FOTOSINTESIS Diah Rachmawati-2009 Photosynthesis is the process by which green plants, algae, and certain classes of bacteria capture solar energy and use it to make simple sugar molecule

Diah Rachmawati-2009 Fotosintesis

Tempat fotosintesis berlangsung ? Diah Rachmawati-2009 Tempat fotosintesis berlangsung ? Fotosintesis terjadi di kloroplas Dalam kloroplas terdapat pigmen disebut klorofil. Klorofil berperan penting dalam mengubah energi cahaya menjadi energi kimia Vein Leaf cross section Mesophyll CO2 O2 Stomata The process of photosynthesis occurs within the chloroplasts of plant cells. These cell organelles contain numerous chlorophyll pigments, which absorb mostly blue and red wavelengths of sunlight. Most photosynthesis occurs in the plant leaves because the cells within these plant organs have the highest concentration of chloroplasts. In the presence of light energy, six carbon dioxide molecules combine with six water molecules. This reaction produces one simple sugar molecule, along with six molecules of oxygen. A plant uses the oxygen molecules produced during photosynthesis for other chemical processes occurring at the same time as photosynthesis. Excess oxygen molecules pass through the open stomata of the plant leaves and escape into the air. Water within the plant transports the sugar molecules from the leaves to other parts of the plant, where they are converted into molecules of carbohydrates, lipids, proteins, cellulose, and lignin. Di bagian daun terdapat bagian yang disebut mesofil. Dalam mesofil terdapat jaringan palisade yang kaya akan kloroplas. Jaringan berklorofil misal daun pada tanaman merupakan tempat utama terjadinya fotosintesis. a

Diah Rachmawati-2009 moodle.learningnetworks.com

Daun – struktur kloroplas Diah Rachmawati-2009 Daun – struktur kloroplas

Diah Rachmawati-2009 Struktur kloroplas Chloroplast Mesophyll 5 µm Outer membrane Intermembrane space Inner Thylakoid Granum Stroma 1 µm Tilakoid adalah sistem membran dalam kloroplas (tempat terjadinya reaksi terang). Memisahkan kloroplas menjadi ruang tilakoid dan stroma Grana kumpulan tilakoid dalam kloroplas Stroma: daerah cair antara tilakoid dan membran dalam tempat terjadi siklus Calvin

Persamaan Fotosintesis Diah Rachmawati-2009 Persamaan Fotosintesis

Fotosintesis Fotosintesis terdiri dari dua proses yaitu -Reaksi terang Diah Rachmawati-2009 Fotosintesis Fotosintesis terdiri dari dua proses yaitu -Reaksi terang -Reaksi reduksi karbon (Siklus Calvin) Reduksi CO2 menjadi karbohidrat melalui oksidasi carrier energi (ATP, NADPH) Reaksi terang memberi energi pada carrier Reaksi reduksi karbon (siklus Calvin) menghasilkan PGAL (phosphoglyceraldehyde)

Diah Rachmawati-2009 Light Chloroplast NADP ADP + P RuBP 3-PGA reactions Calvin cycle Electrons G3P Cellular respiration Cellulosse Starch Other organic compounds Fotosintesis Proses dimana organisme yang memiliki kloroplas mengubah energi cahaya menjadi energi kimia Melibatkan 2 lintasan metabolik Reaksi terang: mengubah energi cahaya menjadi energi selular Siklus Calvin: reduksi CO2 menjadi CH2O

Diah Rachmawati-2009 Reaksi Terang Energi cahaya akan diubah menjadi energi kimia dengan menghasilkan oksigen sebagai produk samping. Terjadi di dalam membran tilakoid. Energi cahaya yang diserap klorofil dalam membran tilakoid akan digunakan untuk membentuk ATP dari ADP dan fosfat. Pada fase ini terjadi fotolisis air yang menghasilkan oksigen.

Diah Rachmawati-2009 Cahaya Photosynthetically active radiation (PAR).

The role of light Light provides the energy to: Diah Rachmawati-2009 The role of light Light provides the energy to: transfer electrons from water to nicotinamide adenine dinucleotide phosphate NADP+) forming NADPH; Generate ATP the removal of hydrogen (H) atoms from water molecules the reduction of carbon dioxide (CO2) by these hydrogen atoms to form organic molecules.

-Substansi yang menyerap cahaya tampak Diah Rachmawati-2009 Pigmen -Substansi yang menyerap cahaya tampak -Menyerap kebanyakan panjang gelombang tetapi paling sedikit menyerap panjang gelombang hijau Pigmen Klorofil a Klorofil b Karotenoid Karotene Xantofil In addition to their role as accessory pigments, carotenoids play an essential role in photoprotection

Diah Rachmawati-2009 Klorofil a Klorofil a adalah pigmen yang secara langsung berpartisipasi dalam reaksi terang Pigmen lain menambahkan energi ke klorofil a Penyerapan cahaya meningkatkan elektron ke orbital energi yang lebih tinggi

Diah Rachmawati-2009 Fotosistem Fotosistem merupakan unit pengumpul cahaya dari membran tilakoid. Setiap fotosistem berupa kompleks dari protein dan jenis protein dan jenis molekul lainnya, termasuk antena yang terdiri dari beberapa ratus molekul pigmen. Pada pusat reaksi energi ini menggerakkan reaksi reduksi-oksidasi. Elektron tereksitasi dari klorofil pusat reaksi dan ditangkap oleh molekul khusus yang disebut akseptor elektron primer.

Diah Rachmawati-2009 Fotosistem Kumpulan pigmen dan protein yang berasosiasi dengan membran tilakoid yang memanen energi dari elektron yang tereksitasi Energi yang ditangkap ditransfer antara molekul fotosistem sampai mencapai molekul klorofil pada pusat reaksi

Pada pusat reaksi terdapat 2 molekul Klorofil a Diah Rachmawati-2009 Pada pusat reaksi terdapat 2 molekul Klorofil a Akseptor elektron primer Pusat reaksi klorofil dioksidasi dengan hilangnya elektron melalui reduksi akseptor elektron primer Membran tilakoid Terdapat fotosistem I dan II

Klorofil tereksitasi oleh cahaya Saat pigmen menyerap cahaya Diah Rachmawati-2009 Klorofil tereksitasi oleh cahaya Saat pigmen menyerap cahaya Klorofil tereksitasi dan menjadi tidak stabil Excited state Energy of election Heat Photon (fluorescence) Chlorophyll molecule Ground e– Primary acceptor

Fotofosforilasi Nonsiklik Diah Rachmawati-2009 Fotofosforilasi Nonsiklik Reaksi fotofosforilasi nonsiklik adalah reaksi dua tahap yang melibatkan dua yaitu fotosistem I dan II. Menghasilkan NADPH, ATP, dan oksigen

Non-cyclic photophosphorilation Light energy is absorbed by antenna pigments of PS II. Energy then transferred to the reaction centre of pigment P680 in PS II. The P680 becomes photoactivated and high energy (“exited”) electron is released to the primary electron acceptor 3. The electron released is replaced by splitting water into its component. This process is called photolysis

4. The electron is then transferred through plastoquinone, cytochrome complex, plastocyanin & PS I. As electron passed along ETC, they lose energy. The energy released is used to produced ATP 5. High energy electron in P700 (PS I) is ejected, passes onto electron acceptor then to ferredoxin & NADP+ reductase 6. NADP+ reductase donates the electron to a molecule of NADP+ and stabilizes it by adding a proton to form NADPH. NADPH is then released into the stroma.

Non cyclic photophosporylation Light energy is absorbed by antenna pigments of PS II. Energy then transferred to the reaction centre of pigment P680 in PS II.

The P680 becomes photoactivated and high energy (“exited”) electron is released to the primary electron acceptor The electron released is replaced by splitting water into its component. This process is called photolysis

Water photolysis Photolysis is a process of splitting water molecules using light energy with the release of electrons and photons and oxygen. The photon (H+) are used to reduced NADP+. Oxygen is given off or used in respiration. 2H2O 4H+ + O2 + 4e- The important of photolysis = To replace electron in photosystem II (non-cyclic photophosphorylation) H+ ions reduce NADP+ to NADPH, which is an electron carrier

The electron is then transferred through plastoquinone, cytochrome complex, plastocyanin & PS I. As electron passed along ETC, they lose energy. The energy released is used to produced ATP

High energy electron in P700 (PS I) is ejected, passes onto electron acceptor then to ferredoxin & NADP+ reductase

NADP+ reductase donates the electron to a molecule of NADP+ and stabilizes it by adding a proton to form NADPH. NADPH is then released into the stroma.

Aliran elektron siklik Hanya fotosistem I yang digunakan Pergerakan elektron dimulai dari fotosistem I dan berakhir di fotosistem I. Hanya ATP yang dihasilkan Diah Rachmawati-2009 Diah Rachmawati-2011

Diah Rachmawati-2009 Aliran elektron Terdapat dua rute jalur elektron yang tersimpan pada akseptor elektron primer Dimulai dengan penangkapan energi foton Menggunakan rantai transport elektron dengan sitokrom untuk kemiosmosis Aliran elektron nonsiklik Menggunakan fotosistem II dan I Elektron dari fotosistem II dihilangkan dan diganti oleh elektron yang didonasikan oleh air Mensintesis ATP dan NADPH Donasi elektron mengkonversi air → O2 dan 2H+ Aliran elektron siklik Hanya menggunakan fotosistem I Elektron dari fotosistem I di-recycle Mensintesis ATP

Non cyclic photophosporylation Cyclic photophosporylation Photosystem I & photosystem II are involved. Only Photosystem I is involved Electron flow is non-cyclic Electron flow is cyclic Water is the first electron donor Electron come from photosystem I (P700) Last electron acceptor is NADP+ Last electron acceptor is photosystem I Products are ATP, NADPH and O2 ATP is produced Reaksi terang menghasilkan NADPH, ATP, and O2

Reaksi terang dan kemiosmosis: Diah Rachmawati-2009 Reaksi terang dan kemiosmosis: LIGHT REACTOR NADP+ ADP ATP NADPH CALVIN CYCLE [CH2O] (sugar) STROMA (Low H+ concentration) Photosystem II H2O CO2 Cytochrome complex O2 1 1⁄2 2 Photosystem I Light THYLAKOID SPACE (High H+ concentration) Thylakoid membrane synthase Pq Pc Fd reductase + H+ NADP+ + 2H+ To Calvin cycle P 3 H+ 2 H+ +2 H+ kemiosmosis adalah difusi ion yang melewati suatu membran. Proses ini berhubungan dengan pembentukan ATP karena pergerakan ion hidrogen yang melewati membran. Ion hidrogen atau proton akan mengalami difusi dari tempat yang konsentrasi ion nya tinggi ke tempat yang konsentrasi ion nya rendah. Kemiosmosis adalah difusi ion yang melewati suatu membran. Proses ini berhubungan dengan pembentukan ATP karena pergerakan ion hidrogen yang melewati membran.

Diah Rachmawati-2009 chemiosmosis Inside the thylakoid lumen, hydrogen ions (H+) accumulate from water splitting and from a coupling of the electron flow with an inward transfer of H+ from the stroma. The H+ being positively charged, this also makes the lumen more electropositive and the stroma more electronegative. The combined concentration gradient and electric potential gradient make a free energy gradient for the H+, favouring their outward movement from the lumen into the stroma. The thylakoid membrane is highly impermeable to H+. But it contains ATP-synthase enzyme complexes, with a proton channel through which the H+ move to the stroma, and this movement, down their free energy gradient, is coupled with ATP synthesis.

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Reaksi Gelap atau Siklus Calvin Diah Rachmawati-2009 Reaksi Gelap atau Siklus Calvin Senyawa gula dibentuk dari CO2 (karbondioksida). Fase ini tidak terlibat langsung dalam pemanfaatan cahaya. Terjadi dalam stroma dari kloroplas.

Diah Rachmawati-2009 Carbon Fixation All plants carry on photosynthesis by adding carbon dioxide (CO2) to a phosphorylated 5-carbon sugar called ribulose bisphosphate. This reaction is catalyzed by the enzyme ribulose bisphosphate carboxylase oxygenase (RUBISCO). The resulting 6-carbon compound breaks down into two molecules of 3-phosphoglyceric acid (PGA). These 3-carbon molecules serve as the starting material for the synthesis of glucose and other food molecules. The process is called the Calvin cycle and the pathway is called the C3 pathway.

Siklus calvin terjadi di stroma Diah Rachmawati-2009 Siklus Calvin menggunakan ATP dan NADPH untuk mengkonversi CO2 menjadi gula Siklus calvin terjadi di stroma Siklus Calvin memiliki 3 tahap Fiksasi karbon Reduksi Regenerasi akseptor CO2 (RuBP)

Dikatalisasi oleh enzim RuBP carboxylase oxygenase (Rubisco). Diah Rachmawati-2009 Sebuah molekul CO2 dikonversi dari bentuk inorganiknya menjadi molekul organik (fixation) melalui pengikatan ke gula 5C (ribulose bisphosphate atau RuBP). Dikatalisasi oleh enzim RuBP carboxylase oxygenase (Rubisco). Bentuk gula 6C pecah menjadi 3-phosphoglycerate Tiap molekul 3-phosphoglycerate menerima tambahan grup fosfat membentuk 1,3-Bisphosphoglycerate (fosforilasi ATP) NADPH dioksidasi dan elektron yang ditransfer ke 1,3-Bisphosphoglycerate memecah molekul dengan tereduksi menjadi Glyceraldehyde 3-phosphate Tahap terakhir dari siklus ini adalah regenerasi RuBP Glyceraldehyde 3-phosphate dikonversi menjadi RuBP melalui sebuah seri reaksi yang melibatkan fosforilasi molekul oleh ATP

Siklus Calvin Diah Rachmawati-2009 Input Light 3 CO2 CALVIN CYCLE (G3P) Input (Entering one at a time) CO2 3 Rubisco Short-lived intermediate 3 P P Ribulose bisphosphate (RuBP) 3-Phosphoglycerate 6 P 6 1,3-Bisphoglycerate 6 NADPH 6 NADPH+ Glyceraldehyde-3-phosphate 6 ATP 3 ATP 3 ADP CALVIN CYCLE 5 1 G3P (a sugar) Output Light H2O LIGHT REACTION ATP NADPH NADP+ ADP [CH2O] (sugar) CALVIN CYCLE O2 6 ADP Glucose and other organic compounds Phase 1: Carbon fixation Phase 3: Regeneration of the CO2 acceptor (RuBP) The Calvin cycle consumes two molecules of NADPH and three molecules of ATP for every CO2 fixed 6 CO2 + 11 H2O + 12 NADPH + 18 ATP → Fructose-6-phosphate + 12 NADP+ + 6 H+ + 18 ADP + 17 Pi Phase 2: Reduction

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Siklus Calvin Dimulai dari CO2 dan menghasilkan 3-phosphoglycerate Diah Rachmawati-2009 Siklus Calvin Dimulai dari CO2 dan menghasilkan 3-phosphoglycerate Tiga bagian siklus Calvin menghasilkan 1 produk molekul Tiga tahap Fiksasi karbon Reduksi CO2 Regenerasi RuBP The Calvin cycle consumes two molecules of NADPH and three molecules of ATP for every CO2 fixed 6 CO2 + 11 H2O + 12 NADPH + 18 ATP → Fructose-6-phosphate + 12 NADP+ + 6 H+ + 18 ADP + 17 Pi

The Calvin cycle proceeds in three stages: Diah Rachmawati-2009 The Calvin cycle proceeds in three stages: Carboxylation of the CO2 acceptor ribulose-1,5-bisphosphate, forming two molecules of 3-phosphoglycerate, the first stable intermediate of the Calvin cycle Reduction of 3-phosphoglycerate, forming gyceraldehyde- 3-phosphate, a carbohydrate Regeneration of the CO2 acceptor ribulose-1,5-bisphosphate from glyceraldehyde-3-phosphate

C4 Plants Help fight transpiration by keeping their stomata partially closed during the day and partially closed at night. Fix carbon dioxide into a temporary storage molecule that has four carbons It is called a C4 pathway because the first stable compound that carbon dioxide is fixed into is a four carbon compound. The four carbon compound is transported to specialized cells where Calvin Cycle is taking place The four carbon compound releases carbon dioxide to run Calvin Cycle.

Tumbuhan C4 Senyawa yang terbentuk pertama kali setelah berikatan dengan CO2 adalah senyawa berkarbon empat (oksaloasetat). Tempat terjadinya fotosintesis terjadi di dua tempat yaitu sel mesofil (siklus C3) dan sel seludang pembuluh (siklus C4). Tumbuhannya seperti sorgum, amaranthus, jagung. Tumbuhan C4 → kemampuan melaksanakan fotosintesis lebih tinggi dan lebih tahan terhadap kekeringan.

Tumbuhan C4 Tumbuhan C4 meminimalkan keperluan fotorespirasi Diah Rachmawati-2009 Tumbuhan C4 Tumbuhan C4 meminimalkan keperluan fotorespirasi dengan cara menggabungkan CO2 ke dalam senyawa empat karbon di sel mesofil Senyawa empat karbon tersebut Dieksport ke sel seludang berkas pengangkut (cell bundle sheath), dimana CO2 dilepaskan yang digunakan dalam siklus Calvin

C4 Plants Corn, sugar cane and crab grass

C4 Photosynthesis: The first fixation is a 4-carbon compound

The basic C4 cycle consists of four stages: Diah Rachmawati-2009 The basic C4 cycle consists of four stages: Fixation of CO2 by the carboxylation of phosphoenolpyruvate in the mesophyll cells to form a C4 acid (malate and/or aspartate) Transport of the C4 acids to the bundle sheath cells Decarboxylation of the C4 acids within the bundle sheath cells and generation of CO2, which is then reduced to carbohydrate via the Calvin cycle Transport of the C3 acid (pyruvate or alanine) that is formed by the decarboxylation step back to the mesophyll cell and regeneration of the CO2 acceptor phosphoenolpyruvate

The C4 photosynthetic pathway Diah Rachmawati-2009 The C4 photosynthetic pathway

CAM Plants Keep stomata CLOSED during the day and OPEN at night. Store carbon dioxide as an organic acid. The organic acid then releases carbon dioxide directly to the Calvin Cycle. CAM plants grow very slowly, but they require less water than C3 or C4 plants.

Desert plants indeed are slow growing, but they are very competitive in hot, dry environments.

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Crassulacean acid metabolism (CAM) Diah Rachmawati-2009 Crassulacean acid metabolism (CAM) Temporal separation of CO2 uptake from photosynthetic reactions: CO2 uptake and fixation take place at night, and decarboxylation and refixation of the internally released CO2 occur during the day. The adaptive advantage of CAM is the reduction of water loss by transpiration, achieved by the stomatal opening during the night. In both C4 and CAM plants, PEP carboxylase is inhibited by malate and activated by glucose-6-phosphate

Comparison C3 Plants C4 Plants CAM Plants Stomata Open during Day and Closed at Night Partially closed during day and partially closed at night Closed during day and Open at night Carbon fixation Carbon dioxide is “fixed” into a three carbon compound that is stable Carbon dioxide is spatially stored as a 4 carbon stable compound Carbon dioxide is temporarily stored as an organic acid. Water Loss Has trouble with water loss due to transpiration. Trouble with photorespiration Less water loss than C3 plants. Photorespiration is not a problem Grow very slowly and no problems with photorespiration What are the advantages of C4 and CAM over C3 photosynthesis, in relation to the leaf and stomata?   Describe three specific differences in the processes of C4 and CAM compared to the prosseses that occur in C3 photosynthesis

SYNTHESIS OF STARCH AND SUCROSE Diah Rachmawati-2009 SYNTHESIS OF STARCH AND SUCROSE

SYNTHESIS OF STARCH AND SUCROSE Diah Rachmawati-2009 SYNTHESIS OF STARCH AND SUCROSE Both starch and sucrose are synthesized from the triose phosphate that is generated by the Calvin cycle Starch is synthesized in the chloroplast and starch in the cytosol The relative concentrations of orthophosphate and triose phosphate are major factors that control whether photosynthetically fixed carbon is partitioned as starch in the chloroplast or as sucrose in the cytosol.

Diah Rachmawati-2009 FOTORESPIRASI

Diah Rachmawati-2009 RUBISCO Rubisco (D-ribulose-1,5-bisphosphate carboxylase/oxygenase) catalyzes the addition of carbon dioxide to D-ribulose-1,5-bisphosphate to form two molecules of 3-phospho-D-glycerate, the initial step in the C3 photosynthetic carbon reduction cycle, and is the world’s most abundant enzyme. Rubisco has very strict specificity for the carbohydrate substrate, but it also catalyzes an oxygenase reaction in which O2 replaces CO2

Diah Rachmawati-2009 Rubisco has ability to catalyze both the carboxylation and the oxygenation of RuBP. Photoinhibition is a complex set of molecular processes, defined as the inhibition of photosynthesis by excess light.

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Diah Rachmawati-2009 Photorespiration Higher plants, which fix carbon via the C3 pathway, exhibit the process of photorespiration Rubisco catalyzes the fixation of both C02 and O2 Photorespiratory pathway involves the activities of at least three different three different cellular organelles (chloroplast, peroxisome, and mitochondrion Fotorespirasi terjadi dalam kondisi [CO2] rendah dan suhu tinggi (Photorespiratory Carbon Oxidation (PCO) Cycle) oksidasi karbon fotorespirasi PCO Kemungkinan juga berfungsi untuk melepaskan kelebihan ATP dan NADPH sehingga terhindar dari fotooksidasi dan fotoinhibisi Fakta terbaru (rekayasa genetika) menunjukkan bahwa fotorespirasi melindungi tanaman C dari fotooksidasi dan fotoinhibisi

C3 Photosynthesis : C3 plants Diah Rachmawati-2009 C3 Photosynthesis : C3 plants Called C3 because the CO2 is first incorporated into a 3-carbon compound. Stomata are open during the day. RUBISCO, the enzyme involved in photosynthesis, is also the enzyme involved in the uptake of CO2. Photosynthesis takes place throughout the leaf. Adaptive Value: more efficient than C4 and CAM plants under cool and moist conditions and under normal light because requires less machinery (fewer enzymes and no specialized anatomy). Most plants are C3.

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Diah Rachmawati-2009 Sel sel Mesofil bunga karang dan sel-sel parenkim seludang berkas pengangkut (Bundle sheath cells) Two steps of C4 photosynthesis that occur in the mesophyll cells are the light-dependent reactions and a preliminary fixation of CO2 into a molecule called malate. CO2 is released from malate in the bundle sheath cells, where it is fixed again by Rubisco and the Calvin-Benson cycle. The PEP is then recycled back to the mesophyll cells, and the carbohydrate products of photosynthesis are distributed through the plant.

Anatomi daun C4 dan jalur C4 Diah Rachmawati-2009 Anatomi daun C4 dan jalur C4 CO2 Mesophyll cell Bundle- sheath cell Vein (vascular tissue) Photosynthetic cells of C4 plant leaf Stoma Mesophyll C4 leaf anatomy PEP carboxylase Oxaloacetate (4 C) PEP (3 C) Malate (4 C) ADP ATP Sheath Pyruate (3 C) CALVIN CYCLE Sugar Vascular tissue Pada tumbuhan C4, sel seludang pembuluh – siklus Calvin proses fotosintesis

Diah Rachmawati-2009 C4 plant : sugar beet, corn CAM plant : pinneapples Cell bundle sheath: Sel selubung berkas pengangkut

Tanaman CAM (Crassulacean Acid Metabolism) Diah Rachmawati-2009 Tanaman CAM (Crassulacean Acid Metabolism) Membuka stomatanya pada malam hari, menggabungkan CO2 ke dalam asam organik Selama siang hari, stomata tertutup CO2 dilepaskan dari asam organik untuk digunakan dalam siklus Calvin Contoh tanaman C4: kaktus, pineapple (bromeliads)

The CO2 joins with PEP to form the 4-carbon oxaloacetic acid. Diah Rachmawati-2009 At night, CAM plants take in CO2 through their open stomata (they tend to have reduced numbers of them). The CO2 joins with PEP to form the 4-carbon oxaloacetic acid. This is converted to 4-carbon malic acid that accumulates during the night in the central vacuole of the cells. In the morning, the stomata close (thus conserving moisture as well as reducing the inward diffusion of oxygen). The accumulated malic acid leaves the vacuole and is broken down to release CO2. The CO2 is taken up into the Calvin (C3) cycle. These adaptations also enable their owners to thrive in conditions of high daytime temperatures intense sunlight low soil moisture.

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Jalur CAM mirip dengan jalur C4 Diah Rachmawati-2009 Jalur CAM mirip dengan jalur C4 Spatial separation of steps. In C4 plants, carbon fixation and the Calvin cycle occur in different types of cells. (a) Temporal separation of steps. In CAM plants, carbon fixation and the Calvin cycle occur in the same cells at different times. (b) Pineapple Sugarcane Bundle- sheath cell Mesophyll Cell Organic acid CALVIN CYCLE Sugar CO2 C4 CAM CO2 incorporated into four-carbon organic acids (carbon fixation) Night Day 1 2 Organic acids release CO2 to Calvin cycle

Sumber Pustaka Neil A. Campbell, Jane B. Reece. 8th. 2008. Biology. Pearson Education, Inc. Öpik, H. & S. Rolfe 2005. The Physiology of Flowering Plants Fourth Edition. Cambridge University Press, Cambridge. UK Taiz, L. & E. Zeiger. 2002. Plant Physiology Third Edition. Sinauer Associates, Inc. Massachusetts.

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