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13 Cards in this Set
- Front
- Back
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Structure of Chloroplasts
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- Have double membrane = chloroplast envelope
- Thylakoids stack to create grana. Grana are linked by thylakoid membrane (Lamellae) - Chloroplasts contain pigments. These absorb light energy. Found in thylakoid membranes, attached to proteins = photosystem. - photosystem = primary and accessory pigments. - Two photosystems - photosystem I and photosystem II -Stroma surrounds thylakoids within inner membrane |
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Name three pigments that are present in chlorplasts.
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Chlorphyll a, chlorphyll b and Carotene
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What are Primary pigments?
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Primary pigments are reaction centres where electrons are excited during the light-dependent reaction
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What are accessory pigments?
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Accessory pigments surround the primary pigments and transfer light energy to them
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Photosystem I
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Absorbs light best at a wavelength of 700nm
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Photosystem II
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Absorbs light best at 680nm
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The Light-dependent reaction
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- Requires light energy
- Occurs in Thylakoid membrane - Light energy is absorbed by photosynthetic pigments in the photosystems and converted to chemical energy. -Light energy used to add phosphate to ADP to form ATP and also to form reduced NADP. - H20 is Oxidised to O2. -ATP tranfers energy and reduced NADP tranfers hydrogen to the light-independent reaction. |
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The Light-independent reaction
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- Also known as Calvin Cycle and does not use light energy directly
- Takes place in stroma of chloroplasts - Here, ATP and reduced NADP from light-dependent reaction supply ebergy and hydrogen to mak glucose from CO2 |
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The Calvin Cycle (more detail)
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-CO2 is fixed by combination with RuBP
-Enzyme ribulose bisphosphate carboxylase catalyses this -GP produced is changed to Triose Phosphate using energy from ATP -Hydrogen from NADPH reduces GP to triose phosphate -Some of the TP used to produce hexose sugars, most used to regenerate RuBP (needs ATP) |
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What are the products of the Calvin Cycle?
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Hexose sugars
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Cyclic photophosphorylation
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-Occurs in photosystem I in the grana of chloroplasts
- Excited electrons are used to generate ATP via electron carriers. -electron returns to same photosystem it left Products = ATP |
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Non-cyclic photophosphorylation
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-Occurs in photosystem I and II in grana
- Water is split by photolysis -Excited electrons used to generate ATP -NADP reduced by H+ ions from photolysis -electrons return to different photosystem Products=ATP, Reduced NADP and oxygen as a waste product |
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Chemiosmosis
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-Occurs across thylakoid membranes
-H+ ions pumped into thylakoid space when electron is passed along carriers -Then flow down concentration gradient throught ATP synthase -Generates ATP (product) |
