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BAGIAN 2
FOTOSINTESIS:Penggunaan sinar untukpembentukan makanan
SUGENG SETYO UTOMOSMA NEGERI 2 LUMAJANG
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Light is central to the life of a plant
Photosynthesis is the most important chemical processon Earth
It provides food for
virtually all organisms Plant cells convert light
into chemical signalsthat affect a plantslife cycle
2.1 Life in the Sun
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Light can influencethe architecture of a
plant
Too much sunlightcandamage a plant
Chloroplasts andcarotenoidshelp to preventsuch damage
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Photosynthesis is the process by which autotrophic
organisms use light energy to make sugar andoxygen gas from carbon dioxide and water
AN OVERVIEW OF PHOTOSYNTHESIS
Carbondioxide Water Glucose
OxygengasPHOTOSYNTHESIS
Plants, some protists, and some bacteria are
photosynthetic autotrophs.
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On land, plants such as oak trees and cacti are thepredominant producers
Figure 2.1A Figure 2.1B
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In aquatic environments, algae and photosyntheticbacteria are the main food producers
Figure 2.1 C Figure 2.1 D Figure 2.1 E
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In most plants, photosynthesis occurs primarilyin the leaves, in the chloroplasts
A chloroplast contains:
stroma, a fluid
grana, stacks of thylakoids
The thylakoids contain chlorophyll
Chlorophyll is the green pigment that captureslight for photosynthesis
2.2 Photosynthesis occurs in chloroplasts
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The location and structure of chloroplasts
Figure 2.2
LEAF CROSS SECTION MESOPHYLL CELL
LEAF
Chloroplast
Mesophyll
CHLOROPLAST Intermembrane space
Outermembrane
Innermembrane
ThylakoidcompartmentThylakoid
Stroma
Granum
StromaGrana
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Figure 2.2 A
Figure 2.2 B
Experiment 1
Experiment 2
Notlabeled
Labeled
Reactants:
Products:
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Water molecules are split apart and electronsand H+ions are removed, leaving O2gas
These electrons and H+ions are transferred toCO2, producing sugar
2.3 Photosynthesis is a redox process, as is cellularrespiration
Figure 2.3 A
Figure 2.3 B
Reduction
Oxidation
Oxidation
Reduction
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Light
Chloroplast
LIGHTREACTIONS
(in grana)
CALVINCYCLE
(in stroma)
H2O
O2
CO2
NADP+
ADP+ P
Sugar
ATP
NADPH
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2.5 Visible radiation drives the light reactions
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Copyright 2003 Pearson Education, Inc. publishing as Benjamin CummingsFigure 2.5
Light
Chloroplast
Reflected
light
Absorbed
light
Transmittedlight
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Fluorescence of isolated chlorophyll in solution
Figure 2.5 A
Heat
Photon
(fluorescence)
Photon
Chlorophyll
molecule
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Figure 2.5 C
Primary
electron acceptor
Photon Reaction centerPHOTOSYSTEM
Pigment
molecules
of antenna
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The electron transport chains are arranged withthe photosystems in the thylakoid membranesand pump H+through that membrane
The flow of H+back through the membrane isharnessed by ATP synthase to make ATP
In the stroma, the H+ions combine with NADP+
to form NADPH
2.6 Chemiosmosis powers ATP synthesis in thelight reactions
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Photosystem II regains electrons by splittingwater, leaving O2gas as a by-product
Figure 2.6
Primaryelectron acceptor
Primaryelectron acceptor
Photons
PHOTOSYSTEM I
PHOTOSYSTEM II
Energy forsynthesis of
by chemiosmosis
h d i f b h i i i
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The production of ATP by chemiosmosis inphotosynthesis
Figure 2.6A
Thylakoidcompartment(high H+)
Thylakoidmembrane
Stroma(low H+)
Light
Antennamolecules
Light
ELECTRON TRANSPORT
CHAIN
PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE
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The Calvin cycle occurs inthe chloroplasts stroma
This is where carbonfixation takes place andsugar is manufactured
2.7 ATP and NADPH power sugar synthesis in theCalvin cycle
CALVIN CYCLE: CONVERTING CO2TO SUGARS
INPUT
Figure 7.10AOUTPUT:
CALVIN
CYCLE
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The Calvin cycle constructs G3P using
carbon from atmospheric CO2
electrons and H+from NADPH
energy from ATP
Energy-rich sugar is then converted intoglucose
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Many plants make more sugar than they need
The excess is stored in roots, tuber, and fruits
These are a major source of food for animals
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Most plants are C3plants, which take CO2directly from the air and use it in the Calvincycle
In these types of plants, stomata on the leafsurface close when the weather is hot
This causes a drop in CO2and an increase in
O2in the leaf
Photorespiration may then occur
2.8 C4and CAM plants have special adaptationsthat save water
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Photorespiration in a C3plant
CALVIN
CYCLE
2-C compound
Figure 2.8C
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Some plants have special adaptationsthat enable them to save water
CALVIN
CYCLE
4-C compound
Special cells in C4plantscorn andsugarcaneincorporateCO2into a four-carbon
molecule
This molecule can thendonate CO2to the
Calvin cycle
3-C sugarFigure 2.8A
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The CAM plantspineapples, most
cacti, and succulentsemploy a differentmechanism
CALVIN
CYCLE
4-C compound
Figure 2.8B
They open theirstomata at night andmake a four-carboncompound
It is used as a CO2source by the samecell during the day
3-C sugar
Night
Day
PHOTOSYNTHESIS SOLAR RADIATION AND
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Due to the increased burning of fossil fuels,atmospheric CO2is increasing
CO2warms Earths surface by trapping heat inthe atmosphere
This is called the greenhouse effect
2.9 Human activity is causing global warming;
photosynthesis moderates it
PHOTOSYNTHESIS, SOLAR RADIATION, ANDEARTHS ATMOSPHERE
Unfortunately, deforestation may cause a
decline in global photosynthesis
Because photosynthesis removes CO2from theatmosphere, it moderates the greenhouse effect
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Figure 2.9
Sunlight
ATMOSPHERE
Radiant heat
trapped by CO2
and other gases
2 buah Kontrol
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2 buah Kontrol
Kontrol suhu tinggi (air panas)
Kontrol suhu rendah (es)
Kontrol pH asam
Kontrol pH basa
Kontrol CO2 tinggi (NaHCO3)
Kontrol i.c. rendah (teduh)
Kontrol i.c. dg. mika kuning
Kontrol i.c. dg. mika hijau
Kontrol i.c. dg. mika merah
Kontrol kecerahan air