Photosynthesis is a major process which all should know. For this only this ppt has been made to understand the basics as well as more about it . It will help all students in their project submission. Hope find well. -LALIT KUMAR

1. PHOTOSYNTHESISPHOTOSYNTHESIS

2. *
PhotosynthesisPhotosynthesis
• AnabolicAnabolic (small molecules combined)(small molecules combined)
• EndergonicEndergonic (stores energy)(stores energy)
• Carbon dioxide (COCarbon dioxide (CO22)) requiring processrequiring process
that usesthat uses light energy (photons)light energy (photons) andand
water (Hwater (H22O)O) to produceto produce organicorganic
macromolecules (glucose).macromolecules (glucose).
6CO2 + 6H2O → C6H12O6 + 6O2glucoseglucose
SUN
photonsphotons

3. *
Question:Question:
Where doesWhere does
photosynthesisphotosynthesis
take place?take place?

4. *
PlantsPlants
• AutotrophsAutotrophs – produce their own food– produce their own food
(glucose)(glucose)
• Process calledProcess called photosynthesisphotosynthesis
• Mainly occurs in theMainly occurs in the leaves:leaves:
a.a. stoma - poresstoma - pores
b.b. mesophyll cellsmesophyll cells
Stoma
Mesophyll
Cell
Chloroplast

5. *
Stomata (stoma)Stomata (stoma)
PoresPores in a plant’s cuticle throughin a plant’s cuticle through
whichwhich water vaporwater vapor andand gasesgases (CO(CO22
& O& O22)) are exchanged between theare exchanged between the
plant and the atmosphere.plant and the atmosphere.
Guard CellGuard Cell
Carbon Dioxide
(CO2)
Oxygen
(O2)
Found on the underside of leavesFound on the underside of leaves
StomaStoma

6. *
Mesophyll Cell of LeafMesophyll Cell of Leaf
Cell Wall
NucleusNucleus
Chloroplast
Central Vacuole
Photosynthesis occurs in these cells!Photosynthesis occurs in these cells!

7. *
ChloroplastChloroplast
OrganelleOrganelle where photosynthesisphotosynthesis
takes place.
GranumThylakoid
Stroma
Outer Membrane
Inner Membrane
Thylakoid stacks are connected togetherThylakoid stacks are connected together

8. *
ThylakoidThylakoid
Thylakoid Membrane
Thylakoid Space
Granum
Grana make up the inner membraneGrana make up the inner membrane

9. *
Question:Question:
Why areWhy are
plantsplants
green?green?

10. *
Chlorophyll MoleculesChlorophyll Molecules
• Located in theLocated in the thylakoid membranesthylakoid membranes
• Chlorophyll haveChlorophyll have MgMg++
in the centerin the center
• Chlorophyll pigmentsChlorophyll pigments harvest energyharvest energy
(photons)(photons) by absorbing certainby absorbing certain
wavelengthswavelengths (blue-420 nm and red-(blue-420 nm and red-
660 nm660 nm are most important)are most important)
• Plants arePlants are greengreen because thebecause the greengreen
wavelength is reflectedwavelength is reflected, not absorbed, not absorbed.

11. *

12. *
Wavelength of Light (nm)Wavelength of Light (nm)
400 500 600 700
Short wave Long wave
(more energy) (less energy)

13. *
Absorption of Light byAbsorption of Light by
ChlorophyllChlorophyll
wavelengthwavelength
Absorption
violet blue green yellow orange red
Chlorophyll absorbs blue-violet & red light bestChlorophyll absorbs blue-violet & red light best

14. *
Question:Question:
During the fall,During the fall,
what causes thewhat causes the
leaves to changeleaves to change
colors?colors?

15. *
Fall ColorsFall Colors
• In addition to the chlorophyllIn addition to the chlorophyll
pigments, there arepigments, there are other pigmentsother pigments
presentpresent
• During the fall, theDuring the fall, the greengreen
chlorophyll pigments are greatlychlorophyll pigments are greatly
reducedreduced revealing the other pigmentsrevealing the other pigments
• CarotenoidsCarotenoids are pigments that areare pigments that are
eithereither redred,, orangeorange, or, or yellowyellow

16. *
Redox ReactionRedox Reaction
TheThe transfertransfer of one or moreof one or more
electronselectrons from one reactant tofrom one reactant to
anotheranother
Two types:Two types:
1.1. Oxidation is theOxidation is the lossloss of eof e--
2.2. Reduction is theReduction is the gaingain of eof e--

17. *
Oxidation ReactionOxidation Reaction
TheThe loss of electronsloss of electrons from afrom a
substance or thesubstance or the gain ofgain of
oxygen.oxygen.
glucoseglucose
6CO2 + 6H2O → C6H12O6 + 6O2
OxidationOxidation
CarbonCarbon
dioxidedioxide WaterWater
OxygenOxygen

18. *
Reduction ReactionReduction Reaction
TheThe gain of electronsgain of electrons to ato a
substance or thesubstance or the loss ofloss of
oxygen.oxygen.
glucoseglucose
6CO2 + 6H2O → C6H12O6 + 6O2
ReductionReduction

19. *
Question:Question:
Why do cellsWhy do cells
use foruse for
energy?energy?

20. *
Energy for Life on EarthEnergy for Life on Earth
• Sunlight is the ULTIMATE
energy for all life on Earth
• Plants store energy in the
chemical bonds of sugars
• Chemical energy is released as
ATP during cellular respiration

21. *
Structure of ATPStructure of ATP
• ATP stands for adenosine
triphosphate
• It is composed of the nitrogen base
ADENINE, the pentose (5C) sugar
RIBOSE, and three PHOSPHATE
groups
• The LAST phosphate group is bonded
with a HIGH ENERGY chemical bond
• This bond can be BROKEN to release
ENERGY for CELLS to use

22. *
Removing a Phosphate from ATPRemoving a Phosphate from ATP
Breaking the LAST PHOSPHATE bond
from ATP, will ---
– Release ENERGY for cells to use
– Form ADP
– Produce a FREE PHOSPHATE GROUP

23. *
High Energy Phosphate BondHigh Energy Phosphate Bond

24. *
FREE PHOSPHATE can be re-attached toFREE PHOSPHATE can be re-attached to
ADP reforming ATPADP reforming ATP
Process calledProcess called PhosphorylationPhosphorylation

25. *
PhosphorylationPhosphorylation

26. *
Parts ofParts of
PhotosynthesisPhotosynthesis

27. *
Two Parts of PhotosynthesisTwo Parts of Photosynthesis
Two reactions make upTwo reactions make up
photosynthesis:photosynthesis:
1.1.Light Reaction or LightLight Reaction or Light
Dependent ReactionDependent Reaction --
Produces energy from solarProduces energy from solar
power (photons) in the form ofpower (photons) in the form of
ATP and NADPH.ATP and NADPH.
SUNSUN

28. *
Two Parts of PhotosynthesisTwo Parts of Photosynthesis
2.2. Calvin Cycle or LightCalvin Cycle or Light
IndependentIndependent
ReactionReaction
• Also calledAlso called Carbon FixationCarbon Fixation
oror CC33 FixationFixation
• Uses energy (Uses energy (ATP andATP and
NADPHNADPH) from light reaction) from light reaction
to make sugarto make sugar (glucose).(glucose).

29. *
Light Reaction (Electron Flow)Light Reaction (Electron Flow)
• Occurs in theOccurs in the ThylakoidThylakoid
membranesmembranes
• During theDuring the light reactionlight reaction, there, there
areare twotwo possible routes forpossible routes for
electron flow:electron flow:
A.A.Cyclic Electron FlowCyclic Electron Flow
B.B. Noncyclic Electron FlowNoncyclic Electron Flow

30. *
Cyclic Electron FlowCyclic Electron Flow
• Occurs in theOccurs in the thylakoidthylakoid membrane.membrane.
• UsesUses Photosystem I onlyPhotosystem I only
• P700P700 reaction center- chlorophyll areaction center- chlorophyll a
• Uses Electron Transport ChainUses Electron Transport Chain
(ETC)(ETC)
• GeneratesGenerates ATP onlyATP only
ADP +ADP + ATPATP
P

31. *
Cyclic Electron FlowCyclic Electron Flow
P700
Primary
Electron
Acceptor
e-
e-
e-
e-
ATPATP
produced
by ETC
Photosystem I
Accessory
Pigments
SUN
Photons
Pigments absorb light energy & excite e- ofPigments absorb light energy & excite e- of
Chlorophyll a to produce ATPChlorophyll a to produce ATP

32. *
Noncyclic Electron FlowNoncyclic Electron Flow
• Occurs in theOccurs in the thylakoidthylakoid membranemembrane
• UsesUses Photosystem IIPhotosystem II andand
Photosystem IPhotosystem I
• P680P680 reaction centerreaction center (PSII)(PSII) --
chlorophyll achlorophyll a
• P700P700 reaction centerreaction center (PS I)(PS I) --
chlorophyll achlorophyll a
• Uses Electron Transport ChainUses Electron Transport Chain
(ETC)(ETC)
• GeneratesGenerates OO22, ATP and NADPH, ATP and NADPH

33. *
Noncyclic Electron FlowNoncyclic Electron Flow
P700
Photosystem I
P680
Photosystem II
Primary
Electron
Acceptor
Primary
Electron
Acceptor
ETC
Enzyme
Reaction
H2O
1/2O1/2O22 + 2H+
ATPATP
NADPHNADPH
Photon
2e-
2e-
2e-
2e-
2e-
SUN
Photon
HH22O is split in PSII & ATP is made, while the energy carrierO is split in PSII & ATP is made, while the energy carrier
NADPH is made in PSINADPH is made in PSI

34. *
Noncyclic Electron FlowNoncyclic Electron Flow
• ADP +ADP + →→ ATPATP
• NADPNADP++
+ H+ H →→ NADPHNADPH
• OxygenOxygen comes from the splittingcomes from the splitting
of Hof H22O, not COO, not CO22
HH22OO →→ 1/2 O1/2 O22 + 2H+ 2H++
PP

35. *
ChemiosmosisChemiosmosis
• PowersPowers ATP synthesisATP synthesis
• Takes place across the thylakoidTakes place across the thylakoid
membranemembrane
• UsesUses ETCETC andand ATP synthaseATP synthase
(enzyme)(enzyme)
• H+H+ move down their concentrationmove down their concentration
gradient throughgradient through channels of ATPchannels of ATP
synthasesynthase formingforming ATP from ADPATP from ADP

36. *
ChemiosmosisChemiosmosis
H+
H+
ATP Synthase
H+
H+ H+
H+
H+
H+
high Hhigh H++
concentrationconcentration
H+
ADP + P ATP
PS II PS I
E
T
C
low Hlow H++
concentrationconcentration
H+
ThylakoidThylakoid
SpaceSpace
ThylakoidThylakoid
SUN
(Proton Pumping)

37. *
Calvin CycleCalvin Cycle
• Carbon FixationCarbon Fixation (light independent(light independent
reaction)reaction)
• CC33 plants (80% of plants on earth)plants (80% of plants on earth)
• Occurs in theOccurs in the stromastroma
• UsesUses ATP and NADPHATP and NADPH from lightfrom light
reaction as energyreaction as energy
• UsesUses COCO22
• To produceTo produce glucoseglucose: it takes: it takes 66
turns and uses 18 ATP and 12turns and uses 18 ATP and 12
NADPH.NADPH.

38. *
ChloroplastChloroplast
GranumThylakoid
STROMA– where Calvin Cycle occurs
Outer Membrane
Inner Membrane

39. *
Calvin Cycle (CCalvin Cycle (C33 fixation)fixation)
6CO2
6C-C-C-C-C-C
6C-C-C 6C-C-C
6C-C-C-C-C
12PGA
RuBP
12G3P
(unstable)
6NADPH 6NADPH
6ATP 6ATP
6ATP
C-C-C-C-C-C
Glucose
(6C)
(36C)
(36C)
(36C)
(30C)
(30C)
(6C)
6C-C-C 6C-C-C
C3
glucose

40. *
Calvin CycleCalvin Cycle
Remember: CRemember: C33 = Calvin Cycle= Calvin Cycle
C3
Glucose

41. *
PhotorespirationPhotorespiration
• Occurs on hot, dry, bright daysOccurs on hot, dry, bright days
• Stomates closeStomates close
• Fixation of OFixation of O22 instead of COinstead of CO22
• ProducesProduces 2-C molecules instead of2-C molecules instead of
3-C sugar molecules3-C sugar molecules
• ProducesProduces no sugarno sugar molecules ormolecules or nono
ATPATP

42. *
PhotorespirationPhotorespiration
Because of photorespiration, plantsBecause of photorespiration, plants
have special adaptations to limithave special adaptations to limit
the effect of photorespiration:the effect of photorespiration:
1.1. CC44 plantsplants
2.2. CAM plantsCAM plants

43. *
CC44 PlantsPlants
• Hot, moistHot, moist
environmentsenvironments
• 15% of plants15% of plants
((grasses, corn,grasses, corn,
sugarcane)sugarcane)
• PhotosynthesisPhotosynthesis
occurs in 2 placesoccurs in 2 places
• Light reactionLight reaction --
mesophyll cellsmesophyll cells
• Calvin cycleCalvin cycle - bundle- bundle
sheath cellssheath cells

44. *
CC44 PlantsPlants
Mesophyll CellMesophyll Cell
CO2
C-C-C
PEP
C-C-C-C
Malate-4C sugar
ATP
Bundle Sheath CellBundle Sheath Cell
C-C-C
Pyruvic Acid
C-C-C-C
CO2
C3
Malate
Transported
glucose
Vascul
Tissu

45. *
CAM PlantsCAM Plants
• Hot, dry environmentsHot, dry environments
• 5%5% of plants (cactus and iceof plants (cactus and ice
plants)plants)
• Stomates closed during dayStomates closed during day
• Stomates open during the nightStomates open during the night
• Light reaction - occurs duringLight reaction - occurs during
the daythe day
• Calvin Cycle - occurs when COCalvin Cycle - occurs when CO22 isis
presentpresent

46. *
CAM PlantsCAM Plants
Night (Stomates Open) Day (Stomates Closed)
Vacuole
C-C-C-C
Malate
C-C-C-C
Malate Malate
C-C-C-C
CO2
CO2
C3
C-C-C
Pyruvic acid
ATP
C-C-C
PEP
glucose

47. *
Question:Question:
Why do CAMWhy do CAM
plants closeplants close
their stomatatheir stomata
during the day?during the day?

48. Cam plants closeCam plants close
their stomata intheir stomata in
the hottest partthe hottest part
of the day toof the day to
conserve waterconserve water