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77. . PhotosynthesisPhotosynthesis
Key Terms
C3plants C3 식물 C4plants C4 식물 Calvin cycle 캘빈회로 CAM plants (crassulacean acid metabolism)
다육식물유기산대사 식물 chlorophyll a 엽록소 a chloroplast 엽록체 electromagnetic spectrum
전자기스펙트럼
global warming 지구온난화 grana 그라나 greenhouse effect 온실효과 greenhouse gases 온실가스
light reaction 명반응 NADPH 환원 니코틴아미드 아데닌 디뉴클레오티드 인산 photon 광자 photosystem 광계 primary electron acceptor
1차전자수용체
reaction center 반응중심 stoma(ta) 기공 stroma 스트로마 thylakoids
틸라코이드 vein 잎맥 wavelength 파장
Word Roots
chloro = green; plast= formed or molded (chloroplast: the organelle of photosynthesis)
electro = electricity; magne= magnetic (electromagnetic spectrum: the full range of radiation)
photo = light (photosystem: cluster of pigment molecules) phyll = leaf (chlorophyll: photosynthetic pigment in chloroplasts) stoma = mouth (stomata: tiny pores in leaves through which gases
are exchanged) thylac = a sac or pouch (thylakoids: membranous sacs suspended
in the stroma)
Impacts, Issues:Biofuels Coal, petroleum, and natural gas were once
ancient forests, a limited resource; biofuels from wastes are a renewable resource
Key concepts
The rainbow catchers Making ATP and NADPH Making sugars Evolution and Photosynthesis Photosynthesis, CO2, and global warming
Linked ProcessesLinked Processes
Photosynthesis Energy-storing pathway
Releases oxygen
Requires carbon dioxide
Aerobic RespirationAerobic Respiration Energy-releasing pathwayEnergy-releasing pathway
Requires oxygenRequires oxygen
Releases carbon dioxideReleases carbon dioxide
Sunlight
Heat
PhotosynthesisCellular
respiration
The Process of Science: Chronology of Photosynthesis
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
1648 van Helmont 5 lb willow 164 lb over 5 years period with rain water
1772 Joseph Priestley Plant replenishes the O2.
1778 Ingen-Housz Priestley’s effect occurred only when the plant was illuminated.
Jean Senebier The growth of plant is an increase in carbon content.
CO2 + H2O (CH2O) + O2
1883 Theodor W. Engelmann German biologist
– Performed an experiment using bacteria and algae and determined that certain types of light drive photosynthesis.
The Process of Science:
F. F. Blackman Photosynthesis involve two quite distinct processes.
- by using Elodea, an aquatic plant and by counting the rate of oxygen bubbles.
Calvin The Dark reactions
- using 14CO2 and two-dimensional paper chromatography
Van Niel The Light reactions
– purple sulfur bacteria CO2 + 2 H2S (CH2O) + H2O + S2
CO2 + 2 H2O (CH2O) + H2O + O2
1941 Samuel Ruben
– 18O-CO2 , 18O-H2O Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Figure 7.6
action spectrum
7.1 What Colors of Light Drive Photosynthesis?
Engelmann’s exp., 1883
Fig. 7-1, p.106
Sunlight and SurvivalSunlight and Survival
7.1 Sunlight as an Energy Source
Photosynthetic organisms use pigments to capture the energy of sunlight
Photosynthesis ( 광합성 )• The synthesis of organic molecules from
inorganic molecules using the energy of light
shortest wavelengths
(most energetic)
range of most radiationreaching Earth’s surface
gamma rays
range of heat escapingfrom Earth’s surface
longest wavelengths
(lowest energy)x
raysultravioletradiation
near-infraredradiation
infraredradiation microwaves radio
waves
VISIBLE LIGHT
Wavelengths of light (nanometers)
Fig. 7-2, p.108
Visible Light
400 450 500 550 600 650 700
The Nature of Sunlight Sunlight is a type of energy called radiation, or
electromagnetic energy.
Photons
An elementary particle and the basic "unit" of light
Packets of light energy Each type of photon has fixed amount of energy Photons having most energy travel as shortest
wavelength (blue-violet light)
Pigments
• An organic molecule that selectively absorbs light of specific wavelengths
Color you see is the wavelengths not absorbed Light-catching part of molecule often has alternating
single and double bonds These bonds contain electrons that are capable of
being moved to higher energy levels by absorbing light
Fig. 7-3a, p.109
Variety of Pigments
Chlorophylls a and b: green, blue
Carotenoids: red ~ yellow
Anthocyanins: red ~ purple
Phycobilins: red or blue-green
Xanthophylls: yellow, brown, blue or purple
Photosynthetic Pigments Chlorophyll a
The most common photosynthetic pigment Absorbs violet and red light (appears green)
Collectively, chlorophyll and accessory pigments absorb most wavelengths of visible light
Certain electrons in pigment molecules absorb photons of light energy, boosting electrons to a higher energy level
Energy is captured and used for photosynthesis
ChlorophyllsW
avel
eng
th a
bso
rpti
on
(%
)
Wavelength (nanometers)
chlorophyll b
chlorophyll a
Main pigments in most phototrophs
chl b
- COO-
Accessory PigmentsAccessory Pigmentsp
erce
nt
of
wav
elen
gth
s ab
sorb
ed
wavelengths (nanometers)
beta-carotenephycoerythrin (a phycobilin)
Carotenoids, Phycobilins, Anthocyanins
β-carotene
시아노박테리아홍조류
Absorption maximum of rhodopsin is 500nm, blue-green light.
(vitamin A )
Pigments in Photosynthesis
Bacteria Pigments in plasma membranes
Plants Pigments and proteins organized into photosystems
that are embedded in thylakoid membrane system
7.2 Exploring the Rainbow
Engelmann identified colors of light that drive photosynthesis (violet and red) by using a prism to divide light into colors
Algae using these wavelengths gave off the most oxygen
An absorption spectrum shows which wavelengths a pigment absorbs best
Organisms in different environments use different pigments
T.E. Englemann’s Experiment
Background
Certain bacterial cells will move toward places
where oxygen concentration is high
Photosynthesis produces oxygen
a strand of green alga, Chladophora.
T.E. Englemann’s Experiment
action spectrum
색소의 광흡수율
Fig. 7-4c, p. 110
phycoerythrobilin100 chlorophyll b
phycocyanobilin
80β-carotene
chlorophyll a
60
40
20
Lig
ht
abso
rpti
on
(%
)
0
Wavelength (nanometers)
C Absorption spectra of a few photosynthetic pigments. Line color indicates the characteristic color of each pigment.
400400 500500 600600 700700
7.3 Overview of Photosynthesis Photosynthesis Equation
12H2O + 6CO2 6O2 + C2H12O6 + 6H2OWater Carbon
DioxideOxygen Glucose Water
LIGHT ENERGY
In-text figurePage 111
Fig. 7-6a, p.111
Photosynthesis
stroma
thylakoid compartment
thylakoid membrane system inside stroma
Fig. 7-6b, p.111
two outer membranes
Chloroplast Structure
stroma
(thylakoids connected by channels)
An organelle that specializes in photosynthesis in plants and many protists
7.3 Overview of Photosynthesis
Chloroplast ( 엽록체 ) An organelle that specializes in photosynthesis in plants and
many protists
Stroma A semifluid matrix surrounded by the two outer membranes of
the chloroplast Sugars are built in the stroma
Thylakoid membrane Folded membrane that make up thylakoids Contains clusters of light-harvesting pigments that absorb
photons of different energies
Fig. 7-5c, p. 111
Two Stages of Photosynthesis
Overview of Photosynthesis
Photosystems (type I and type II) Groups of molecules that work as a unit to begin the reactions of
photosynthesis Convert light energy into chemical energy
Light-dependent reactions ( 명반응 ) Light energy is transferred to ATP and NADPH Water molecules are split, releasing O2
Light-independent reactions ( 암반응 , Calvincycle) Energy in ATP and NADPH drives synthesis of glucose and
other carbohydrates from CO2 and water
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
광합성 명반응
12 H2O + 12 NADP+ + 18 ADP +18 Pi
12 NADPH + 12 H+ + 18 ATP + 6 O2
암반응
6 CO2 + 18 ATP + 12 NADPH + 12 H+
C6H12O6 + 12 NADP+ + 18 ADP + 18 Pi + 6 H2O
12 H2O + 6 CO2 C6H12O6 + 6 H2O + 6 O2
6 H2O + 6 CO2 C6H12O6 + 6 O2
In the first stage of photosynthesis, Pigments absorb light energy, give up e-, which enter electron transfer chains
The electrons may be used in a noncyclic or cyclic pathway of ATP formation
ATP and NADPH form, Water molecules split, and Oxygen is released
Pigments that gave up electrons get replacements
7. 4 Light-Dependent Reactions
The Thylakoid Membrane
Fig. 7-7, p.112
photon
Light-Harvesting Complex
Photosystem
Light-Dependent Reactions
Most pigments in photosystem are harvester pigments
When excited by light energy, these pigments transfer energy to adjacent pigment molecules
Each transfer involves energy loss
Photosystem Function: Reaction Center
Energy is reduced to level that can be captured by molecule of chlorophyll a
This molecule (P700 or P680) is the reaction center of a photosystem
Reaction center accepts energy and donates electron to acceptor molecule
Cyclic and Noncyclic Pathways
Electrons from photosystems take noncyclic or cyclic pathways, forming ATP
to second stage of reactions
The Light-Dependent Reactions of Photosynthesis
ATP synthaselight energy
light energyNADPH ATP
ADP + Piphotosystem II
electron transfer chain
photosystem I
thylakoid compartment
stroma
NADP+
H+ + 2 e
+
NADPHOPO3H2
NADP+
OPO3H
2
NADPH
NADP+
Nicotinamide adenine
dinucleotide phosphate
H2O
Electron Transfer Chain
Adjacent to photosystem Organized arrays of enzymes, coenzymes, and other
proteins that accept and donate electrons in a series
Acceptor molecule receives electrons from reaction center
As electrons pass along chain, energy they release is used to build up a H+ gradient across the membrane
H+ flows through ATP synthase, which attaches a phosphate group to ADP, produce ATP in the stroma.
Noncyclic Electron Flow
photolysis
H2O
NADP+ NADPH
e–
ATP
ATP SYNTHASE
PHOTOSYSTEM IPHOTOSYSTEM II ADP + Pi
e–
first electron transfer chain
second electron transfer chain
Two-step pathway for light absorption and electron excitation Uses two photosystems: type I and type II Produces ATP and NADPH Involves photolysis - splitting of water – producing O2
Electron Flow in a Cyclic Pathway
When NADPH accumulates in the stroma, the noncyclic pathway stalls
A cyclic pathway runs in type I photosystems to make ATP; electrons are cycled back to photosystem I and NADPH does not form
7.5 Energy flow in PhotosynthesisP
ote
nti
al t
o t
ran
sfer
en
erg
y (v
olt
s)
H2O 1/2O2 + 2H+
(Photosystem II)
(Photosystem I)
e– e–
e–e–
secondtransfer
chain
NADPHfirst
transferchain
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• Two types of photosystems cooperate in the light reactions.
Figure 7.11
Ph
oto
n
Ph
oto
n
Water-splittingphotosystem
NADPH-producingphotosystem
ATPmill
• An electron transport chain
– Connects the two photosystems.
– Releases energy that the chloroplast uses to make ATP and NADPH
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
How the Light Reactions ( 명반응 ) Generate ATP and NADPH
2 H + 1/2
Water-splittingphotosystem
Reaction-center
chlorophyll
Light
Primaryelectronacceptor
Energyto make
Electron transport chain
Primaryelectronacceptor
NADPH-producingphotosystem
Light
NADP
1
23
Figure 7.10
광계 I
광계 II
P680
P700Reaction-center
chlorophyll
2e-
Cyclic Electron FlowCyclic Electron Flow Electrons
are donated by P700 in photosystem I to acceptor molecule flow through electron transfer chain and back to P700
Electron flow drives ATP formation No NADPH is formed
electron acceptor
electron transfer chain
e–
e–
e–
e–ATP
Electron flow through transfer chain sets up
conditions for ATP formation at other membrane sites.
H+
P700 appendix VIFig. D
P680
P700
NADPH
ATP빛
산화-
환원
전위
(volt)
-0.6
0
+0.6
광계 II
광계 I
eplastoquinone
ferredoxin
e
순환적 광인산화
Chemiosmotic Model for ATP Formation
ADP + Pi
ATP SYNTHASE
Gradients propel H+ through ATP synthases;ATP forms by phosphate-group transfer
ATP
H+ is shunted across membrane by some components of the first electron transfer chain
PHOTOSYSTEM II
H2Oe–
acceptor
Photolysis in the thylakoid compartment splits water
Chemiosmotic Model of ATP Formation
Electrical and H+ concentration gradients are created between thylakoid compartment and stroma
H+ flows down gradients into stroma through ATP synthesis
Flow of ions drives formation of ATP
Synthesis part of photosynthesis Can proceed in the dark Take place in the stroma Calvin-Benson cycle
Enzyme-mediated reactions that build sugars in the stroma of chloroplasts
7.6 Light-Independent Reactions 암반응
THESE REACTIONS PROCEED IN THE CHLOROPLAST’S
STROMA
Calvin-Benson Cycle
Overall reactants Carbon dioxide
ATP
NADPH
Overall products Glucose
ADP, Pi
NADP+
Reaction pathway is cyclic and RuBP (ribulose bisphosphate) is regenerated
ATP
6 Ru-1,5-BP
phosphorylated glucose
10 PGAL
1 Pi
12 PGA
Calvin-Benson cycle
Fig. 7-10b, p.115
6 ADP
ATP
12 ADP +12 Pi
6CO2
NADPH
12 NADP+
12 PGAL
4 Pi
1
12
12
Calvin- Benson
Cycle
(G3P)
Enzyme rubisco attaches CO2 to RuBP, forms two 3-carbon PGA molecules
appendix VIFig. C
1,3-BPGA
F-1,6-BP
6 Ru-5-P
7.7 Adaptations: Different Carbon-Fixing Pathways
Environments differ, and so do details of photosynthesis
C3 plants C4 plants CAM plants
In Calvin-Benson cycle, the first stable intermediate is a three-carbon PGA (3-phosphoglycerate)
Because the first intermediate has three carbons, the pathway is called the C3 pathway
The C3 Pathway
upperepidermis
palisademesophyll책상엽육조직
spongymesophyll해면엽육조직
lowerepidermis
stoma, 기공 leaf vein, 엽맥 air space
Basswood ( 참피나무 ) leaf, cross-section.
Fig. 7-11a2, p.116
C3 Plants
Photorespiration ( 광호흡 ) in C3 Plants
On hot, dry days stomata close to minimize water loss
Inside leaf Oxygen levels rise Carbon dioxide levels drop
RuBisCO attaches RuBP to O2 instead of CO2
CO2 is produced rather than fixed
Only one PGAL forms instead of two
RuBisCO : Ribulose-1,5-bisphosphate carboxylase oxygenase
Oxygenase activity of RubisCO
RuBP + O2 → Phosphoglycolate + 3-phosphoglycerate + 2H+
3-PGA
PPG
6 PGA + 6 glycolate
6 PGAL
1 PGAL
Twelve turns of the cycle, not just six, to make one 6-carbon sugar
6 RuBP
Calvin-Benson Cycle
CO2
+ water
5 PGAL
Stomata closed: CO2 can’t get in; O2 can’t get out
Rubisco fixes oxygen, not carbon, in mesophyll cells in leaf
Fig. 7-11a3, p.117
Photorespiration in C3 Plants
Fig. 7-13a, p. 117
mesophyll cell
O2CO2
RuBPglycolate
Calvin–Benson Cycle
PGA
sugar ATP NADH
A C3 plants. On dry days, stomata close and oxygen accumulates to high concentration inside leaves. The excess causes rubisco to attach oxygen instead of carbon to RuBP. Cells lose carbon and energy as they make sugars.
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• C3 plants : 벼 , 밀 , 보리 , 귀리 , 콩– Use CO2 directly from the air.
– Are very common and widely distributed.
– RuBP carboxylase has also oxygenase activity.
Water-Saving Adaptations of C4 and CAM Plants
xerophyte : Plants in arid and hot conditions
• C4 plants : 옥수수 , 사탕수수 , 바랭이 , 사탕무우
– Close their stomata to save water during hot and dry weather.
– Can still carry out photosynthesis.
– PEP carboxylase has a high affinity for CO2.
• CAM plants : 파인애플 , 선인장 , 다육식물 ( 돌나물과 , 알로에 등 )
(crassulacean acid metabolism: 다육식물 유기산 대사 )
– Open their stomata only at night to conserve water.
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
기공의 개폐와 수분 보존
• 기공의 열림과 닫힘은 공변세포의 구조와 기능에 의존한다 .
• 공변세포가 삼투에 의하여 세포벽이 바깥쪽으로 팽창할 때 열린다 .
• 공변세포에서 CO2 가 감소되면 ( 광합성은 CO2 의 농도를
감소시킨다 ) K+ 가 흡수되고 팽압이 증가한다 .
• 물이 부족한 상태에서는 ABA( 앱식산 ) 이 증가하면 기공이 닫힌다 .
• 건생 ( 내건성 ) 식물 (xerophyte) –
– 침상 기공과 말아진 잎 (rolled leaf) – 그림 6-6, 67 쪽
– 광합성 과정에서 생리적 적응
upperepidermis
mesophyllcell엽육세포
bundle-sheath cell다발초세포
lowerepidermis
Fig. 7-11b2, p.117
C4 PlantsC4 Plants
옥수수 , 사탕수수 , 사탕무우 , 바랭이 , 대나무
oxaloacetate
malateC4
cycle
pyruvate
CO2
12 PGA
10 PGAL
2 PGAL
1 sugar
RuBP Calvin-Benson
Cycle
Carbon fixed in the mesophyll cell, malate diffuses into adjacent bundle-sheath cell
In bundle-sheath cell, malate gets converted to pyruvate with release of CO2,
which enters Calvin-Benson cycle 12 PGAL
PEP
Stomata closed: CO2 can’t get in; O2 can’t get out
Fig. 7-11b3, p.117
C4 C4 PlantsPlants
PEP carboxylase has a high affinity for CO2.
C4 Plants C4 Plants
Carbon dioxide is fixed twice In mesophyll cells ( 엽육세포 ), carbon dioxide is fixed
to form four-carbon oxaloacetate
Oxaloacetate is transferred to bundle-sheath cells
Carbon dioxide is released and fixed again in Calvin-
Benson cycle
옥수수 , 사탕수수 , 사탕무우 , 바랭이
Fig. 7-11c1, p.117
CAM Plants
• 파인애플 , 선인장 , 다육식물 ( 돌나물과 , 알로에 등 ), 꿩의비름
Fig. 7-11c2, p.117
epidermis with thick cuticle
mesophyll cell
air space
stoma
CAM Plants
CAM PlantsCAM Plants
Carbon is fixed twice (in same cells) Night
• Carbon dioxide is fixed to form organic acids
Day• Carbon dioxide is released and fixed in Calvin-Benson cycle
파인애플 , 선인장 , 다육식물 ( 돌나물과 , 알로에 등 )
phosphoenol pyruvate
oxalate malat
epyruvate
starch glyceraldehyd
e phosphate
CO2
CO2
Calvin cycleglucose
밤 : 기공 열림
낮 : 기공 닫힘
CAM 대사 ( 다육식물 유기산 대사 ) C4 cycle
Stomata stay closed during day, open for CO2 uptake at night only.
C4 CYCLE
Calvin-Benson
Cycle
C4 cycle operates at night when CO2 from aerobic respiration fixed
1 sugar
CO2 that accumulated overnight used in C3 cycle during the day
Fig. 7-11c3, p.117
CAM Plants
C3-C4 comparison
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 7.14
(a) Sugarcane (b) Pineapple
엽육세포
4-C compound
유관속초세포
Calvincycle
Sugar
4-C compound
Calvincycle
Sugar
CAM
Night
Day
C4
CO2 incor-porated intofour-carboncompounds
1
2Four-carboncompoundsrelease CO2to Calvincycle
큰꿩의비름 ,기린초 , 바위솔
돌나물
옥수수 , 사탕수수 사탕무우 바랭이
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Summary of PhotosynthesisSummary of Photosynthesis
Figure 7-14Page 120
light6O2
12H2O
CALVIN-BENSON CYCLE
C6H12O6
(phosphorylated glucose)
NADPHNADP+ATPADP + Pi
PGA PGAL
RuBP
P
6CO2
end product (e.g., sucrose, starch, cellulose)
LIGHT-DEPENDENT REACTIONS
6H2O
LIGHT-INDEPENDENT REACTIONS
Photoautotrophs Carbon source is carbon dioxide
Energy source is sunlight
Heterotrophs Get carbon and energy by eating autotrophs or one another
Chemoautotroph extract energy and carbon from simple molecules, such as
hydrogen sulfide (H2S) and methane.
Plants produce a lot of sugar and release lots of oxygen.
7.8 Photosynthesis and 7.8 Photosynthesis and the Atmosphere the Atmosphere
Photoautotrophs Photoautotrophs
Capture sunlight energy and use it to carry out photosynthesis
Plants
Some bacteria
Many protistans
p.120
12H2O + 6CO2 6O2 + C2H12O6 + 6H2O
Water Carbon Dioxide
Oxygen Glucose Water
light energy
enzymes
the global distribution of photosynthesis, including both oceanic phytoplankton and terrestrial vegetation
Earth With and Without Oxygen Atmosphere
O2 build-up in the Earth's atmosphere
Red and green lines represent the range of the estimates while time is measured in billions of years ago (Ga).Stage 1 (3.85–2.45 Ga): Practically no O2 in the atmosphere.Stage 2 (2.45–1.85 Ga): O2 produced, but absorbed in oceans & seabed rock.Stage 3 (1.85–0.85 Ga): O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer.Stages 4 & 5 (0.85–0.54 Ga) & (0.54 Ga–present): O2 sinks filled, the gas accumulates
Great Oxygenation Event biological diversification
mass extinctionsCambrian explosion
Carboniferous period
Photosynthesis and Evolution
The evolution of noncyclic photophosphorylation dramatically changed the O2 content of Earth’s atmosphere.
Most early cells became extinct because of O2 toxicity.
Selection pressure on evolution of life
In some organisms new pathways that detoxified the oxygen, by-product of photosynthesis evolved and survived the change.
Development of ATP-forming reactions Aerobic respiration
After the ozone layer formed and protect from the UV. organisms could live out in the open.
Fossil Fuel Emissions
7.9 A Burning Concern
Earth’s natural atmospheric cycle of CO2 is out of
balance, mainly as a result of human activity
Photosynthesis locks CO2 from the atmosphere in organic molecules; aerobic respiration returns CO2 to the atmosphere
A balanced cycle of the biosphere
Humans burn wood and fossil fuels for energy, releasing locked carbon into the atmosphere
Contributes to global warming, disrupting biological systems
Concomitant increase of global temperatures and atmospheric CO2
Does the increase of atmospheric CO2 elevate the global temperatures or vice versa?
sunlight
Calvin-Benson
cycle
Light-DependentReactions
end products (e.g., sucrose, starch, cellulose)
ATP
12 PGAL
Light-Independent
Reactions
phosphorylated glucose
6H2O
6 RuBP
12H2O 6O2
NADPH NADP+
6CO2
ADP + Pi
Fig. 7-14, p.120
Fig. 7-15, p.121
Fig. 7-16a, p.121
Fig. 7-16b, p.121