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Photosynthesis Light energy chemical energyLight energy (kinetic) converted into chemical energy (potential) Anabolic, endergonic 6CO 2 + 6H 2 O C 6 H.

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Presentation on theme: "Photosynthesis Light energy chemical energyLight energy (kinetic) converted into chemical energy (potential) Anabolic, endergonic 6CO 2 + 6H 2 O C 6 H."— Presentation transcript:

1 Photosynthesis Light energy chemical energyLight energy (kinetic) converted into chemical energy (potential) Anabolic, endergonic 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2

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4 Leaves ChlorophyllChlorophyll = 1 o pigment – in chloroplasts Mesophyll – ‘middle leaf’, 2 layers of cells in the middle of the leaf –Most of the chloroplasts Stomata = pores in leaf –Gas exchange Vascular bundles - veins –Transport water in and glucose out

5 Photosynthesis 2 step process:2 step process: –‘Light reactions’ Water is splitWater is split ATP generatedATP generated H + gatheredH + gathered –Calvin Cycle - CO 2 incorporated into other organic molecules

6 Chloroplasts Site of photosynthesis Divided into three areas –Intermembrane space –Thylakoid – folded membrane –Stroma – ‘soup’ of water + enzymes + organic molecules

7 Light reactions in thylakoid membrane, and thylakoid space. Calvin cycle in stroma

8 Photosynthetic Pigments Chlorophyll ‘green leaf’ –A-G –Primary pigment –Protein Accessory pigments –Absorb other wavelengths of light –Carotenoids – yellow, orange, red

9 Chlorophyll absorbs best at what colors? What color does chlorophyll not absorb

10 Check Point Organisms that make their own sugars from the raw materials ____ and ___ are called _____ _____ cannot make their own food Most chloroplasts are in the ___ of the leaf ___ is the primary pigment of photosynthesis How is the structure of the chloroplast similar to mitochondria? The ‘middle’ of the mitochondria is the ___; the middle of the chloroplast is the ___ Chlorophyll absorbs mostly ___ and ___ light

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14 Light Reactions Production of ATPProduction of ATP Capture of H + by NADPCapture of H + by NADP Splitting of waterSplitting of water Formation of O 2Formation of O 2

15 Photoexcitation of Chlorophyll e_e_ e_e_ Heat Fluorescence : Photon Chlorophyll

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17 Photosystems Clusters of Pigment Molecules That Absorb Light

18 Photoexcitation of Chlorophyll PhotosystemPhotosystem = cluster of pigment molecules –Chlorophyll a, b, and accessory pigments Most molecules are ‘antennae’ –Pass excited energy to one chlorophyll a Reaction centerReaction center - chlorophyll molecule

19 photosystem Electron not allowed to drop back to ground state

20 2 Types of Photosystems Named in order of discovery Photosystem IPhotosystem I Photosystem IIPhotosystem II Photosystem IIPhotosystem II is ‘beginning’

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25 PS II receives light photons Electrons (e - ) from chlorophyll become ‘excited’ Excited electrons picked up by 1 o acceptor molecule

26 Enzyme splits water releasing e - and oxygen; e - goes to P680 replacing the lost one

27 e - passed down an ETC; produces ATP

28 Photosystem II Excited electrons passed down ETC to PS I (series of cytochromes)Excited electrons passed down ETC to PS I (series of cytochromes) PhotophosphorylationPhotophosphorylation Electrons from water are extracted and donated back to PS II (cycle) Water splits into H 2 + O 2 (waste)

29 e - travels ETC to Photosystem I; P700 boosts e - to its primary acceptor

30 e - passed from I down ETC to NADP; NADPH goes to Calvin

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32 Photosystems are embedded into the membrane

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37 Cyclic photophosphorylation

38 Check Point Light-dependent reactions convert _ to _ energy ____ occurs when energized electrons fall back to their ground state and emit light Pigments that also absorb light in photosynthesis are called ___ ____ is the process whereby energized electrons provide energy to add a phosphate to ADP to make ATP

39 Electrons are passed through the __ during the ETC The buildup of protons in the thylakoid space creates a ____ Protons ‘leak’ out of the thylakoid space through ____ generating ___ ___ and __ are produced by __ ____ ________ Only ATP is generated by ___ ___________

40 Melvin Calvin Used radioactive isotope tracers and determined the sequence of events in carbon fixationUsed radioactive isotope tracers and determined the sequence of events in carbon fixation –Lab next to atomic reactor Also used H 2 to discover that water is the source of HAlso used H 2 to discover that water is the source of H

41 Calvin Cycle Similar to Kreb’sSimilar to Kreb’s Ribulose Biphosphate (RuBP) is ‘fixed’ w/ CO 2 (from ______?)Ribulose Biphosphate (RuBP) is ‘fixed’ w/ CO 2 (from ______?) Uses Ribulose Bisphosphate carboxylase…Uses Ribulose Bisphosphate carboxylase… Rubisco (#1 enzyme)Rubisco (#1 enzyme) Three ‘phases’ –Carbon fixation - –Carbon fixation - C added to RuBP –Reductionaddition of H from NADPH –Reduction: addition of H from NADPH –Regeneration of RuBP: –Regeneration of RuBP: CO 2 acceptor

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45 Calvin Cycle RuBP (5C) + 3 CO 2 (1C) = 18C PGA (3C) = 18 C + 6 H are added from Light Reactions PGAL – 1G3P = 5 PGAL (3C); 53 5 PGAL (15C) = 3 RuBP (15C) Requires 2 cycles of Calvin to make 1 glucose (6C)

46 Check Point The process of carbon fixation is called _____ The two products of the light reaction ___ and __ are used to fix carbon to carbon compounds to make ___ The Calvin Cycle starts when one CO 2 is added to ___ by the enzyme ___ Ribulose bisphosphate to converted to ___ ___ and ___ added to PGA to make ___ One molecule of ___ is made for every 3 CO 2 ’s fixed during the Calvin Cycle


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