The document provides an overview of photosynthesis, explaining its definition, requirements, and importance as a fundamental process for life on Earth. It details the mechanisms involved, including light and dark reactions, photosystems, and pathways such as the Calvin cycle, C4 pathway, and CAM pathway, as well as the roles of various pigments. The document also addresses photorespiration and its implications for certain plant types under stress conditions.

1. REVISION SESSION
PHOTOSYNTHESIS
BOTANY INSIDER

2. • CHECK AUDIO AND VIDEO....

3. WHAT IS PHOTOSYNTHESIS?
Photo + Synthesis
LIGHT TO MAKE
To make something using light ..

4. OCCURS IN:
• Photosynthetic organisms :
PLANTS ALGAE
SOME BACTERIA ETC.

5. • Photosynthesis is a process in
which photosynthetic organisms
use light energy to
make(synthesize) organic
compounds .

6. • It is a PHYSIOCHEMICAL process.
Means, both physical and chemical factors are being
used in the process.
It is - anabolic process.

7. REQUIREMENTS
• WATER
• SUNLIGHT
• CARBON DIOXIDE
• CHLOROPHYLL-GREEN PIGMENT

8. •CHEMICAL REACTION:

10. Importance :
• BASIS OF LIFE ON EARTH...????
• PRIMARY SOURCE OF FOOD ON EARTH.

11. • MAINTAIN OXYGEN EQUILIBRIUM IN
ENVIRONMENT.
ALSO MAKES-RESERVE OF ENERGY TO MAN AS- FUEL
(COAL,OIL,WOOD ETC..)

12. PHOTOSYNTHESIS
PART-2

13. PHOTOSYNTHETIC APPARATUS :
•CHLOROPLAST

14. ABOUT CHLOROPLAST
• SHAPE- DISCOID OR ELLIPOSIDAL
• SIZE- 4-6 μ (meu) in length
• THICKNESS- 1-2 μ (meu)
• STRUCTURE- Double membraned (300 A)
• EACH MEMBRANE – 50 A
» MADE OF LIPIDS BILAYER AND PROTEINS

16. PHOTOSYNTHETIC PIGMENTS
3 TYPES
CHLOROPHYLL
CAROTENOIDS
PHYCOBILINS

17. CHLOROPHYHLL

18. STRUCTURE
• Magnesium porphyrin compound
• Contains 4 pyrrol ring-joined by –CH bridges.
• Long chain of C atom- called PHYTOL.
Attached to PORPHYRIN RING AT
4TH PYRROL RING

20. DERIVATION
GLUTAMATE
Trna GLUTAMATE
-AMINO EVULENIC ACID
PROTOPORPHYRIN DERIVATIVE
CHLOROPHYLL

21. MOLECULAR FORMULA
• CHLOROPHYLL A
•CHLOROPHYLL B

22. FORMATION
PROTOCHLOROPHYLL
NADPH LIGHT
Protochlorophyll oxidoreductase 2H
CHLOROPHYLL

23. CAROTENOIDS
• These are pigments in plants, algae, and photosynthetic
bacteria.
• Produce the bright yellow, red, and orange colors in
plants, vegetables, and fruits.
• CANNOT TRANSFER ENERGY DIRECTLY TO
PHOTOSYNTHETIC PATHWAY .

24. • CAROTENOIDS INCLUDE
• CAROTENES XANTHOPHYLLS

25. • NOTE 1.-
» LYCOPENE-
• Chief pigment of tomato fruit.

26. • NOTE 2-
• In autumn – chlorophyll is degraded
• Leads to unmasking – the more stable
carotenoid pigment.
• Gives bright yellow or orange colour

27. PHYCOBILINS
• Contain OPEN conjugated system of 4 Pyrrol ring.
• Lacks Mg and Phytol tail.
• Water soluble.
• Found in stroma.
• OCCUR ONLY IN CYANOBACTERIA AND
RHODOPHYTA.

28. RED DROP AND EMERSON
ENHANCEMENT EFFECT.

29. QUANTUM REQUIREMENT :
• The number of photons or quanta required to release
one molecule of oxygen in photosynthesis.
QUANTUM YIELD:
• The number of oxygen molecule released per photon of
light in photosynthesis.

30. ABOUT
• BY- ROBERT EMERSON AND LEWIS
• Experiment - determining the quantum yield of
photosynthesis in Chlorella – using monochromatic light of
different wavelength.
Sharp decline in quantum yield
At wavelength greater than 680nm
red part of spectrum.
THUS THE PHENOMENON CALLED –RED
DROP

32. EMERSON ENHANCEMENT EFFECT

33. • RESULT-
• CHLORELLA when treated with a wavelength of
range 680-700nm – maximum quantum yield
obtained .
• There are 2 photosystems(PS) present
» PS I PS II
(700nm) (680 nm)

34. PHOTOSYSTEMS

35. ABOUT
• Presence of Photosystems -suggested by
Red drop and Emerson enhancement effect.
- Major role in photosynthesis.
- These are groups of photosynthetic pigments.

36. • Each PHOTOSYSTEM (PS) contain –
Central core Light harvesting
complex complex
Contain reaction centers contain antenna pigments
associated with proteins associated with proteins.
and e- donor and acceptor

37. PHOTOSYSTEM I
• Relatively very weakly fluroscent.
• Contain – chlorophyll-b
- chlorophyll-a (many forms).
Absorbs 700nm wavelength of light.
Contain 18 subunits.
Proteins- Psa A - molecular mass: 66-70kDa
- Psa B

38. PHOTOSYSTEM II
• Strongly fluorescent
• Contain – chlorophyll-a (some forms)
- chlorophyll-b
• Absorbs – 680 nm of wavelength.
• Proteins- D1 CSIR-NET QUESTION
- D2
(THESE ARE LARGE MEMBRANE PROTEINS).
-localised in stacked region of thylakoid membrane.

39. PHOTOSYNTHESIS(part-4)

40. MECHANISM OF PHOTOSYNTHESIS
• Oxidation- reduction process
water carbon dioxide
ENDOTHERMIC
PROCESS

41. • PHOTOSYNTHESIS IS A TWO STAGE PROCESS:
A. LIGHT REACTION
(LIGHT DEPENDENT REACTION)
B.DARK REACTION
(LIGHT INDEPENDENT REACTION)

42. • LIGHT REACTION-
• GRANA
• DARK REACTION-
• STROMA

45. PHOTOSYNTHESIS (part-5)

46. LIGHT REACTION
• OCCURS ONLY IN THE PRESENCE OF LIGHT
• LOCATION: GRANA (THYLAKOID)
• REQUIRES: NADPH and ATP
• ALSO CALLED – THYLAKOID REACTION
- PHOTOPHOSPHORYLATION.

47. LIGHT REACTION
(PHOTOPHOSPHORYLATION )
(PHOTOCHEMICAL REACTION)
NON-CYCLIC
PHOTOPHOSPHORYLATION
CYCLIC
PHOTOPHOSPHORYLATION

48. STEPS
• Absorption of light energy by chloroplast pigments
• Transfer of light energy from accessory pigments to
chlorophyll-a .
• Activation of chlorophyll-a by photon of light.
• Photolysis of water and oxygen evolution.
• Electron transport and production of assimilatory
power(NADPH, ATP)

49. PHOTOLYSIS OF WATER
• Breakdown of water in the presence of light.
• Occurs via: WATER SPLITTING COMPLEX OR
OXYGEN EVOLVING COMPLEX(PS II)
ESSENTIALS : Mn2+, Cl-, Ca2+ CSIR-UGC-NET

50. Z-SCHEME
• Light induced electron transport.
• Involves PS I and PS II
• ELECTRONS move from water through PS II to PS I and
then to NADP+
• Electron transport leads to – proton motive
force generation
- ATP synthesis

51. Pheo
ATP

52. Products
• ATP produced
• NADPH produced

53. ATP
ATP

54. NON-CYCLIC
PHOTOPHOSPHORYLATION
•Involves both PS I and
PS II
•Photolysis of water
•Formation of oxygen
•1 ATP synthesis
•NADPH synthesis
CYCLIC PHOTOPHOSPHORYLATION
•Involves only PS I
•No photolysis of water
•No formation of
oxygen
•2 ATP synthesis
•No NADPH synthesis

55. PHOTOSYNTHESIS (part-6)

56. CALVIN CYCLE
PHOTORESPIRATION
CSIR-NET QUESTION
DARK REACTION

57. CALVIN CYCLE
• By-Melvin Calvin in 1957
• Also called C3 CYCLE – first stable product-
PGA (3C)
• Light independent reaction
• Require products of light reaction.
• REDUCTIVE-PENTOSE PHOSPHATE PATHWAY
• REQUIRES -ATP
NADPH CO2
Location – STROMA

58. RUBISCO
• Ribulose-1,5-bisphosphate carboxylase-oxygenase
• Can work as both oxygenase and carboxygenase
• Equal affinity for OXYGEN and CARBON DIOXIDE
• Same active site for both.
• Activity depends on concentration

59. CONDITIONS
• Moderate temperature
• Moderate light CSIR –NET
• High concentration of CO2

60. IMPORTANT

61. PHOTORESPIRATION
• C2 cycle – first stable product-2C
PHOSPHOGLYCOLATE
• HARMFUL PROCESS- UNFIXES fixed CO2
• OCCURS WHEN – C3 plant –encounter STRESS.
• Example- Wheat, beans, plants in temperate areas .

62. CONDITIONS
• High temperature
• High concentration of oxygen
• Less CO2 (less than 50ppm)
hence, RUBISCO works
as OXYGENASE
CSIR –NET

63. IMPORTANT
Glycolate

64. PHOTOSYNTHESIS (part-7)

65. C4- PATHWAY
CAM PATHWAY

66. C4 PATHWAY
• HATCH SLACK PATHWAY.
• Called C4 cycle- first stable product
OAA(oxaloacetate)
• Occurs in – plants – temperate region –to avoid
photorespiration.
• Example- maize, sorghum,sugarcane,corn.
• Adaptations – Dimorphic chloroplast
- Kranz anatomy

67. Agranal – Bundle
sheath cells
Granal- Mesophyll
cell
Kranz-wreath like –circular manner.
Adaptations

69. CAM PATHWAY
• Crassulacean acid metabolism
• Occurs in plants –growing in DRY areas
• Example- succulent and xerophytes.
• Adaptation – SCOTOACTIVE stomata
Stomata remain open at NIGHT.
• Leads to less water loss.

71. CSIR -NET QUESTION
ANSWER -A

72. •PHOTOSYNTHESIS
COMPLETED.

73. TELEGRAM CHANNEL- BOTANY INSIDER
•LIKE
•SHARE
•SUBSCRIBE