photosynthesis powerpoint

PhotosynthesisPhotosynthesis

PhotosynthesisPhotosynthesisPresentation by:Presentation by:

Mr M DlaminiMr M Dlamini201221083201221083

1

PhotosynthesisPhotosynthesisPhotosynthesis, the biochemical process by which plants capture energy from sunlight and

store it in carbohydrates.

Autotrophic organismsAutotrophic organisms use an inorganic use an inorganic form of carbon, e.g. form of carbon, e.g. carbon dioxidecarbon dioxide, to , to make up complex organic compounds, make up complex organic compounds, with energy from two sources: with energy from two sources:

Rhizobium in root nodules

1) light 2) chemicals

4Photosynthetic Organisms


Photosynthesis is more common and Photosynthesis is more common and important because:important because:

1. It provides a source of complex organic molecules for heterotrophic organisms.

2. It releases oxygen for use by aerobic organisms.



Photosynthesis takes place in the green Photosynthesis takes place in the green portions of plantsportions of plantsLeaf of flowering plant contains mesophyll Leaf of flowering plant contains mesophyll tissuetissue

Cells containing chloroplastsCells containing chloroplastsSpecialized to carry on photosynthesisSpecialized to carry on photosynthesis

COCO22 enters leaf through stomata enters leaf through stomataDiffuses into chloroplasts in mesophyll cellsDiffuses into chloroplasts in mesophyll cells In stroma, COIn stroma, CO22 combined with H combined with H22O to form O to form CC66HH1212OO66 (sugar) (sugar)

Energy supplied by lightEnergy supplied by light

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7Leaves and Photosynthesis

PhotosynthesisPhotosynthesisPhotosynthetic Reactions:Photosynthetic Reactions:OverviewOverview

Light ReactionLight Reaction::Chlorophyll absorbs solar energyChlorophyll absorbs solar energyThis energizes electronsThis energizes electronsElectrons move down Electrons move down electron transport chainelectron transport chain Pumps Pumps HH++ into into thylakoidsthylakoids

Used to make Used to make ATPATP out of out of ADPADP and and NADPHNADPH out out of of NADPNADP

Calvin Cycle ReactionCalvin Cycle ReactionCOCO22 is reduced to a carbohydrate is reduced to a carbohydrate Reduction requires the ATP and NADPH Reduction requires the ATP and NADPH produced aboveproduced above

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Light Dependent ReactionsLight Dependent Reactions

A.A. Light absorptionLight absorption1.1. As chlorophyll absorbs light its electrons As chlorophyll absorbs light its electrons

are raised to a higher energy level by are raised to a higher energy level by photons at certain wavelengthsphotons at certain wavelengths

2.2. The electrons at higher energy levels are The electrons at higher energy levels are said to be said to be excited electronsexcited electrons

3.3. The excited electrons cause the The excited electrons cause the chlorophyll to become photoactivatedchlorophyll to become photoactivated

4.4. Photoactivation is the activation of a Photoactivation is the activation of a particular pigment’s electrons (It is particular pigment’s electrons (It is caused by absorbing energy from caused by absorbing energy from photons.)photons.)

10Photosynthesis Overview

PhotosynthesisPhotosynthesisLight Reactions:Light Reactions:The Noncyclic Electron PathwayThe Noncyclic Electron Pathway

Takes place in thylakoid membraneTakes place in thylakoid membraneUses two photosystems, Uses two photosystems, PS-IPS-I andand PS-IIPS-IIPS II captures light energyPS II captures light energyCauses an electron to be ejected from the Causes an electron to be ejected from the reaction reaction

centercenter ( (chlorophyll chlorophyll aa)) Electron travels down electron transport chain to PS IElectron travels down electron transport chain to PS I Replaced with an electron from waterReplaced with an electron from water Which causes HWhich causes H++ to concentrate in thylakoid to concentrate in thylakoid

chamberschambers Which causes Which causes ATP productionATP production

PS I captures light energy and ejects an electronPS I captures light energy and ejects an electron Transferred Transferred permanentlypermanently to a molecule of NADP to a molecule of NADP++

Causes Causes NADPH productionNADPH production

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12Light Reactions:Noncyclic Electron

Pathway

PhotosynthesisPhotosynthesisLight Reactions:Light Reactions:The Cyclic Electron PathwayThe Cyclic Electron Pathway

Uses only photosystem I (PS-I)Uses only photosystem I (PS-I)

Begins when PS I complex absorbs solar Begins when PS I complex absorbs solar energyenergy

Electron ejected from reaction centerElectron ejected from reaction centerTravels down electron transport chainTravels down electron transport chainCauses HCauses H++ to concentrate in thylakoid to concentrate in thylakoid chamberschambers

Which causes Which causes ATP productionATP productionElectron returns to PS-I (cyclic)Electron returns to PS-I (cyclic)

Pathway only results in ATP productionPathway only results in ATP production

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14Light Reactions:Cyclic Electron

Pathway

Chapter715Light-Independent Reactions

NADPH and ATP from light-NADPH and ATP from light-dependent reactions used to power dependent reactions used to power glucose synthesisglucose synthesis

Light not Light not directlydirectly necessary for light- necessary for light-independent reactions if ATP & independent reactions if ATP & NADPH availableNADPH available

Light-independent reactions called Light-independent reactions called the the Calvin-BensonCalvin-Benson CycleCycle or or CC33CycleCycle

Chapter716The C3 Cycle

6 CO6 CO22 used to synthesize 1 glucose used to synthesize 1 glucose (C(C66HH1212OO66))

Carbon dioxide is captured and Carbon dioxide is captured and linked to ribulose bisphosphate linked to ribulose bisphosphate (RuBP)(RuBP)

ATP and NADPH from light ATP and NADPH from light dependent reactions used to power dependent reactions used to power CC33 reactions reactions

PhotosynthesisPhotosynthesisOrganization of theOrganization of theThylakoid MembraneThylakoid Membrane

PS IIPS II:: Pigment complex and electron-acceptorsPigment complex and electron-acceptors Adjacent to an enzyme that oxidizes waterAdjacent to an enzyme that oxidizes water Oxygen is released as a gasOxygen is released as a gas

Electron transport chainElectron transport chain:: Consists of cytochrome complexesConsists of cytochrome complexes Carries electrons between PS II and PS ICarries electrons between PS II and PS I Also pump HAlso pump H++ from the stroma into thylakoid space from the stroma into thylakoid space

PS IPS I:: Pigment complex and electron acceptorsPigment complex and electron acceptors Adjacent to enzyme that reduces NADPAdjacent to enzyme that reduces NADP++ to NADPH to NADPH

ATP synthase complexATP synthase complex:: Has a channel for HHas a channel for H++ flow flow Which drives ATP synthase to join ADP and PWhich drives ATP synthase to join ADP and P ii

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CC33 Cycle Has Three Parts Cycle Has Three Parts

2. 2. Synthesis of Glyceraldehyde 3-Synthesis of Glyceraldehyde 3-Phosphate (G3P)Phosphate (G3P)

Energy is donated by ATP and NADPHEnergy is donated by ATP and NADPH Phosphoglyceric acid (PGA) Phosphoglyceric acid (PGA)

molecules are converted into molecules are converted into glyceraldehyde 3-Phophate (G3P) glyceraldehyde 3-Phophate (G3P) molecules …molecules …

18Chapter 7


CC33 Cycle Has Three Parts Cycle Has Three Parts

3. 3. Regeneration of Ribulose bis-Regeneration of Ribulose bis-phosphate (RuBP)phosphate (RuBP)

10 of 12 G3P molecules converted into 10 of 12 G3P molecules converted into 6 RuBP molecules6 RuBP molecules

2 of 12 G3P molecules used to 2 of 12 G3P molecules used to synthesize 1 glucosesynthesize 1 glucose

ATP energy used for these reactionsATP energy used for these reactions

19Chapter 7


A Summary of PhotosynthesisA Summary of Photosynthesis

20Chapter 7

Light-Light-dependent dependent reactions reactions occur in occur in

thylakoidsthylakoids

Light-Light-independent independent reactions (creactions (c33 cycle) occur cycle) occur

in stromain stroma

21Organization of a Thylakoid

PhotosynthesisPhotosynthesisCalvin Cycle Reactions:Calvin Cycle Reactions:Overview of C3 PhotosynthesisOverview of C3 Photosynthesis

A cyclical series of reactionsA cyclical series of reactions

Utilizes atmospheric carbon dioxide to Utilizes atmospheric carbon dioxide to produce carbohydrates produce carbohydrates

Known as C3 photosynthesisKnown as C3 photosynthesis

Involves three stages: Involves three stages:

Carbon dioxide fixationCarbon dioxide fixation

Carbon dioxide reductionCarbon dioxide reduction

RuBP RegenerationRuBP Regeneration

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PhotosynthesisPhotosynthesisCalvin Cycle Reactions:Calvin Cycle Reactions:Carbon Dioxide FixationCarbon Dioxide Fixation

COCO22 is attached to 5-carbon is attached to 5-carbon RuBP RuBP moleculemolecule

Result in a 6-carbon moleculeResult in a 6-carbon molecule

This splits into two 3-carbon molecules (This splits into two 3-carbon molecules (3PG3PG))

Reaction accelerated by Reaction accelerated by RuBPRuBP Carboxylase Carboxylase (Rubisco)(Rubisco)

COCO22 now “fixed” because it is part of a now “fixed” because it is part of a carbohydratecarbohydrate

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24The Calvin Cycle:

Fixation of CO2

PhotosynthesisPhotosynthesisCalvin Cycle Reactions:Calvin Cycle Reactions:Carbon Dioxide ReductionCarbon Dioxide Reduction

3PG reduced to 3PG reduced to BPGBPG

BPG then reduced to BPG then reduced to G3PG3P

Utilizes NADPH and some ATP produced in Utilizes NADPH and some ATP produced in light reactionslight reactions

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26The Calvin CycleReduction of CO2

InLineFigurep125

PhotosynthesisPhotosynthesisCalvin Cycle Reactions:Calvin Cycle Reactions:Regeneration of RuBPRegeneration of RuBP

RuBP used in CORuBP used in CO22 fixation must be replaced fixation must be replaced

Every three turns of Calvin Cycle,Every three turns of Calvin Cycle,

Five G3P (a 3-carbon molecule) usedFive G3P (a 3-carbon molecule) used

To remake three RuBP (a 5-carbon molecule)To remake three RuBP (a 5-carbon molecule)

5 X 3 = 3 X 55 X 3 = 3 X 5

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28The Calvin CycleRegeneration of

RuBP


Importance of Calvin CycleImportance of Calvin Cycle

G3P (glyceraldehyde-3-phosphate) can be G3P (glyceraldehyde-3-phosphate) can be converted to many other moleculesconverted to many other molecules

The hydrocarbon skeleton of G3P can formThe hydrocarbon skeleton of G3P can form

Fatty acids and glycerol to make plant oilsFatty acids and glycerol to make plant oils

Glucose phosphate (simple sugar)Glucose phosphate (simple sugar)

Fructose (which with glucose = sucrose)Fructose (which with glucose = sucrose)

Starch and celluloseStarch and cellulose

Amino acidsAmino acids

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CC44 Photosynthesis Photosynthesis

In hot, dry climatesIn hot, dry climatesStomata must close to avoid wiltingStomata must close to avoid wiltingCOCO22 decreases and O decreases and O22 increases increasesOO22 starts combining with RuBP instead of CO starts combining with RuBP instead of CO22

PhotorespirationPhotorespiration, a problem solve in C, a problem solve in C44 plants plants

In CIn C44 plants plantsFix COFix CO22 to PEP a C to PEP a C33 molecule moleculeThe result is oxaloacetate, a CThe result is oxaloacetate, a C44 molecule molecule In hot & dry climatesIn hot & dry climates Avoid photorespirationAvoid photorespiration Net productivity about 2-3 times CNet productivity about 2-3 times C33 plants plants

In cool, moist, can’t compete with CIn cool, moist, can’t compete with C33

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31Chloroplast distribution in

C4 vs. C3 Plants

32CO2 Fixation inC4 vs. C3 Plants


CAM PhotosynthesisCAM Photosynthesis

Crassulacean-Acid MetabolismCrassulacean-Acid MetabolismCAM plants partition carbon fixation by timeCAM plants partition carbon fixation by time During the nightDuring the night

CAM plants fix COCAM plants fix CO22

Forms CForms C44 molecules, molecules, Stored in large vacuolesStored in large vacuoles

During daylightDuring daylight NADPH and ATP are availableNADPH and ATP are available Stomata closed for water conservationStomata closed for water conservation CC44 molecules release CO molecules release CO22 to Calvin cycle to Calvin cycle

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34CO2 Fixation in aCAM Plant

Reference list 35

http://www.slideshare.net/201221083/savedfiles?s_title=photosynthesis-29183537&user_login=mazz4

http://www.slideshare.net/201221083/savedfiles?s_title=chapter-7-powerpoint-le&user_login=guest121530

http://www.slideshare.net/201221083/savedfiles?s_title=ap-bio-ch7-power-point&user_login=MrDPMWest







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