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Photosynthesis :, image, image, image - Coggle Diagram
Photosynthesis :
Carbon Metabolism
C4 Photosynthesis
Structural C4 leaf
- Upper epidermis
- Mesophyll cell
- Vein
- Bundle Sheath Cell
- Lower epidermis
- stomata
C4 Pathway
- Atmospheric CO2 is fixed in mesophyll cells to form a simple 4-carbon organic acid (oxaloacetate).
- Fixation by by a non-rubisco enzyme, PEP carboxylase
- Oxaloacetate the converted into malate, so that can be transported into bundle sheath cell
- Inside bundle sheath cell. malate breaks down & releasing CO2
- CO2 then fixed by Rubisco & made into sugar via calvin cycle. Therefore rubisco have to react with CO2 because O2 is absent. (photorespiration not occurs)
- C4 have an adaptation that allow them to be successful in hot dry climate
- eg: maize plant, sugar cane, millet plant & sorghum plant
CAM Photosynthesis
At night
- CAM plants open their stomata,(minimize the loss of water) allowing CO2 diffuse into the leaves
- This CO2 fixed into oxaloacetate by PEP carboxylase then converted into malate
At Day
- Organic acid is stored inside vacuoles until the next day
- CAM plants do not open their stomata in daylight but still can photosynthesize
- Organic acid are transported out of the vacuoles & broken down to release CO2
- CO2 enter the calvin cycle
- Commonly in dessert plants, in warm, arid regions
- CAM plants separate these event by time
- CO2 is fixed during the night
- Calvin cycle reactions occur during the day
C3 Photosynthesis
- The first detected molecules from calvin cycle is 3-carbon compound
- Fixation by RuBP carboxylase (Rubisco) in C3 plant with CO2 & O2
- The photorespiration is RuBP binding O2. This process reduce photosynthesis product yield
If weather hot & dry, C3 plant will
- Closed stomata
- Preventing the loss of H2O
- Prevent CO2 entering leaf
- Traps O2 (by-product of photosynthesis within the leaf space & Spongy mesophyll
- C3 photosynthesis are necessary adaption to minimize photorespiration effect
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Light Reaction
- Light reaction occurs in granum
- Chlorophyll absorbs solar energy to energizes electrons
- ATP is produced using an electron transport chain
- NADP+, coenzyme, accept electrons to form NADPH
- ATP & NADPH produced in thylakoid membrane used in calvin cycle to reduce CO2 to a carbohydrates
Photosystem I & II consist several part:
- Pigment Complex = as an antenna, consist 300 chlorophyll & 40 carotenes & other accessory
- Reaction Center = a special chlorophyll pigment
- Electron Receptor Molecules=
Photosystem II
- photosystem II absorbs solar energy & energizing the electrons in PS II
- Energized electrons are passed to electron acceptors while PS II splits a water molecules to recover the electrons. (release 1/2 O2 + 2H+)
- Electron acceptors sends the energized down an electron transport chain
- Energy is released and stored in the form of H+ gradient in thylakoid
- photosystem II contains a chlorophyll with an absorption peek at 680nm, known as P680
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ATP Synthesis
- during photosynthesis, thylakoid becomes H+ reservoir.
- ion H+ come from two sources, the oxidation of water in PS II & the flow of electrons release energy
- Electron Transport Chain establishes an energy gradient. It carries electron, pass the electron from one to the other.
- As electrons passed down, energy is released & stored in the form of hydrogen ions gradient
- This H+ gradient is used later in photosynthesis to produce ATP
- After ATP synthesized, H+ flow down their concentration gradient & released energy
Calvin Cycle
Regeneration of Ribulose-1,5-bisphosphate
- About 1/6 of G3P is used to make glucose
- The product of calvin cycle is glyceraldehyde-3-phosphate (G3P)
- About 5/6 of glucose is used to regenerate the RuBP
Carbon Dioxide Reduction
- NADPH provides electrons for the
reduction & ATP provides the energy
(6 NADPH :arrow_right: 6 NADP+ & H+)
- NADPH & ATP are used to convert the six-molecules 3-PGA into six-molecules GA3P
- Reduction of Carbon Dioxide is a reaction that uses NADPH & ATP from light reaction to form Carbohydrate
Carbon Dioxide Fixation
- 3 molecules of carbon dioxide from air attached (fixed) to RuBP
- The enzymes for this reaction is RuBP carboxylase oxygenase (rubisco)
- Rubisco splits the resulting 6-carbon molecules to form 3-carbon molecules (PGA)
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Chloroplast
- Has double membrane that surrounds the liquid stroma
- The stroma contains numerous flat thylakoid disc arrange in stacks called grana
- The cholorophyll pigments imbedded in the thylakoid membranes absorb solar energy
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