’s experiment
Aerobic bacteria
Filament of alga
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! The action spectrum of photosynthesis was first demonstrated in 1883 by Theodor W. Engelmann
! In his experiment, he exposed different segments of a filamentous alga to different wavelengths
! Areas receiving wavelengths favorable to photosynthesis produced excess O2
! He used the growth of aerobic bacteria clustered along the alga as a measure of O2 production
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! Chlorophyll a is the main photosynthetic pigment
! Accessory pigments, such as chlorophyll b, broaden the spectrum used for photosynthesis
! The difference in the absorption spectrum between chlorophyll a and b is due to a slight structural difference between the pigment molecules
! Accessory pigments called carotenoids absorb excessive light that would damage chlorophyll
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Figure 10.11
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
CH in chlorophyll a in chlorophyll b
3 CHO CH 3
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Video: Space-Filling Model of Chlorophyll a
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! Accessory pigments called carotenoids function in photoprotection; they absorb excessive light that would damage chlorophyll
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Excitation of Chlorophyll by Light
! When a pigment absorbs light, it goes from a ground state to an excited state, which is unstable
! When excited electrons fall back to the ground state, photons are given off, an afterglow called fluorescence
! If illuminated, an isolated solution of chlorophyll will fluoresce, giving off light and heat
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Figure 10.12
Excited state
Heat
(a) Excitation of isolated chlorophyll molecule (b) Fluorescence
Ground state
Photon (fluorescence)
Photon Chlorophyll
molecule
Ener
gy o
f ele
ctro
n
e−
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Figure 10.12a
(b) Fluorescence 58
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A Photosystem: A Reaction-Center Complex Associated with Light-Harvesting Complexes ! A photosystem consists of a reaction-center
complex (a type of protein complex) surrounded by light-harvesting complexes
! The light-harvesting complexes (pigment molecules bound to proteins) transfer the energy of photons to the reaction center
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Figure 10.13
(a) How a photosystem harvests light (b) Structure of a photosystem
Chlorophyll STROMA
THYLA- KOID SPACE
Protein subunits
Thyl
akoi
d m
embr
ane
Pigment molecules
Primary electron acceptor
Reaction- center complex
STROMA
Photosystem
Light- harvesting complexes
Photon
Transfer of energy
Special pair of chloro- phyll a molecules
THYLAKOID SPACE (INTERIOR OF THYLAKOID)
Thyl
akoi
d m
embr
ane
e−
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Figure 10.13a
(a) How a photosystem harvests light
Pigment molecules
Primary electron acceptor
Reaction- center complex
STROMA
Photosystem
Light- harvesting complexes
Photon
Transfer of energy
Special pair of chloro- phyll a molecules
THYLAKOID SPACE (INTERIOR OF THYLAKOID)
Thyl
akoi
d m
embr
ane
e−
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Figure 10.13b
(b) Structure of a photosystem
Chlorophyll STROMA
THYLA- KOID SPACE
Protein subunits
Thyl
akoi
d m
embr
ane
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! A primary electron acceptor in the reaction center accepts excited electrons and is reduced as a result
! Solar-powered transfer of an electron from a chlorophyll a molecule to the primary electron acceptor is the first step of the light reactions
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! There are two types of photosystems in the thylakoid membrane
! Photosystem II (PS II) functions first (the numbers reflect order of discovery) and is best at absorbing a wavelength of 680 nm
! The reaction-center chlorophyll a of PS II is called P680
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! Photosystem I (PS I) is best at absorbing a wavelength of 700 nm
! The reaction-center chlorophyll a of PS I is called P700
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Linear Electron Flow
! During the light reactions, there are two possible routes for electron flow: cyclic and linear
! Linear electron flow, the primary pathway, involves both photosystems and produces ATP and NADPH using light energy
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! There are 8 steps in linear electron flow:
1. A photon hits a pigment and its energy is passed among pigment molecules until it excites P680
2. An excited electron from P680 is transferred to the primary electron acceptor (we now call it P680+)
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Figure 10.UN02
Light
H2O CO2
O2
LIGHT REACTIONS
CALVIN CYCLE
ATP
NADPH
ADP NADP+!
[CH2O] (sugar) 68
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Figure 10.14-1
Pigment molecules
e−
1
2
P680 Light
Photosystem II!(PS II)
Primary acceptor
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Figure 10.14-2
Pigment molecules
e−
1
2
P680 Light
Photosystem II!(PS II)
Primary acceptor
3e− e−
2 H+!
+!O2!
H2O!
½
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Figure 10.14-3
Pigment molecules
e−
1
2
P680 Light
Photosystem II!(PS II)
Primary acceptor
3e− e−
2 H+!
+!O2!
H2O!
ATP
4
5
Electron transport chain
Cytochrome complex
Pq
Pc ½
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Figure 10.14-4
Pigment molecules
e−
1
2
P680 Light
Photosystem II!(PS II)
Primary acceptor
3e− e−
2 H+!
+!O2!
H2O!
ATP
4
5
Electron transport chain
Cytochrome complex
Pq
Pc P700
Light
Photosystem I!(PS I)
6
Primary acceptor
e−
½
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Figure 10.14-5
Pigment molecules
e−
1
2
P680 Light
Photosystem II!(PS II)
Primary acceptor
3e− e−
2 H+!
+!O2!
H2O!
ATP
4
5
Electron transport chain
Cytochrome complex
Pq
Pc P700
Light
Photosystem I!(PS I)
6
Primary acceptor
e− e−
7
8Fd
e−
Electron transport chain
NADP+!
reductase NADPH
NADP+!
+ H+!
½
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3. H2O is split by enzymes, and the electrons are transferred from the hydrogen atoms to P680+, thus reducing it to P680
! P680+ is the strongest known biological oxidizing agent
! O2 is released as a by-product of this reaction
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4. Each electron “falls” down an electron transport chain from the primary electron acceptor of PS II to PS I
5. Energy released by the fall drives the creation of a proton gradient across the thylakoid membrane
! Diffusion of H+ (protons) across the membrane drives ATP synthesis
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6. In PS I (like PS II), transferred light energy excites P700, which loses an electron to an electron acceptor
! P700+ (P700 that is missing an electron) accepts an electron passed down from PS II via the electron transport chain
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7. Each electron “falls” down an electron transport chain from the primary electron acceptor of PS I to the protein ferredoxin (Fd)
8. The electrons are then transferred to NADP+ and reduce it to NADPH
! The electrons of NADPH are available for the reactions of the Calvin cycle
! This process also removes an H+ from the stroma
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! The energy changes of electrons during linear flow through the light reactions can be shown in a mechanical analogy
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Figure 10.15
Mill makes
ATP NADPH
Phot
on
Photosystem II! Photosystem I!
ATP
Phot
on
e−
e−
e− e−
e−
e−
e−
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Cyclic Electron Flow
! In cyclic electron flow, electrons cycle back from Fd to the PS I reaction center
! Cyclic electron flow uses only photosystem I and produces ATP, but not NADPH
! No oxygen is released
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Figure 10.16
Primary acceptor
Primary acceptor
Fd
Cytochrome complex
Pc
Pq
Photosystem II!Photosystem I!
Fd NADP+!
+ H+!NADP+!
reductase
NADPH!
ATP
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! Some organisms such as purple sulfur bacteria have PS I but not PS II
! Cyclic electron flow is thought to have evolved before linear electron flow
! Cyclic electron flow may protect cells from light-induced damage
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A Comparison of Chemiosmosis in Chloroplasts and Mitochondria ! Chloroplasts and mitochondria generate ATP by
chemiosmosis, but use different sources of energy
! Mitochondria transfer chemical energy from food to ATP; chloroplasts transform light energy into the chemical energy of ATP
! Spatial organization of chemiosmosis differs between chloroplasts and mitochondria but also shows similarities
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! In mitochondria, protons are pumped to the intermembrane space and drive ATP synthesis as they diffuse back into the mitochondrial matrix
! In chloroplasts, protons are pumped into the thylakoid space and drive ATP synthesis as they diffuse back into the stroma
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Figure 10.17
MITOCHONDRION STRUCTURE
CHLOROPLAST STRUCTURE
Thylakoid membrane
Stroma
ATP
Thylakoid space
Inter- membrane
space
Inner membrane
Matrix Key
Diffusion
Electron transport
chain
ATP synthase
ADP + H+
H+
Higher [H+] Lower [H+]
P i
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! ATP and NADPH are produced on the side facing the stroma, where the Calvin cycle takes place!
! In summary, light reactions generate ATP and increase the potential energy of electrons by moving them from H2O to NADPH
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Figure 10.18
Photosystem II Photosystem I Cytochrome complex
Light
Pq
Light 4 H+
+2 H+ 4 H+ O2
H2O
Pc
Fd 3
2 1
NADP+
To Calvin Cycle
NADP+ reductase
STROMA (low H+ concentration)
ATP synthase
THYLAKOID SPACE (high H+ concentration)
Thylakoid membrane
ADP +
H+ ATP P i
e- e-
NADPH
½
+ H+
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Figure 10.18a
STROMA (low H+ concentration)
ATP ADP!
ATP synthase
P i
+!H+!
THYLAKOID SPACE (high H+ concentration)
4 H+
Cytochrome complex
Light Photosystem I
Pc
Pq
4 H+
Light
Photosystem II 4 H+
Pc
Fd
Thylakoid membrane
+2 H+
H2O O2 ½
e- e- 2 1
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Figure 10.18b
Cytochrome complex
Light Photosystem I
Pc
Pq
Fd
NADP+!
reductase
NADP+ + H+
NADPH
To Calvin Cycle
STROMA (low H+ concentration)
ATP ADP!
ATP synthase
P i
+!H+!
THYLAKOID SPACE (high H+ concentration) 4 H+
2
3
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Concept 10.3: The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar ! The Calvin cycle, like the citric acid cycle,
regenerates its starting material after molecules enter and leave the cycle
! The cycle builds sugar from smaller molecules by using ATP and the reducing power of electrons carried by NADPH
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! Carbon enters the cycle as CO2 and leaves as a sugar named glyceraldehyde 3-phospate (G3P)
! For net synthesis of 1 G3P, the cycle must take place three times, fixing 3 molecules of CO2
! The Calvin cycle has three phases 1. Carbon fixation (catalyzed by rubisco) 2. Reduction 3. Regeneration of the CO2 acceptor (RuBP)
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Figure 10.UN03
Light
H2O CO2
O2
LIGHT REACTIONS
CALVIN CYCLE
ATP
NADPH
ADP NADP+!
[CH2O] (sugar) 92
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Figure 10.19-1 Input 3 CO2, entering one per cycle
Phase 1: Carbon fixation Rubisco
3-Phosphoglycerate
Calvin Cycle
RuBP P P 3
P 3 P
P 6
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Figure 10.19-2 Input 3 CO2, entering one per cycle
Phase 1: Carbon fixation Rubisco
3-Phosphoglycerate
1,3-Bisphosphoglycerate
Phase 2: Reduction
G3P
Calvin Cycle
RuBP P P 3
P 3 P
P 6
6
6 ADP
P 6 P
ATP
P 6
6
6 NADP+!
6 P i
G3P P 1
Output
Glucose and other organic compounds
NADPH
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Figure 10.19-3 Input 3 CO2, entering one per cycle
Phase 1: Carbon fixation Rubisco
3-Phosphoglycerate
1,3-Bisphosphoglycerate
Phase 2: Reduction
G3P
Calvin Cycle
G3P
Phase 3: Regeneration of RuBP
ATP
3 ADP
3
5 P
RuBP P P 3
P 3 P
P 6
6
6 ADP
P 6 P
ATP
P 6
6
6 NADP+!
6 P i
G3P P 1
Output
Glucose and other organic compounds
NADPH
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Concept 10.4: Alternative mechanisms of carbon fixation have evolved in hot, arid climates ! Dehydration is a problem for plants, sometimes
requiring trade-offs with other metabolic processes, especially photosynthesis
! On hot, dry days, plants close stomata, which conserves H2O but also limits photosynthesis
! The closing of stomata reduces access to CO2 and causes O2 to build up
! These conditions favor an apparently wasteful process called photorespiration 96
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Photorespiration: An Evolutionary Relic?
! In most plants (C3 plants), initial fixation of CO2, via rubisco, forms a three-carbon compound (3-phosphoglycerate)
! In photorespiration, rubisco adds O2 instead of CO2 in the Calvin cycle, producing a two-carbon compound
! Photorespiration consumes O2 and organic fuel and releases CO2 without producing ATP or sugar
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! Photorespiration may be an evolutionary relic because rubisco first evolved at a time when the atmosphere had far less O2 and more CO2
! Photorespiration limits damaging products of light reactions that build up in the absence of the Calvin cycle
! In many plants, photorespiration is a problem because on a hot, dry day it can drain as much as 50% of the carbon fixed by the Calvin cycle
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C4 Plants
! C4 plants minimize the cost of photorespiration by incorporating CO2 into four-carbon compounds
! There are two distinct types of cells in the leaves of C4 plants:
! Bundle-sheath cells are arranged in tightly packed sheaths around the veins of the leaf
! Mesophyll cells are loosely packed between the bundle sheath and the leaf surface
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! Sugar production in C4 plants occurs in a three-step process:
1. The production of the four carbon precursors is catalyzed by the enzyme PEP carboxylase in the mesophyll cells
! PEP carboxylase has a higher affinity for CO2 than rubisco does; it can fix CO2 even when CO2 concentrations are low
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2. These four-carbon compounds are exported to bundle-sheath cells
3. Within the bundle-sheath cells, they release CO2 that is then used in the Calvin cycle
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Figure 10.20
Mesophyll cell
Bundle- sheath cell
Photo- synthetic cells of C4 plant leaf
Vein (vascular tissue)
C4 leaf anatomy
Stoma
The C4 pathway
Mesophyll cell PEP carboxylase
Oxaloacetate (4C)
Malate (4C)
Pyruvate (3C)
CO2
ADP
PEP (3C)
ATP
CO2
Calvin Cycle
Bundle- sheath cell
Sugar
Vascular tissue
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Figure 10.20a
Mesophyll cell
Bundle- sheath cell
Photo- synthetic cells of C4 plant leaf
Vein (vascular tissue)
C4 leaf anatomy
Stoma
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Figure 10.20b The C4 pathway
Mesophyll cell PEP carboxylase
Oxaloacetate (4C)
Malate (4C)
Pyruvate (3C)
CO2
ADP
PEP (3C)
ATP
CO2
Calvin Cycle
Bundle- sheath cell
Sugar
Vascular tissue 104
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! Since the Industrial Revolution in the 1800s, CO2 levels have risen greatly
! Increasing levels of CO2 may affect C3 and C4 plants differently, perhaps changing the relative abundance of these species
! The effects of such changes are unpredictable and a cause for concern
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CAM Plants
! Some plants, including succulents, use crassulacean acid metabolism (CAM) to fix carbon
! CAM plants open their stomata at night, incorporating CO2 into organic acids
! Stomata close during the day, and CO2 is released from organic acids and used in the Calvin cycle
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Figure 10.21
Sugarcane Pineapple
C4 CO2 CO2 CAM
Organic acid
Organic acid
Night
Day
CO2 CO2
Calvin Cycle
Calvin Cycle
Sugar Sugar
Bundle- sheath cell
(a) Spatial separation of steps
(b) Temporal separation of steps
Mesophyll cell
2
1 1
2
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Figure 10.21a
Sugarcane
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Figure 10.21b
Pineapple
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The Importance of Photosynthesis: A Review
! The energy entering chloroplasts as sunlight gets stored as chemical energy in organic compounds
! Sugar made in the chloroplasts supplies chemical energy and carbon skeletons to synthesize the organic molecules of cells
! Plants store excess sugar as starch in structures such as roots, tubers, seeds, and fruits
! In addition to food production, photosynthesis produces the O2 in our atmosphere
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Figure 10.22a
O2 CO2
H2O
Sucrose (export)
H2O
Light
LIGHT REACTIONS:
Photosystem II Electron transport
chain Photosystem I
Electron transport chain
Chloroplast
NADP+!
ADP!
+!P!
i!
NADPH!
ATP!
RuBP!
G3P!
CALVIN CYCLE !
Starch (storage)!
3-Phosphoglycerate!
Sucrose (export)!O2 H2O
Mesophyll cell
CO2
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Figure 10.22b
LIGHT REACTIONS CALVIN CYCLE 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
• 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
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Figure 10.23
Flow of Genetic Information in the Cell: DNA → RNA → Protein (Chapters 5–7)
Movement Across Cell Membranes (Chapter 7)
Energy Transformations in the Cell: Photosynthesis and Cellular Respiration (Chapters 8–10)
DNA
mRNA Nucleus
Nuclear pore
Protein
Ribosome mRNA
Protein in vesicle
Rough endoplasmic reticulum (ER)
Vesicle forming Golgi
apparatus Protein
Plasma membrane
Cell wall
Photosynthesis in chloroplast
Organic molecules
Transport pump
Cellular respiration in mitochondrion
ATP
ATP
ATP
ATP
CO2
H2O
H2O
CO2
O2
O2 5
4
3
2
1
7
8
Vacuole
9 10
11
6
MAKE CONNECTIONS The Working Cell
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Figure 10.23a
Flow of Genetic Information in the Cell: DNA → RNA → Protein (Chapters 5–7)
DNA
mRNA Nucleus
mRNA
Nuclear pore
Protein Protein in vesicle
Rough endoplasmic reticulum (ER)
Ribosome
1
2
3
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Figure 10.23b
Plasma membrane
4
Golgi apparatus
Vesicle forming
Protein
Cell wall
Flow of Genetic Information in the Cell: DNA → RNA → Protein (Chapters 5–7)
5
6
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Figure 10.23c
Photosynthesis in chloroplast
Organic molecules
Cellular respiration in mitochondrion
Transport pump
Movement Across Cell Membranes (Chapter 7)
Energy Transformations in the Cell: Photosynthesis and Cellular Respiration (Chapters 8–10)
O2
O2
H2O
CO2
CO2
H2O
ATP
ATP
ATP
ATP
7
8
11
10 9
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Figure 10.UN04a
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Figure 10.UN04b
Corn plant surrounded by invasive velvetleaf plants 118
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Figure 10.UN05
Primary acceptor
Primary acceptor
Pq
Cytochrome complex
Photosystem II Photosystem I
Pc
Fd
NADPH
NADP+!
+ H+!NADP+!
reductase!H2O
O2
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Figure 10.UN06
Regeneration of CO2 acceptor
Calvin Cycle
Carbon fixation
Reduction
1 G3P (3C)
5 x 3C
3 x 5C 6 x 3C
3 CO2
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Figure 10.UN07
pH 7
pH 4
pH 4
pH 8
ATP
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Figure 10.UN08
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