Reece •Urry• Cain • Wasserman •Minorsky• Jackson ... 10 - Photosynthesis.pdf · Photosynthesis 10 Photosynthesis 10 +! + +!!

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


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

2


!  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

3


Figure 10.1

4


Figure 10.1a

Other organisms also benefit from photosynthesis.

5


!  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

6


Figure 10.2

(a) Plants

(b) Multicellular alga

(c) Unicellular eukaryotes

(d) Cyanobacteria

(e) Purple sulfur bacteria

40 µm

1 µm

10 µ

m

7


Figure 10.2a

(a) Plants

8


Figure 10.2b

(b) Multicellular alga

9


Figure 10.2c

(c) Unicellular eukaryotes 10 µ

m

10


Figure 10.2d

(d) Cyanobacteria 40 µm

11


Figure 10.2e

1 µm

(e) Purple sulfur bacteria

12


!  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

13


!  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

14


Figure 10.3

15


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

16


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

17


!  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

18


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

19


Figure 10.4a Leaf cross section

Stomata

Chloroplast

Mesophyll

Chloroplasts Vein

Mesophyll cell

20 µm

CO2 O2

20


Figure 10.4b

Chloroplast

Stroma Granum

Thylakoid Thylakoid space

Outer membrane

Intermembrane space Inner membrane

1 µm

21


Figure 10.4c

Stroma Granum

1 µm

22


Figure 10.4d

20 µm

Mesophyll cell

23


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

24


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

25


Figure 10.5

Reactants:

Products:

6 CO2 12 H2O

C6H12O6 6 H2O 6 O2

26


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

27


Figure 10.UN01

becomes reduced

becomes oxidized

28


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


!  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

30


Figure 10.6-1

Light

Thylakoid Stroma

Chloroplast

LIGHT REACTIONS

NADP+

ADP

P i +!

H2O

31


Figure 10.6-2

Light

Thylakoid Stroma

Chloroplast

LIGHT REACTIONS

NADP+

ADP

P i +!

H2O

NADPH

ATP

O2

32


Figure 10.6-3

Light

Thylakoid Stroma

Chloroplast

LIGHT REACTIONS

NADP+

ADP

P i +!

H2O

O2

CO2

NADPH

ATP

CALVIN CYCLE

33


Figure 10.6-4

Light

Thylakoid Stroma

Chloroplast

LIGHT REACTIONS

NADP+

ADP

P i +!

H2O

[CH2O] (sugar)

CALVIN CYCLE

CO2

NADPH

ATP

O2

34


BioFlix: The Carbon Cycle

35


BioFlix: Photosynthesis

36


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

37


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

38


!  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

39


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

40


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

41


Figure 10.8

Light

Chloroplast

Reflected light

Granum

Transmitted light

Absorbed light

42


Animation: Light and Pigments

43


!  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

44


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

45


!  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

46


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

47


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

48


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

49


Figure 10.10c

400 500 600 700 (c) Engelmann’s experiment

Aerobic bacteria

Filament of alga

50


!  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

51


!  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

52


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

53


Video: Space-Filling Model of Chlorophyll a

54


!  Accessory pigments called carotenoids function in photoprotection; they absorb excessive light that would damage chlorophyll

55


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

56


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−

57


Figure 10.12a

(b) Fluorescence 58


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

59


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 chlorophyll a molecules

THYLAKOID SPACE (INTERIOR OF THYLAKOID)

Thyl

akoi

d m

embr

ane

e−

60


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 chlorophyll a molecules

THYLAKOID SPACE (INTERIOR OF THYLAKOID)

Thyl

akoi

d m

embr

ane

e−

61


Figure 10.13b

(b) Structure of a photosystem

Chlorophyll STROMA

THYLA- KOID SPACE

Protein subunits

Thyl

akoi

d m

embr

ane

62


!  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

63


!  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

64


!  Photosystem I (PS I) is best at absorbing a wavelength of 700 nm

!  The reaction-center chlorophyll a of PS I is called P700

65


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

66


!  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+)

67


Figure 10.UN02

Light

H2O CO2

O2

LIGHT REACTIONS

CALVIN CYCLE

ATP

NADPH

ADP NADP+!

[CH2O] (sugar) 68


Figure 10.14-1

Pigment molecules

e−

1

2

P680 Light

Photosystem II!(PS II)

Primary acceptor

69


Figure 10.14-2

Pigment molecules

e−

1

2

P680 Light


Primary acceptor

3e− e−

2 H+!

+!O2!

H2O!

½

70


Figure 10.14-3

Pigment molecules

e−

1

2

P680 Light


Primary acceptor

3e− e−

2 H+!

+!O2!

H2O!

ATP

4

5

Electron transport chain

Cytochrome complex

Pq

Pc ½

71


Figure 10.14-4

Pigment molecules

e−

1

2

P680 Light


Primary acceptor

3e− e−

2 H+!

+!O2!

H2O!

ATP

4

5


Cytochrome complex

Pq

Pc P700

Light

Photosystem I!(PS I)

6

Primary acceptor

e−

½

72


Figure 10.14-5

Pigment molecules

e−

1

2

P680 Light


Primary acceptor

3e− e−

2 H+!

+!O2!

H2O!

ATP

4

5


Cytochrome complex

Pq

Pc P700

Light

Photosystem I!(PS I)

6

Primary acceptor

e− e−

7

8Fd

e−


NADP+!

reductase NADPH

NADP+!

+ H+!

½

73


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

74


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

75


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

76


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

77


!  The energy changes of electrons during linear flow through the light reactions can be shown in a mechanical analogy

78


Figure 10.15

Mill makes

ATP NADPH

Phot

on

Photosystem II! Photosystem I!

ATP

Phot

on

e−

e−

e− e−

e−

e−

e−

79


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

80


Figure 10.16

Primary acceptor

Primary acceptor

Fd

Cytochrome complex

Pc

Pq

Photosystem II!Photosystem I!

Fd NADP+!

+ H+!NADP+!

reductase

NADPH!

ATP

81


!  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

82


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

83


!  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

84


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

85


!  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

86


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+

87


Figure 10.18a


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

88


Figure 10.18b

Cytochrome complex

Light Photosystem I

Pc

Pq

Fd

NADP+!

reductase

NADP+ + H+

NADPH

To Calvin Cycle


ATP ADP!

ATP synthase

P i

+!H+!

THYLAKOID SPACE (high H+ concentration) 4 H+

2

3

89


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

90


!  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)

91


Figure 10.UN03

Light

H2O CO2

O2

LIGHT REACTIONS

CALVIN CYCLE

ATP

NADPH

ADP NADP+!

[CH2O] (sugar) 92


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

93




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

94




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

95


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


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

97


!  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

98


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

99


!  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

100


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

101


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

102


Figure 10.20a

Mesophyll cell

Bundle- sheath cell

Photo- synthetic cells of C4 plant leaf

Vein (vascular tissue)

C4 leaf anatomy

Stoma

103


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


!  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

105


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

106


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

107


Figure 10.21a

Sugarcane

108


Figure 10.21b

Pineapple

109


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

110


Figure 10.22a

O2 CO2

H2O

Sucrose (export)

H2O

Light

LIGHT REACTIONS:

Photosystem II Electron transport

chain Photosystem I


Chloroplast

NADP+!

ADP!

+!P!

i!

NADPH!

ATP!

RuBP!

G3P!

CALVIN CYCLE !

Starch (storage)!

3-Phosphoglycerate!

Sucrose (export)!O2 H2O

Mesophyll cell

CO2

111


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

112


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

113


Figure 10.23a


DNA

mRNA Nucleus

mRNA

Nuclear pore

Protein Protein in vesicle

Rough endoplasmic reticulum (ER)

Ribosome

1

2

3

114


Figure 10.23b

Plasma membrane

4

Golgi apparatus

Vesicle forming

Protein

Cell wall


5

6

115


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

116


Figure 10.UN04a

117


Figure 10.UN04b

Corn plant surrounded by invasive velvetleaf plants 118


Figure 10.UN05

Primary acceptor

Primary acceptor

Pq

Cytochrome complex

Photosystem II Photosystem I

Pc

Fd

NADPH

NADP+!

+ H+!NADP+!

reductase!H2O

O2

119


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

120


Figure 10.UN07

pH 7

pH 4

pH 4

pH 8

ATP

121


Figure 10.UN08

122

Documents

Reece •Urry• Cain • Wasserman •Minorsky• Jackson ... 10 - Photosynthesis.pdf · Photosynthesis 10 Photosynthesis 10 +! + +!!