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Chapter 9Chapter 9
PhotosynthesisPhotosynthesis
This is CHAPTER 9 in your text…….ignore This is CHAPTER 9 in your text…….ignore the “chapter 7” title at the top of each the “chapter 7” title at the top of each powerpoint page. powerpoint page.
Chapter 7 2
Chapter 7 3
What Is Photosynthesis?What Is Photosynthesis?
PhotosynthesisPhotosynthesis is the ability to capture is the ability to capture sunlight energy and convert it to chemical sunlight energy and convert it to chemical energyenergy
Most forms of life on Earth depend on the Most forms of life on Earth depend on the chemical energy produced by chemical energy produced by photosynthetic organismsphotosynthetic organisms
Chapter 7 4
The Photosynthetic EquationThe Photosynthetic Equation
6CO2 carbondioxide
+ 6H2O water
+ light energy sunlight
C6H12O6
glucose (sugar)
+ 6O2
oxygen
Photosynthesis occurs in plants, algae, and Photosynthesis occurs in plants, algae, and some prokaryotessome prokaryotesPhotosynthetic organisms are Photosynthetic organisms are autotrophsautotrophs (“self- (“self-
feeders”)feeders”)Photosynthesis in plants occurs within Photosynthesis in plants occurs within chloroplastschloroplasts
Chapter 7 5
Gases, Sugar, and Water CycleGases, Sugar, and Water Cycle
Production of carbon compounds like Production of carbon compounds like glucose (photosynthesis) is linked with glucose (photosynthesis) is linked with energy extraction (in cellular respiration)energy extraction (in cellular respiration)
Water, COWater, CO22, sugar, and O, sugar, and O22 cycle between the cycle between the two processestwo processes
Photosynthesis and cellular respiration are Photosynthesis and cellular respiration are interconnectedinterconnected
Chapter 7 6Interconnections:Interconnections:Photosynthesis & RespirationPhotosynthesis & Respiration
Chapter 7 7
Adaptations for PhotosynthesisAdaptations for Photosynthesis
LeavesLeavesChloroplastsChloroplasts
Let’s look at your diagramsLet’s look at your diagrams
Chapter 7 8Structures ofStructures ofPhotosynthesisPhotosynthesis
Chapter 7 9
LeavesLeaves
Flattened leaf shape exposes large Flattened leaf shape exposes large surface area to catch sunlightsurface area to catch sunlight
Upper and lower leaf surfaces of a leaf Upper and lower leaf surfaces of a leaf comprise the comprise the epidermisepidermis
Waxy, waterproof Waxy, waterproof cuticlecuticle on outer on outer surfaces reduces water evaporationsurfaces reduces water evaporation
Chapter 7 10
Leaf AnatomyLeaf Anatomy
Adjustable pores called Adjustable pores called stomatastomata allow for allow for entry of air with COentry of air with CO22
Inner Inner mesophyllmesophyll cell layers contain cell layers contain majority of chloroplasts- many per cell majority of chloroplasts- many per cell “photosynthesis tissue”“photosynthesis tissue”
Vascular bundlesVascular bundles (veins) supply water (veins) supply water and minerals to the leaf while carrying and minerals to the leaf while carrying sugars away from the leafsugars away from the leaf
Chapter 7 11
Internal Leaf StructureInternal Leaf Structure
Internal leaf structure is crucial to Internal leaf structure is crucial to photosynthesis since photosynthesis photosynthesis since photosynthesis occurs primarily in the leaves of land occurs primarily in the leaves of land plans plans
Chapter 7 12
Leaf StructureLeaf Structure
MesophyllMesophyllCellsCells
MesophyllMesophyllCellsCells
Upper EpidermisUpper EpidermisUpper EpidermisUpper Epidermis
LowerLowerEpidermisEpidermis
LowerLowerEpidermisEpidermisVeinVeinVeinVein StomaStomaStomaStoma
Chapter 7 13
Anatomy of a ChloroplastAnatomy of a Chloroplast
Mesophyll cells have 40-200 Mesophyll cells have 40-200 chloroplasts eachchloroplasts each
Chloroplasts are bounded by a double Chloroplasts are bounded by a double membrane composed of the membrane composed of the innerinner and and outer membranesouter membranes
Chapter 7 14
Anatomy of a ChloroplastAnatomy of a Chloroplast
The The stromastroma is the semi-fluid medium within the is the semi-fluid medium within the inner membrane. Contains the enzymes needed inner membrane. Contains the enzymes needed for the reactions of photosynthesis. Location of for the reactions of photosynthesis. Location of light independent reactions of photosynthesis.light independent reactions of photosynthesis.
Disk-shaped sacs called Disk-shaped sacs called thylakoidsthylakoids found within found within the the stromastroma in stacks called in stacks called granagrana. Chlorophyll . Chlorophyll found in thylakoids. Involved in ATP synthesis or found in thylakoids. Involved in ATP synthesis or light dependent reactions of photosynthesislight dependent reactions of photosynthesis
Find these on YOUR diagramFind these on YOUR diagram
Chapter 7 15
Chloroplast StructureChloroplast Structure
Inner & OuterInner & OuterMembranesMembranes
ThylakoidsThylakoids
GranumGranum
Stroma Stroma (space)(space)
Chapter 7 16
REVIEW EQUATION FOR REVIEW EQUATION FOR PHOTOSYNTHESIS:PHOTOSYNTHESIS:
Chapter 7 17
End of Photosynthesis Lecture #2End of Photosynthesis Lecture #2Quiz tomorrow!!!!!Quiz tomorrow!!!!!
Chapter 7 18
Photosynthesis Lecture #3Photosynthesis Lecture #3Introduction to the light dependent Introduction to the light dependent reactions of photosynthesisreactions of photosynthesis
Chapter 7 19
In the light dependent reactions, the radiant In the light dependent reactions, the radiant energy from sunlight is used to make ATP energy from sunlight is used to make ATP and to reduce the electron acceptor and to reduce the electron acceptor molecule NADP+, forming NADPH. The molecule NADP+, forming NADPH. The light energy captured by photosynthesis is light energy captured by photosynthesis is temporarily stored within these two temporarily stored within these two compounds.compounds.
Chapter 7 20
Light dependent reaction equationLight dependent reaction equation
Water + NADP+ + ADP + P yieldsWater + NADP+ + ADP + P yieldsOxygen + NADPH + ATPOxygen + NADPH + ATP
How many of each??????How many of each??????
Chapter 7 21
Because life on our planet depends on light, Because life on our planet depends on light, it is important to understand the nature of it is important to understand the nature of light and how it permits photosynthesis to light and how it permits photosynthesis to occuroccur
Chapter 7 22
Light is a very small portion of a vast, Light is a very small portion of a vast, continuous spectrum of radiation called the continuous spectrum of radiation called the electromagnetic spectrum.electromagnetic spectrum.
Light travels in wavesLight travels in wavesA wavelength is the distance from one wave peak A wavelength is the distance from one wave peak
to the nextto the nextThe different colors of light correspond to The different colors of light correspond to
different regions of the visible spectrum and are different regions of the visible spectrum and are identified by their wavelengths. Violet light has identified by their wavelengths. Violet light has the shortest wavelength and red light has the the shortest wavelength and red light has the longestlongest
Chapter 7 23
Colors of the visible spectrumColors of the visible spectrum
ROY G BIVROY G BIV
Chapter 7 24
Chapter 7 25
The Energy in Visible LightThe Energy in Visible Light
The sun radiates The sun radiates electromagnetic energyelectromagnetic energyPackets of energy called Packets of energy called photonsphotons have have different energy different energy
levelslevels• Short-wavelength photons are very energeticShort-wavelength photons are very energetic• Longer-wavelength photons have lower energiesLonger-wavelength photons have lower energiesEnergy of photons is inversely proportional to the Energy of photons is inversely proportional to the
wavelength of lightwavelength of light
Chapter 7 26Light, ChloroplastLight, ChloroplastPigments, & PhotosynthesisPigments, & Photosynthesis
Gamma RaysGamma Rays X-RaysX-Rays UVUV InfraredInfrared Micro-Micro-waveswaves
RadioRadioWavesWaves
Visible LightVisible Light
400400 450450 500500 550550 600600 650650 700700 750750Wavelength (nanometers, nm)Wavelength (nanometers, nm)
• Photons interact with atomsPhotons interact with atoms• Raises electrons to higher energy levelsRaises electrons to higher energy levels• Excites or energizes the electronsExcites or energizes the electrons• When this occurs, one of two things can happen:When this occurs, one of two things can happen:
• Electron returns to original state and energy is Electron returns to original state and energy is lost as heat ORlost as heat OR
• The excited electron leaves the atom and is The excited electron leaves the atom and is accepted by the electron acceptor molecule. accepted by the electron acceptor molecule. (this is what occurs in Photosynthesis)(this is what occurs in Photosynthesis)
Chapter 7 27
PigmentsPigments
• Pigments are substances that absorb Pigments are substances that absorb visible lightvisible light
• Different pigments absorb different Different pigments absorb different wavelengths of lightwavelengths of light
Chapter 7 28
Chapter 7 29
Light Captured by PigmentsLight Captured by Pigments
Action of light-capturing pigmentsAction of light-capturing pigments• AbsorptionAbsorption of certain wavelengths of certain wavelengths
(light is “trapped”)(light is “trapped”)• ReflectionReflection of certain wavelengths of certain wavelengths
(light bounces back). Light we see(light bounces back). Light we see• TransmissionTransmission of certain wavelengths of certain wavelengths
(light passes through)(light passes through)
Chapter 7 30
Light Captured by PigmentsLight Captured by Pigments
Absorbed light drives biological processes Absorbed light drives biological processes when it is converted to chemical energywhen it is converted to chemical energy
Common pigments found in chloroplasts Common pigments found in chloroplasts include:include:• ChlorophyllChlorophyll aa andand b- absorbs light in the b- absorbs light in the
blue and red regions. Green NOT absorbedblue and red regions. Green NOT absorbed• Accessory pigments such as Accessory pigments such as carotenoids- carotenoids-
yellow and orangeyellow and orange
Chapter 7 31
Light Captured by PigmentsLight Captured by Pigments
Chlorophyll a and bChlorophyll a and b absorb violet, blue, absorb violet, blue, and red light but reflect green light and red light but reflect green light (hence they appear green)(hence they appear green)
CarotenoidsCarotenoids absorb blue and green light absorb blue and green light but reflect yellow, orange, or red (hence but reflect yellow, orange, or red (hence they appear yellow-orange)they appear yellow-orange)
Pigment absorbs visible lightPigment absorbs visible light
Chapter 7 32
00
2020
4040
6060
8080
100100
% L
ight
Abs
orpt
ion
% L
ight
Abs
orpt
ion
400400 450450 500500 550550 600600 650650 700700 750750Wavelength (nanometers)Wavelength (nanometers)
400400 450450 500500 550550 600600 650650 700700 750750
Absorption SpectraAbsorption Spectra
Visible LightVisible Light
ChlorophyllChlorophyll
CarotenoidsCarotenoids
PhycocyaninPhycocyanin
CollectivelyCollectively
Chapter 7 8Light, ChloroplastLight, ChloroplastPigments & PhotosynthesisPigments & Photosynthesis
Gamma RaysGamma Rays XX-- RaysRays UVUV InfraredInfrared MicroMicro--waveswaves
RadioRadioWavesWaves
Visible LightVisible Light
400400 400400 400400 400400 400400 400400 400400 400400Wavelength (nanometers)Wavelength (nanometers)
QuestionQuestion
Why do leaves “change color” in the fall??Why do leaves “change color” in the fall??
Chapter 7 33
AnswerAnswer
Leaves change color due to a lack of chlorophyll. Chlorophyll is used in photosynthesis and gives leaves their green color. As the days shorten, trees stop producing chlorophyll, allowing other pigments to take over
Chapter 7 34
ChromatographyChromatography
Activity completed hereActivity completed here
Chapter 7 35
Lecture #4Lecture #4Light Dependent Reactions of Light Dependent Reactions of PhotosynthesisPhotosynthesis
Chapter 7 36
Chapter 7 37
GlucoseGlucose
OO22
Overview of PhotosynthesisOverview of Photosynthesis
Light-DependentLight-DependentReactionsReactions
(in thylakoids)(in thylakoids)
Light-IndependentLight-IndependentReactionsReactions
(in stroma)(in stroma)
DepletedDepletedCarriersCarriers
(ADP, NADP(ADP, NADP++))
DepletedDepletedCarriersCarriers
(ADP, NADP(ADP, NADP++))
EnergizedEnergizedCarriersCarriers
(ATP, NADPH)(ATP, NADPH)
HH22OO
COCO22
2 phases of photosynthesis2 phases of photosynthesis
Photosynthesis happens in two phases:Photosynthesis happens in two phases:1.1. the light dependent reactions which the light dependent reactions which convert light energy into chemical energy convert light energy into chemical energy (produces ATP)(produces ATP)2.2. the light independent reactions- the light independent reactions- produce simple sugars from the ATP of the produce simple sugars from the ATP of the light dependent reactionslight dependent reactions
Chapter 7 38
Light dependent reactionsLight dependent reactions
• OVERVIEW:OVERVIEW:• Occurs in thylakoid membranes of Occurs in thylakoid membranes of
chloroplastchloroplast• Requires sunlight and waterRequires sunlight and water• Includes photosystems II and I and the Includes photosystems II and I and the
electron transport chainelectron transport chain• End products are ATP, NADPH, and End products are ATP, NADPH, and
oxygenoxygen
Chapter 7 39
NADPHNADPH
Nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide phosphatephosphate
Energy storage compound similar to ATPEnergy storage compound similar to ATP““electron acceptor”electron acceptor”Donates electrons for use in the Calvin Donates electrons for use in the Calvin Cycle (light independent reactions, or Cycle (light independent reactions, or “dark” reactions)“dark” reactions)
Chapter 7 40
Chapter 7 41The PhotosystemsThe Photosystems
Chapter 7 42
Light-Dependent ReactionsLight-Dependent Reactions
Steps of the light reactions: Steps of the light reactions: PHOTOSYSTEM IIPHOTOSYSTEM II
Accessory pigments in Photosystems Accessory pigments in Photosystems absorb light and pass the energy of absorb light and pass the energy of the light to the light to reaction centersreaction centers containing containing chlorophyllchlorophyll
Reaction centers receive energized Reaction centers receive energized electrons…electrons…
Chapter 7 43
Light-Dependent ReactionsLight-Dependent Reactions
Energized electrons then passed down a Energized electrons then passed down a series of electron carrier molecules series of electron carrier molecules ((Electron Transport ChainElectron Transport Chain). The ETC is a ). The ETC is a series of proteins embedded in the series of proteins embedded in the thylakoid membrane. Page 226thylakoid membrane. Page 226
Energy released from passed electrons used Energy released from passed electrons used to synthesize to synthesize ATPATP from ADP and from ADP and phosphatephosphate
Chapter 7 44
• After the electrons have traveled down After the electrons have traveled down the ETC, they are re-energized in a the ETC, they are re-energized in a second photosystem and passed down a second photosystem and passed down a second ETCsecond ETC
• Second photosystem is named Second photosystem is named PHOTOSYSTEM I PHOTOSYSTEM I
Chapter 7 45
PHOTOSYSTEM IPHOTOSYSTEM I
• At the bottom of this second ETC, the electrons are At the bottom of this second ETC, the electrons are still very energizedstill very energized
• The electrons are transferred to the stroma of the The electrons are transferred to the stroma of the chloroplast by an electron carrier molecule called chloroplast by an electron carrier molecule called NADP+NADP+
• NAPH+ combines with two electrons and one H+ to NAPH+ combines with two electrons and one H+ to become NADPHbecome NADPH
• NADPH stores the energy- does not use it. Energy NADPH stores the energy- does not use it. Energy will be used in the light independent reactionswill be used in the light independent reactions
Chapter 7 46
Steps (summary)Steps (summary)
Photosystem IIPhotosystem II1.1. Water and light inWater and light in2.2. Energized electrons (energy) passed to reaction centers containing chlorophyllEnergized electrons (energy) passed to reaction centers containing chlorophyll3.3. Oxygen releasedOxygen released4.4. Electron transport chain- proteins pass along electrons of H+Electron transport chain- proteins pass along electrons of H+
*#3 and #4 are known as PHOTOLYSIS when two molecules of water are split to form *#3 and #4 are known as PHOTOLYSIS when two molecules of water are split to form oxygen, H+, and electrons)oxygen, H+, and electrons)
Photosystem IPhotosystem I5. Light absorbed5. Light absorbed6. 26. 2ndnd ETC of H+ ETC of H+7.7. NADPH created in stromaNADPH created in stroma8.8. ATP synthetase creates ATP “Photophosphorylation”ATP synthetase creates ATP “Photophosphorylation”
NADPH and ATP fuel Calvin Cycle (otherwise known as light INDEPENDENT reaction)NADPH and ATP fuel Calvin Cycle (otherwise known as light INDEPENDENT reaction)
Chapter 7 47
Chapter 7 48Thylakoid Structure & Thylakoid Structure & Light-Dependent ReactionsLight-Dependent Reactions
Chapter 7 49
End lecture hereEnd lecture here
Chapter 7 50
PHOTOLYSISPHOTOLYSIS
• Reaction taking place in the thylakoid Reaction taking place in the thylakoid membranes of a chloroplast during light membranes of a chloroplast during light dependent reactions where two dependent reactions where two molecules of water are split to form molecules of water are split to form oxygen, hydrogen ions, and electronsoxygen, hydrogen ions, and electrons
Chapter 7 51
PHOTOLYSISPHOTOLYSIS
• Replaces the electrons lost at the Replaces the electrons lost at the beginning of photosystem II (first beginning of photosystem II (first photosystem)photosystem)
• Does this so chlorophyll can absorb Does this so chlorophyll can absorb additional light and continue producing additional light and continue producing ATPATP
• Figure 9.6 page 228Figure 9.6 page 228
Chapter 7 52
PHOTOLYSIS PHOTOLYSIS
• Equation page 228. Equation page 228. • KNOW itKNOW it
Chapter 7 53
PHOTOLYSISPHOTOLYSIS
• Products:Products:• ½ molecule of oxygen½ molecule of oxygen• Two electronsTwo electrons• Two hydrogen ionsTwo hydrogen ions
Chapter 7 54
PhotolysisPhotolysis
• Oxygen is released into the airOxygen is released into the air• Electrons are returned to chlorophyllElectrons are returned to chlorophyll• Hydrogen ions are pumped into thylakoid Hydrogen ions are pumped into thylakoid
where they accumulate high where they accumulate high concentrationconcentration
Chapter 7 55
Chapter 7 56
Oxygen as a By-productOxygen as a By-product
Chemiosmosis (2011-skip)Chemiosmosis (2011-skip)
• DEFINITION:DEFINITION:• Because there is a difference in Because there is a difference in
concentration of H+ on either side of the concentration of H+ on either side of the thylakoid membrane (creates a thylakoid membrane (creates a concentration gradient), ions diffuse out concentration gradient), ions diffuse out of the thylakoid and provide energy for of the thylakoid and provide energy for the production of ATP.the production of ATP.
• Page 228Page 228
Chapter 7 57
Chapter 7 58Chemiosmosis 1Chemiosmosis 1
Chapter 7 59
Chemiosmosis 2Chemiosmosis 2
Chemiosmosis animationChemiosmosis animation
http://www.youtube.com/watch?v=jHvXfplbS9Y
http://www.youtube.com/watch?v=E_XQR800AgM
Chapter 7 60
LIGHT INDEPENDENT REACTIONSLIGHT INDEPENDENT REACTIONSLecture #5Lecture #5
Chapter 7 61
Light Independent ReactionsLight Independent Reactions
OVERVIEWOVERVIEW• occurs in stroma (liquid portion of occurs in stroma (liquid portion of
chloroplast)chloroplast)• Involves the Calvin Cycle and carbon Involves the Calvin Cycle and carbon
fixationfixation• Sometimes referred to as “dark reaction”Sometimes referred to as “dark reaction”• Reactants- ATP, NADPH, carbon dioxideReactants- ATP, NADPH, carbon dioxide• End product- glucose End product- glucose
Chapter 7 62
Chapter 7 63
Light-Light-InIndependent Reactionsdependent Reactions
NADPH and ATP from light-dependent NADPH and ATP from light-dependent reactions used to power glucose reactions used to power glucose synthesissynthesis
Light not Light not directlydirectly necessary for light- necessary for light-independent reactions if ATP & NADPH independent reactions if ATP & NADPH availableavailable
Light-independent reactions called the Light-independent reactions called the Calvin-BensonCalvin-Benson CycleCycle or or CC33 Cycle Cycle
Chapter 7 64
The CThe C33 Cycle Cycle
6 CO6 CO22 used to synthesize 1 glucose used to synthesize 1 glucose (C(C66HH1212OO66))
Carbon dioxide is captured and linked to Carbon dioxide is captured and linked to ribulose bisphosphate (RuBP)ribulose bisphosphate (RuBP)
ATP and NADPH from light dependent ATP and NADPH from light dependent reactions used to power Creactions used to power C33 reactions reactions
Page 229 in your textPage 229 in your text
The calvin cycle takes the carbon in carbon The calvin cycle takes the carbon in carbon dioxide, adds it to one molecule of RuBP dioxide, adds it to one molecule of RuBP and forms sugars through a series of and forms sugars through a series of reactions in the stroma of chloroplasts. reactions in the stroma of chloroplasts. The NADPH and ATP produced during the The NADPH and ATP produced during the earlier light dependent reactions are earlier light dependent reactions are important molecules for this series of important molecules for this series of reactions.reactions.
Chapter 7 65
Question:Question:
Why is the calvin cycle in plants directly Why is the calvin cycle in plants directly and indirectly important to animals?and indirectly important to animals?
Chapter 7 66
Preview videoPreview video
http://www.youtube.com/watch?v=mYbMPwmwx88
Chapter 7 67
Chapter 7 68
CC33 Cycle Has Five Parts pg 229 Cycle Has Five Parts pg 229
1. Carbon fixation (carbon capture)1. Carbon fixation (carbon capture)• Carbon atom from carbon dioxide bonds Carbon atom from carbon dioxide bonds
with a five carbon sugar called ribulose with a five carbon sugar called ribulose biphosphate (RuBP) to form an unstable 6 biphosphate (RuBP) to form an unstable 6 carbon sugar. (six RuBP plus 6 CO2)carbon sugar. (six RuBP plus 6 CO2)
•Think of RuBP as carbonThink of RuBP as carbon dioxide dioxide acceptorsacceptors
Formation of three carbon Formation of three carbon moleculesmolecules
Step #2Step #2The six carbon sugar formed in step 1 immediately The six carbon sugar formed in step 1 immediately
splits to form two three carbon molecules called PGAsplits to form two three carbon molecules called PGA
Chapter 7 69
Use of ATP and NADPHUse of ATP and NADPH
Step #3Step #3A series of NADPH and ATP from the light A series of NADPH and ATP from the light dependent reactions converts the three dependent reactions converts the three carbon molecules into PGAL carbon molecules into PGAL (phosphoglyceraldehyde) which are 3 (phosphoglyceraldehyde) which are 3 carbon sugars with higher energy levelscarbon sugars with higher energy levels
Chapter 7 70
Sugar productionSugar production
Step 4Step 4One out of every six molecules of PGAL is One out of every six molecules of PGAL is transferred to the cytoplasm and used in transferred to the cytoplasm and used in the synthesis of sugars and other the synthesis of sugars and other carbohydrates. After THREE rounds of the carbohydrates. After THREE rounds of the cycle, (each round fixing one molecule of cycle, (each round fixing one molecule of CO2) CO2) six molecules of PGAL are produced.six molecules of PGAL are produced.
Chapter 7 71
RuBP is replenishedRuBP is replenished
Step 5Step 5Five molecules of PGAL, each with 3 carbon Five molecules of PGAL, each with 3 carbon atoms, produce three molecules of the five atoms, produce three molecules of the five carbon RuBP. This requires three more carbon RuBP. This requires three more ATP. This replenishes the RuBP that was ATP. This replenishes the RuBP that was used up, and the cycle can continue. The used up, and the cycle can continue. The 66thth molecule of PGAL is available to the molecule of PGAL is available to the organism to make sugar.organism to make sugar.
Chapter 7 72
• The PGAL that leaves the calvin cycle The PGAL that leaves the calvin cycle leaves the chloroplast and goes into the leaves the chloroplast and goes into the cytoplasmcytoplasm
• This PGAL can combine with another This PGAL can combine with another PGAL to form a 6 carbon sugar moleculePGAL to form a 6 carbon sugar molecule
• C6H12O6C6H12O6
Chapter 7 73
In summary, the imputs required for the In summary, the imputs required for the light independent reactions are 6 light independent reactions are 6 molecules of CO2, hydrogen from NADPH, molecules of CO2, hydrogen from NADPH, and ATP. In the end, the six carbons from and ATP. In the end, the six carbons from the CO2 can be accounted for by the the CO2 can be accounted for by the harvest of a six carbon molecule. The harvest of a six carbon molecule. The remaining PGAL molecules are used to remaining PGAL molecules are used to synthesize the RuBP molecules with which synthesize the RuBP molecules with which more CO2 molecules may combine.more CO2 molecules may combine.
Chapter 7 74
Calvin cycle animationCalvin cycle animation
http://www.youtube.com/watch?v=_NIhg1qa_L0
Chapter 7 75
Calvin cycle songCalvin cycle song
http://www.youtube.com/watch?v=_GpGGHGG6TU&feature=related
Chapter 7 76
Chapter 7 77
Relationship Between ReactionsRelationship Between Reactions
The “photo” part of photosynthesis The “photo” part of photosynthesis refers to the capture of light energy refers to the capture of light energy (light dependent reactions)(light dependent reactions)
The “synthesis” part of photosynthesis The “synthesis” part of photosynthesis refers to glucose synthesis (light-refers to glucose synthesis (light-inindependent reactions)dependent reactions)
Chapter 7 78
Relationship Between ReactionsRelationship Between Reactions
Light dependent reactions produce ATP Light dependent reactions produce ATP and NADPH which is used to drive and NADPH which is used to drive light-independent reactionslight-independent reactions
Depleted carriers (ADP and NADPDepleted carriers (ADP and NADP++) ) return to light-dependent reactions for return to light-dependent reactions for rechargingrecharging
Chapter 7 79
A Summary of PhotosynthesisA Summary of Photosynthesis
Light-dependent Light-dependent reactions occur reactions occur
in thylakoidsin thylakoids Light-Light-independent independent reactions (creactions (c33
cycle) occur in cycle) occur in stromastroma
Chapter 7 80
Lecture #6Lecture #6C3 and C4 plants and photorespirationC3 and C4 plants and photorespiration
Chapter 7 81
Chapter 7 82
Water, COWater, CO22, and the C, and the C44 Pathway Pathway
The ideal leaf:The ideal leaf:• has large surface area to intercept sunlighthas large surface area to intercept sunlight• are porous to allow for COare porous to allow for CO22 entry from air entry from air
Problem: Substantial leaf porosity leads to Problem: Substantial leaf porosity leads to substantial water evaporation, causing substantial water evaporation, causing dehydration stress on the plantdehydration stress on the plant
Plants evolved waterproof coating and Plants evolved waterproof coating and adjustable pores (stomata) for COadjustable pores (stomata) for CO22 entry entry
Chapter 7 83
When Stomata Are ClosedWhen Stomata Are Closed
When stomata close, COWhen stomata close, CO22 levels drop and O levels drop and O22 levels riselevels rise
Carbon fixing enzyme combines OCarbon fixing enzyme combines O22 instead of instead of COCO22 with RuBP (called with RuBP (called photorespirationphotorespiration))
Photorespiration:Photorespiration:• OO22 is used up as CO is used up as CO22 is generated is generated• No useful cellular energy madeNo useful cellular energy made• No glucose producedNo glucose produced• Photorespiration is unproductive and Photorespiration is unproductive and
wastefulwasteful
Chapter 7 84
When Stomata Are ClosedWhen Stomata Are Closed
Hot, dry weather causes stomata to stay Hot, dry weather causes stomata to stay closedclosed
Oxygen levels rise as carbon dioxide levels Oxygen levels rise as carbon dioxide levels fall inside leaffall inside leaf
Photorespiration very common under such Photorespiration very common under such conditionsconditions
Plants may die from lack of glucose Plants may die from lack of glucose synthesissynthesis
Chapter 7 85
CC44 Plants Reduce Photorespiration Plants Reduce Photorespiration
““CC44 plants” have chloroplasts in bundle plants” have chloroplasts in bundle sheath cells as well as mesophyll cellssheath cells as well as mesophyll cells• Bundle sheath cells surround vascular Bundle sheath cells surround vascular
bundles deep within mesophyllbundles deep within mesophyll• CC33 plants lack bundle sheath cell plants lack bundle sheath cell
chloroplastschloroplasts
Chapter 7 86
CC33 Plants & the Pathway Plants & the PathwayCC33 plants use the C plants use the C33
pathwaypathway
In a CIn a C33 plant, most plant, most chloroplasts are in chloroplasts are in
mesophyll cells.mesophyll cells.
Chapter 7 87
CC33 Plants & the Pathway Plants & the Pathway
Much photorespiration Much photorespiration occurs under hot, dry occurs under hot, dry
conditionsconditions
Chapter 7 88CC44 Plants & the C Plants & the C4 4 PathwayPathway
CC44 plants use the C plants use the C44 pathwaypathway
In a CIn a C44 plant, both plant, both mesophyll & bundle-mesophyll & bundle-sheath cells contain sheath cells contain
chloroplasts.chloroplasts.
Chapter 7 89
CC44 Plants & the Plants & the CC4 4 PathwayPathway
Almost no Almost no photorespiration photorespiration occurs under hot, occurs under hot,
dry conditions.dry conditions.
COCO22 is captured is captured with a highly with a highly
specific enzyme.specific enzyme.
Much glucose Much glucose synthesis occurs.synthesis occurs.
Mesophyll cell in a CMesophyll cell in a C44 plant plant
Bundle-sheath cell in a CBundle-sheath cell in a C44 plant plant
Photosynthesis songPhotosynthesis song
http://www.youtube.com/watch?v=Q_1mxZdF2TY
Chapter 7 90
Bozeman Biology PhotosynthesisBozeman Biology Photosynthesis
http://www.youtube.com/watch?v=_wO9f3ER17M
Chapter 7 91
Chapter 7Chapter 7
The endThe end