7. Photosynthesis. Key Terms C3plantsC3 식물 C4plantsC4 식물 Calvin cycle 캘빈회로 ...

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

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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

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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

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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.

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• 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.

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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

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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