21168097-Chloroplast-and-Photosynthesis

21168097-Chloroplast-and-Photosynthesis - PH OT OSYN T H E...

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Unformatted text preview: PH OT OSYN T H E PH SI S energy for l i fe The site.. The QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. LEAF MORPHOLOGY LEAF External leaf characteristics (such as shape, External margin, hairs, etc.) are important for identifying plant species plant These structures are a part of what makes leaves These determinant; they grow and achieve a specific pattern and shape, then stop. Other plant parts like stems or roots are nondeterminant, and will usually continue to grow as determinant, long as they have the resources to do so. Classification of leaves can occur through many Classification different designative schema, and the type of leaf is usually characteristic of a species, although some species produce more than one type of leaf. some EPIDERMIS Generally a single layer of cells The "skin" of the plant Primarily parenchyma cells Main role is protection of the plant Often covered with trichomes that may limit the transpiration Also typically covered with stomata for gas exchange Usually transparent and lack chloroplasts Coated on the outer side with a waxy cuticle that prevents water loss Function of epidermis : protection against water loss, regulation of gas exchange, secretion of metabolic compounds, absorption of water Dicot Leaf Cross Section Monocot Leaf Cross Section THE MESOPHYLL THE THE CHLOROPLAST THE THE STRUCTURE.. THE The word chloroplast is derived from the The Greek words chloros which means green and plast which means form or entity. plast Chloroplasts are members of a class of organelles known as plastids. organelles INNER MEMBRANE INNER Inner membrane surrounds the stroma of Inner the plastid the Extension of the inner membrane form Extension the thylakoid membrane. the the photosystem for photosynthesis is the occur at thylakoid membrane occur GRANUM GRANUM Refer to : A thylakoid stack (granum, pl. grana) thylakoid inside chloroplasts. A granum (plural grana) is a stack of granum thylakoid discs. Chloroplasts can have from 10 to 100 grana. Grana are connected by stroma Grana thylakoids, also called intergrana thylakoids or lamellae. Grana thylakoids and stroma thylakoids Grana can be distinguished by their different protein composition. STROMA STROMA The inner matrix of the chloroplast The A colourless matrix in which the colourless lamellae are embedded lamellae A matrix containing dissolved matrix enzymes A fluid surrounds the double fluid membrane of chloroplast membrane FUNCTIONS OF STROMA FUNCTIONS It contain enzyme-rich solution which are It the place where carbon dioxide is first attached to an organic compound and reduced to carbohydrates (calvin cycle) The reactions occur and starches The (sugars) are created in stroma (sugars) THYLAKOID THYLAKOID Any of the flattened saclike structures Any that are stacked on top of another to form the grana. form Chlorophyll and other photosynthetic Chlorophyll pigment are situated in the thylakoid membranes. membranes. LUMEN LUMEN Comes from Latin word lumen opening /light The cavity of a tubular organ in thylakoid Function as Function a)Play a vital role for photophosphorylation a)Play during photosynthesis. during b)Site of water oxidation by the oxygen Site c) The present of electron transport protein c) The plastocyanin in lumen. plastocyanin PHOTOSYNTHESIS CONCEPT CONCEPT Chloroplasts absorb light and use it in Chloroplasts conjunction with water and carbon dioxide to produce sugars, the raw material for energy and biomass production in all green plants and the animals that depend on them, directly or indirectly, for food. indirectly, LIGHT REACTION LIGHT PHOTORECEPTORS PHOTORECEPTORS Chlorophyll Consist of 2 parts : (i) porphyrin; head (ii) long hydrocarbon @ phytol; tail (ii) Made up of 4-nitrogen containing pyrrole ring Made 2+ Mg2+ in the center of the ring Four species of chlorophyll : a, b, c and d Four Structure of Chlorophyll a CHO O Chlorophyll d CH2 CH CH3 CHO Chlorophyll b I N Mg N N N II Chlorophyll a IV CH2 CH2 C=O CH2 CH III pheophytin Chlorophyll c Absorption spectra of chlorophyll a and chlorophyll b chlorophyll Chlorophyll b Absorption Chlorophyll a 400 500 600 Wavelength (nm) 70 0 LIGHT ABSORPTION LIGHT Chlorophyll does not absorb strongly Chlorophyll green of the visible light spectrum (490green 550nm) 550nm) Maximum absorption: blue light (425490nm) and red (640-700nm) PHOTOSYSTEM PHOTOSYSTEM Photosystem (PS) are major components of the photosynthetic Photosystem electron transport chain electron PS; presence of 2 large multi molecular complexes : Photosystem PS; I (PSI) and photosystem II (PSII) (PSI) photosystem These 2 photosystems operate in series linked by a multiprotein These aggregate; called cytochrome complex cytochrome PSI is designated as P700 (pigment with maximum absorbance at PSI P700 700nm) 700nm) PSII designated as P680 (pigment with maximum absorbance at PSII P680 680nm) 680nm) ELECTRON TRANSPORT CHAIN ELECTRON H2 O ½O2 + 2H+ 2e NADPH + H+ PSII Cyt PSI NADP+ + 2H+ ⇨ sequential arrangement of 3 molecules membrance complexes extracts to low-energy electron (from water) and used light energy, produces strong reductant; NADPH + and H+ NADPH Arrangement of PS I, PSII and complex (Cyt b6/ Arrangement complex f) in thylakoid membrane in 4 complexes; CF0 – CF1 coupling factor @ ATP synthase synthase Arrangement - direct movement of protons Arrangement between the stroma and thylakoid between This arrangement give rise to proton gradient This for ATP synthesis for PHOTOLYSIS OF WATER PHOTOLYSIS Water splitting: 2H2O O2 + 4H+ + 4e Occur in PSII Donate electron and proton Product - oxygen PHOTOPHOSPHORYLATION PHOTOPHOSPHORYLATION Photophosphorylation ⇨ light-driven production of ATP by chloroplast by ATP and NADPH are required for reduction of CO2 Formation of ATP through: i. noncyclic @ linear electron transport known as noncyclic photophorylation; and ii. cyclic electron transport known as cyclic photophosphorylation photophosphorylation NONCYCLIC PHOTOPHOSPHORYLATION PHOTOPHOSPHORYLATION Electron continously supplied from water and Electron transfer to NADP+ to from NADPH transfer Establish proton gradient, which in turn drives Establish ATP synthesis ATP Produce ATP and NADPH ­0.6 P700* P680* Feo Redox potential 0 PQ Cyt b6/f fd NADP+ 2 hv>680 nm P700 PC P680 H2O 2 hv≤680 nm +1.0 ½ O2 + 2H+ CYCLIC PHOTOPHOSPHORYLATION CYCLIC Transport electron independently of PSII @ PSI Transport operating independently of PSII operating Return electron from P700* to P700 through Ferridoxin Return P700* through (Fd), ferrodoxin-PQ oxidoreductase (Fdx-PQ), cytochrome b6f complex and Plastoquinone (PC) Oxidation of PQ by cytochrome b6f complex generates Oxidation proton gradient that can be used for ATP synthesis but no NADPH produced no Cyclic electron transport P700* Fd Fdx-PQ PSI PQ FeS Cyt f PC P700 hv>680 nm ATP SYNTHESIS ATP Chemioosmosis In chloroplast, protons are pumped across thylakoid In membrane, from stroma into the lumen Protons carry positive charge ⇨ difference in proton Protons concentration (∆ pH) across the membrane quite large concentration Proton motive force (pmf) = membrane potential difference + proton gradient difference Pump proton into lumen against a proton motive force & Pump large amount of energy is required large Energy required is provided by free energy from Energy intersystem electron transport in photosynthesis intersystem Direction of proton motive force favors the return of Direction proton to the stroma proton Return of proton restricted to proton-lined channel, i.e. Return ATP synthase ATP Model of Chloroplast ATP synthase H+ CF1 stroma pH8 Thylakoid membrane Lumen pH5 CF0 H+ Active site for ATP synthesis ATP Channel to allow Synthase complexs proton return back to stroma SUMMARY SUMMARY Photochemical reactions Occur in thylakoids and grana, produce O2, thylakoids grana produce ATP, and reduced NADP+ (or NADPH). ATP and reduced (or CALVIN CYCLE CALVIN Pathway which all organisms (photosynthetic Pathway eukaryotic) incorporate CO2 into carbohydrate; eukaryotic) known as carbon fixation @ Photosynthetic Carbon Reduction (PCR) cycle @ Calvin cycle Carbon Consume ATP and NADPH produced by Consume ATP NADPH photosynthetic electron transport photosynthetic STAGES STAGES PCR cycle divided into 3 primary stage : (i) Carboxylation ⇨ fixes CO2 in the presence of 5­C acceptor molecule; ribulose bisphosphate (RuBP); and converts into 2 molecules of 3­C acid (ii) Reduction ⇨ consume the ATP and NADPH produced by photosynthetic electron transport to convert the 3­C acid to triose phosphate (iii) Regeneration ⇨ consume additional ATP to convert some of the triose phosphate back into RuBP to ensure the capacity for the continuous fixation of CO2 CO2 PGA ATP ADP 6 1,3­biphosphoglycerate NADPH G3P G3P glucose NADP+ 6Pi RuBP 3 ADP ATP G3P Rubisco Calvin Cycle ...
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This note was uploaded on 12/04/2009 for the course BIOL 230 taught by Professor Gibson during the Spring '09 term at Tennessee Martin.

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