Metabolisme sel (fotosintesis)
Transcript of Metabolisme sel (fotosintesis)
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METABOLISME SELFOTOSINTESIS
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Mesofil
Potongan melintang daun
kloroplas Ikatan pembuluh
Stomata
Kloroplas Sel mesofil
CO2 O2
20 m
Figure 10.4a
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Membranluar
Ruangintermembran
Membrandalam
1 m
Ronggatilakoid
TilakoidGranumStroma
KloroplasFigure 10.4b
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cahaya
Reaksiterang
Kloroplas
NADP
ADP
+ P i
H2O
Figure 10.6-1
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cahaya
Reaksiterang
Kloroplas
ATP
NADPH
NADP
ADP
+ P i
H2O
O2
Figure 10.6-2
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Cahaya
Reaksiterang
SiklusCalvin
Kloroplas
ATP
NADPH
NADP
ADP
+ P i
H2O CO2
O2
Figure 10.6-3
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Cahaya
Reaksiterang
SiklusCalvin
Kloroplas
[CH2O](gula)
ATP
NADPH
NADP
ADP
+ P i
H2O CO2
O2
Figure 10.6-4
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Reaksi terang• Terjadi pada Grana Tilakoid
• Membutuhkan cahaya matahari akan terpecah menjadi spektrum warna
• Percobaan Engelmann pada thn 1883 menggunakan Spirogyra (ganggang hijau fotosintetik) membuktikan bahwa cahaya yang diserap oleh klorofil (pigmen fotosintetik) adalah spektrum merah dan nila
• Pigmen fotosintetik pada tumbuhan klorofil -a dan klorofil -b serta karotenoid
• Terdapat 2 fotosistem fotosistem 1 (PS1, pusat reaksi P700) dan fotosistem 2 (PS2, pusat reaksi P680)
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(b) Spektrum aksi
(a) Spektrumpeneyerapan
PercobaanEngelmann
(c)
klorofill a
klorofil b
karotenoid
Wavelength of light (nm)
Ab
sorp
tion
of lig
ht b
ych
loro
pla
st pig
men
tsR
ate o
f ph
oto
syn
thesis
(mea
sured
by
O2
release)
Bakteri aerob
FilamenAlga (Spirogyra)
400 500 600 700
400 500 600 700
400 500 600 700
RESULTSFigure 10.10
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Figure 10.11
Hydrocarbon tail(H atoms not shown)
Porphyrin ring
CH3
CH3 in chlorophyll a
CHO in chlorophyll b
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Figure 10.14-5
Cytochromecomplex
Primaryacceptor
Primaryacceptor
H2O
O2
2 H
+1/2
P680
Light
Pigmentmolecules
Photosystem II(PS II)
Photosystem I(PS I)
Pq
Pc
ATP
1
2
3
5
6
7
8
P700
Light
+ HNADP
NADPH
NADP
reductase
Fd
e
e
ee
4
e
e
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Menghasilkan NADPH, ATP, dan oksigen
Nonsiklik
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Aliran siklik– Hanya fotosistem I yang digunakan
– Hanya ATP yang dihasilkan
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Figure 10.18
STROMA(low H concentration)
STROMA(low H concentration)
THYLAKOID SPACE(high H concentration)
Light
Photosystem II
Cytochromecomplex
Photosystem ILight
NADP
reductase
NADP + H
ToCalvinCycle
ATPsynthase
Thylakoidmembrane
2
1
3
NADPH
Fd
Pc
Pq
4 H+
4 H++2 H+
H+
ADP
+
P i
ATP
1/2
H2OO2
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Reaksi Gelap
• Hasil reaksi terang ATP dan NADPH dibawa ke STROMA (matriks kloroplas) dan masuk dalam reaksi GELAP/siklus Calvin-Benson
• Reaksi gelap mengubah CO2 menjadi glukosa (C6H12O6)
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Input
3 (Entering oneat a time)
CO2
Phase 1: Carbon fixation
Rubisco
3 P P
P6
Short-livedintermediate
3-Phosphoglycerate6
6 ADP
ATP
6 P P
1,3-Bisphosphoglycerate
CalvinCycle
6 NADPH
6 NADP
6 P i
6 P
Phase 2: Reduction
Glyceraldehyde 3-phosphate(G3P)
P5
G3P
ATP
3 ADP
Phase 3:Regeneration ofthe CO2 acceptor(RuBP)
3 P P
Ribulose bisphosphate(RuBP)
1 P
G3P(a sugar)
Output
Glucose andother organiccompounds
3
Figure 10.19-3
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Fotorespirasi • CO2 masuk ke daun melalui celah daun (stomata), ketika suhu siang hari sangat panas, stomata akan menutup untuk mengurangi resiko kehilangan air (H2O) melalui transpirasi akibatnya pasokan CO2 berkurang yg masuk ke reaksi gelap bukan CO2 melainkan O2 (hasil fotolisis air pada saat reaksi terang) TIDAK DIHASILKAN GULA FOTORESPIRASI
• Terdapat 3 tipe tanaman menurut kemampuan mengurangi terjadinya fotorespirasi, yaitu :
• 1) Tanaman C3
• 2) Tanaman C4
• 3) Tanaman CAM (Crassulacean Acid Metabolism)
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• 1) Tanaman C3
• tanaman pada umumnya, dimana CO2 diubah menjadi senyawa beratom C3 (Gliseraldehid 3-P/GDP), tanaman C3 rentan mengalami fotorespirasi sehingga tidak cocok ditanaman pada musim/daerah kering
• contoh : padi
• 2) Tanaman C4
• tahan kering, tidak mengalami fotorespirasi, CO2 diubah menjadi asam malat (beratom C4), anatomi daun dilengkapi bundle-sheath/seludang berkas pengangkut
• Contoh : jagung, tebu
• 3) CAM
• sangat tahan lingkungan kering, membuka stomata untuk mengambil CO2 pada malam hari, diubah menjadi asam malat, saat siang hari stomata menutup, asam malat kembali diubah jadi CO2
• Contoh : nanas, kaktus, sansiviera
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Figure 10.20
C4 leaf anatomy The C4 pathway
Photosyntheticcells of C4
plant leaf
Mesophyll cell
Bundle-sheathcell
Vein(vascular tissue)
Stoma
Mesophyll cell
PEP carboxylaseCO2
Oxaloacetate (4C) PEP (3C)
Malate (4C)
Pyruvate (3C)
CO2
Bundle-sheathcell
CalvinCycle
Sugar
Vasculartissue
ADP
ATP
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Figure 10.20a
C4 leaf anatomy
Photosyntheticcells of C4
plant leaf
Mesophyll cell
Bundle-sheathcell
Vein(vascular tissue)
Stoma
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Figure 10.20bThe C4 pathway
Mesophyll cell PEP carboxylase
CO2
Oxaloacetate (4C) PEP (3C)
Malate (4C)
Pyruvate (3C)
CO2
Bundle-sheathcell
CalvinCycle
Sugar
Vasculartissue
ADP
ATP
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Sugarcane
Mesophyllcell
Bundle-sheathcell
C4 CO2
Organic acid
CO2
CalvinCycle
Sugar
(a) Spatial separation of steps (b) Temporal separation of steps
CO2
Organic acid
CO2
CalvinCycle
Sugar
Day
Night
CAM
Pineapple
CO2 incorporated
(carbon fixation)
CO2 released
to the Calvin
cycle
2
1
Figure 10.21
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Figure 8.4b
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