• Almost all plants are photosynthetic autotrophs,
– Autotrophs generate their own organic matter through
photosynthesis
–...
6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
WHYWHY AREARE PLAPLANTSNTS GREGREEN?EN?
Plant Cells
have Green
Chloroplasts
The thylakoid
membrane of the
chloroplast is
i...
• Photosynthesis is the process by which
autotrophic organisms use light energy to
make sugar and oxygen gas from carbon
d...
• Chloroplasts absorb
light energy and
convert it to
chemical energy
through a serious of
reactions that occur
in chloropl...
Types of reactions
Light Reaction
(Hill reaction)
Dark Reaction
The reactions of
photosynthesis that occur
in the presence...
• To understand photosynthesis let us know
the reactions that occur in the presence of
light. i:e Oxidation and reduction ...
• When a substance is oxidised the hydrogen and
electrons removed from this substances are
transformed to another substanc...
• These acceptors which accept electrons
are called ELECTRON ACCEPTORS.
• Eg:
Ferridoxins
Adenine dinucleotide ( NAD)
Nico...
Mechanism of photosynthesis
1.During Ps Chlorophyll molecule traps solar energy and gets oxidized
• When light falls on th...
2.Chlorophyll splits water molecule and gets back its electron from water
• With the removal of electron, chlorophyll is i...
3.ATP AND NADPH are formed during photosynthesis
• Protons (derived from splitting of water molecule) are left behind are
...
Light
NADPH
OH-
2 H+
CARBOHYDRATES
Co2
½ O2NADP
Formation of carbohydrates and NADPH
1.3.2 The Dark reaction or
Carbon fixation
• Co2 Glucose in a series of
reactions that occur in stroma(Chloroplast).
• ATP...
Calvin Cycle
6 Co2 ( 1 mol)
6 Ribulose 1, 5 Di phosphate
6 Hexose Sugar 1,5 Diphosphate
2 PGA
Glyceraldehyde 3 – Phosphate...
2 H+
+ OH - 1
/2
Water-splitting
photosystem
Reaction-
center
chlorophyll
Light
Primary
electron
acceptor
Energy
to make
E...
• The production of ATP by chemiosmosis in
photosynthesis
Thylakoid
compartment
(high H+
)
Thylakoid
membrane
Stroma
(low ...
• The Calvin cycle makes
sugar from carbon
dioxide
– ATP generated by the light
reactions provides the energy
for sugar sy...
PHOTOSYNTHESIS
• Sunlight provides
ENERGY
CO2 + H2O produces
Glucose + Oxygen
6CO2 + 6H2O
C6H12O6 + 6O2
Steps of Photosynthesis
• Light hits reaction centers of
chlorophyll, found in chloroplasts
• Chlorophyll vibrates and cau...
Steps of Photosynthesis
• The DARK Reactions= Calvin Cycle
• CO2 from atmosphere is joined to H
from water molecules (NADP...
• In most plants, photosynthesis occurs
primarily in the leaves, in the chloroplasts
• A chloroplast contains:
– stroma, a...
• The location and structure of chloroplasts
LEAF CROSS SECTION MESOPHYLL CELL
LEAF
Chloroplast
Mesophyll
CHLOROPLAST Inte...
• Chloroplasts contain several pigments
Chloroplast Pigments
– Chlorophyll a
– Chlorophyll b
– Carotenoids
– Xanthophyll
F...
Chlorophyll a & b
•Chl a has a methyl
group
•Chl b has a carbonyl
group
Porphyrin ring
delocalized e-
Phytol tail
Different pigments absorb light
differently
Cyclic Photophosphorylation
• Process for ATP generation associated with
some Photosynthetic Bacteria
• Reaction Center =>...
Photon
Photon
Water-splitting
photosystem
NADPH-producing
photosystem
ATP
mill
• Two types of
photosystems
cooperate in th...
Primary
electron acceptor
Primary
electron acceptor
Electron
transport chain
Electron
transport
Photons
PHOTOSYSTEM I
PHOT...
• The O2 liberated by photosynthesis is made
from the oxygen in water (H+
and e-
)
Plants produce OPlants produce O22 gas ...
• Two connected photosystems collect
photons of light and transfer the energy to
chlorophyll electrons
• The excited elect...
• The electron transport chains are arranged
with the photosystems in the thylakoid
membranes and pump H+
through that
mem...
Summary—Light Dependent
Reactions
a. Overall input
light energy, H2
O.
b. Overall output
ATP, NADPH, O2
.
• Animation is of the Calvin Cycle
Note what happens to the carbon dioxide
and what the end product is.
• Second animation...
Light Independent Reactions
aka Calvin Cycle
Carbon from CO2 is
converted to glucose
(ATP and NADPH
drive the reduction
of...
Light Independent Reactions
aka Calvin Cycle
CO2 is added to the 5-C sugar RuBP by the
enzyme rubisco.
This unstable 6-C c...
Summary—Light Independent
Reactions
a. Overall input
CO2
, ATP, NADPH.
b. Overall output
glucose.
Review: Photosynthesis uses light
energy to make food molecules
Light
Chloroplast
Photosystem II
Electron
transport
chains...
Types of Photosynthesis
C3
C4
CAM
Rubisco: the world’s busiest enzyme!
Competing Reactions
• Rubisco grabs CO2, “fixing” it into a
carbohydrate in the light independent
reactions.
• O2 can also...
Photorespiration
• When Rubisco reacts with O2 instead of
CO2
• Occurs under the following conditions:
– Intense Light (hi...
Why high heat?
• When it is hot, plants close their
stomata to conserve water
• They continue to do photosynthesis 
use u...
C4 Photosynthesis
• Certain plants have developed ways to
limit the amount of photorespiration
– C4 Pathway*
– CAM Pathway...
Leaf Anatomy
• In C3 plants (those that do C3
photosynthesis), all processes occur in the
mesophyll cells.
Image taken wit...
C4 Pathway
• In C4 plants
photosynthesis occurs
in both the mesophyll
and the bundle sheath
cells.
Image taken without per...
C4 Pathway
• CO2
is fixed into a 4-
carbon intermediate
• Has an extra
enzyme– PEP
Carboxylase that
initially traps CO2
in...
C4 Pathway
• The 4 carbon intermediate
is “smuggled” into the
bundle sheath cell
• The bundle sheath cell is
not very perm...
How does the C4 Pathway
limit photorespiration?
• Bundle sheath cells are far from the
surface– less O2 access
• PEP Carbo...
CAM Pathway
• Fix CO2
at night and
store as a 4 carbon
molecule
• Keep stomates
closed during day to
prevent water loss
• ...
How does the CAM Pathway
limit photorespiration?
• Collects CO2 at night so that it can be
more concentrated during the da...
Summary of C4
Photosynthesis
• C4 Pathway
– Separates by
space (different
locations)
• CAM Pathway
– Separates
reactions b...
 mechanism of photosysthesis PPT, SSC AP srinivas nallapu
 mechanism of photosysthesis PPT, SSC AP srinivas nallapu
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  • Affinity of PEP Carboxylase for CO2 is much higher than its affinity for O2.
  • mechanism of photosysthesis PPT, SSC AP srinivas nallapu

    1. 1. • Almost all plants are photosynthetic autotrophs, – Autotrophs generate their own organic matter through photosynthesis – Sunlight energy is transformed to energy stored in the form of chemical bonds (a) Mosses, ferns, and flowering plants (b) Kelp (c) Euglena (d) Cyanobacteria THE BASICS OF PHOTOSYNTHESIS
    2. 2. 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
    3. 3. WHYWHY AREARE PLAPLANTSNTS GREGREEN?EN? Plant Cells have Green Chloroplasts The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).
    4. 4. • Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water AN OVERVIEW OF PHOTOSYNTHESIS Carbon dioxide Water Glucose Oxygen gas PHOTOSYNTHESIS
    5. 5. • Chloroplasts absorb light energy and convert it to chemical energy through a serious of reactions that occur in chloroplast. • The reactions of photosynthesis or two types. Light Reflected light Absorbed light Transmitted light Chloroplast 1.3 Mechanism of Photosynthesis
    6. 6. Types of reactions Light Reaction (Hill reaction) Dark Reaction The reactions of photosynthesis that occur in the presence of light is called light reaction During this phase the energy required for Carbon fixation is generated. The reactions of photosynthesis that occur in the absence of light is called dark reaction .
    7. 7. • To understand photosynthesis let us know the reactions that occur in the presence of light. i:e Oxidation and reduction process Oxidation: 1. Addition of oxygen atom 2. removal of hydrogen atom 3. removal of electrons from atom Reduction: 1. Removal of oxygen atom 2. Addition of hydrogen atom 3. Addition of electrons from atom 1.Light Reactions
    8. 8. • When a substance is oxidised the hydrogen and electrons removed from this substances are transformed to another substance. • The substance which accepts hydrogen and electrons get reduced. • The substances which gives electrons are called DONAR and accepts electrons are called ACCEPTOR. • DH2 + A D + AH2 Reduced Donar Oxidized acceptor Oxidized Donar Reduced Acceptor
    9. 9. • These acceptors which accept electrons are called ELECTRON ACCEPTORS. • Eg: Ferridoxins Adenine dinucleotide ( NAD) Nicotinamide adenine dinucleotide phosphate ( NADP) Plastoquinones Cytochromes (Fan in Personal computer) When an electron acceptor is reduced it may transfer the Hydrogen and electrons to another acceptor molecule
    10. 10. Mechanism of photosynthesis 1.During Ps Chlorophyll molecule traps solar energy and gets oxidized • When light falls on the chlorophyll, energy present in the photons is absorbed by the chlorophyll molecule. • This energy pushes an electron in the chlorophyll molecule to a higher energy level. • This electron from chlorophyll is transferred to an electron acceptor as a result chlorophyll gets oxidized by loosing an electron and the acceptor gets reduced by accepting the electron from chlorophyll. • Thus the energy present in the photon of the sun light is used to eject an electron from chlorophyll. This is the basic mechanism by which solar energy is trapped by chlorophyll. • Chlorophyll Chlorophyll* chlorophyll + ẽ • A + ẽ A-- + ve (Low energy state ) (High energy state) (Oxidized) ( Electron) (Acceptor oxidized) (electron) (Acceptor reduced
    11. 11. 2.Chlorophyll splits water molecule and gets back its electron from water • With the removal of electron, chlorophyll is in oxidation state. • This oxidising power of chlorophyll is used for splitting of water molecule to liberate electrons. • By accepting these electrons, chlorophyll returns to its original state. • Oxygen is formed when the chlorophyll splits water molecule. • This oxygen escapes in to atmosphere. • 2 H2O 4 H+ + 4 ẽ - + O2 • 4 ẽ - + 4 chl 4 chl • 2 H2O + 4 Chl 4 Chl + 4H+ O2 • In this reaction water molecule is split by light activated chlorophyll . Hence this process is called PHOTOLYSIS of water • Light does not split water molecule directly it acts through chlorophyll molecule in PS II (Water) (Protons) (Electrons) (oxygen) (Water) (Chlorophyll oxidised) (Chlorophyll reduced)
    12. 12. 3.ATP AND NADPH are formed during photosynthesis • Protons (derived from splitting of water molecule) are left behind are accumulate in thylokoids. • When their concentrations becomes sufficiently high they are transported across the thylokoid membrane in to stroma. • The energy in the movement of protons is used to produce ATP. • The electrons from PSII are taken up by PS I through a serious of other acceptor molecules in the PS I, these electrons are transferred to NADP to produce NADPH. • Up to this stage all the reactions occur only when light is present. There fore all these reactions are called LIGHT REACTIONS. • Oxygen , ATP and NADPH are the end products of light reactions.
    13. 13. Light NADPH OH- 2 H+ CARBOHYDRATES Co2 ½ O2NADP Formation of carbohydrates and NADPH
    14. 14. 1.3.2 The Dark reaction or Carbon fixation • Co2 Glucose in a series of reactions that occur in stroma(Chloroplast). • ATP & NADPH produced in the light reactions are used in these reactions. • The entire reaction from Co2 to productions of glucose is observed by American scientist Melvin Kelvin. • So it is called “Calvin Cycle. Calvin received Nobel prize fro this work.
    15. 15. Calvin Cycle 6 Co2 ( 1 mol) 6 Ribulose 1, 5 Di phosphate 6 Hexose Sugar 1,5 Diphosphate 2 PGA Glyceraldehyde 3 – Phosphate Glucose Corbon Sugar (6 mol) + 2 Phosphates Attached to it 6 molecules of 6 carbon sugar phosphate Is formed 6 HS 1,5 D is highly unstable compound and it Breaks down in to 2 Phosphoglyceric Acid (Each PGA has 3 Carbon atoms) ATP & NADPH are produced in Light reaction Are used up at this stage (3 Carbon atoms) 2 mol of G 3 P (2 x 3=6 C atoms are used to produce 1 mol Glucose ( 6 c atoms) (Glucose is converted to Starch) 10 mol of G 3 P (10 x 3 = 30 C ) are used to regenerate 6 mol of R 1, 5 D ( 6 x 5 = 30 C atoms)
    16. 16. 2 H+ + OH - 1 /2 Water-splitting photosystem Reaction- center chlorophyll Light Primary electron acceptor Energy to make Electron transport chain Primary electron acceptor Primary electron acceptor NADPH-producing photosystem Light NADP+ 1 2 3 How the Light Reactions Generate ATP and NADPH
    17. 17. • The production of ATP by chemiosmosis in photosynthesis Thylakoid compartment (high H+ ) Thylakoid membrane Stroma (low H+ ) Light Antenna molecules Light ELECTRON TRANSPORT CHAIN PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE
    18. 18. • The Calvin cycle makes sugar from carbon dioxide – ATP generated by the light reactions provides the energy for sugar synthesis – The NADPH produced by the light reactions provides the electrons for the reduction of carbon dioxide to glucose Light Chloroplast Light reactions Calvin cycle NADP+ ADP + P • The light reactions convert solar energy to chemical energy – Produce ATP & NADPH AN OVERVIEW OF PHOTOSYNTHESIS
    19. 19. PHOTOSYNTHESIS • Sunlight provides ENERGY CO2 + H2O produces Glucose + Oxygen 6CO2 + 6H2O C6H12O6 + 6O2
    20. 20. Steps of Photosynthesis • Light hits reaction centers of chlorophyll, found in chloroplasts • Chlorophyll vibrates and causes water to break apart. • Oxygen is released into air • Hydrogen remains in chloroplast attached to NADPH • “THE LIGHT REACTION”
    21. 21. Steps of Photosynthesis • The DARK Reactions= Calvin Cycle • CO2 from atmosphere is joined to H from water molecules (NADPH) to form glucose • Glucose can be converted into other molecules with yummy flavors!
    22. 22. • In most plants, photosynthesis occurs primarily in the leaves, in the chloroplasts • A chloroplast contains: – stroma, a fluid – grana, stacks of thylakoids • The thylakoids contain chlorophyll – Chlorophyll is the green pigment that captures light for photosynthesis Photosynthesis occurs in chloroplasts
    23. 23. • The location and structure of chloroplasts LEAF CROSS SECTION MESOPHYLL CELL LEAF Chloroplast Mesophyll CHLOROPLAST Intermembrane space Outer membrane Inner membrane Thylakoid compartmentThylakoidStroma Granum StromaGrana
    24. 24. • Chloroplasts contain several pigments Chloroplast Pigments – Chlorophyll a – Chlorophyll b – Carotenoids – Xanthophyll Figure 7.7
    25. 25. Chlorophyll a & b •Chl a has a methyl group •Chl b has a carbonyl group Porphyrin ring delocalized e- Phytol tail
    26. 26. Different pigments absorb light differently
    27. 27. Cyclic Photophosphorylation • Process for ATP generation associated with some Photosynthetic Bacteria • Reaction Center => 700 nm
    28. 28. Photon Photon Water-splitting photosystem NADPH-producing photosystem ATP mill • Two types of photosystems cooperate in the light reactions
    29. 29. Primary electron acceptor Primary electron acceptor Electron transport chain Electron transport Photons PHOTOSYSTEM I PHOTOSYSTEM II Energy for synthesis of by chemiosmosis Noncyclic Photophosphorylation • Photosystem II regains electrons by splitting water, leaving O2 gas as a by-product
    30. 30. • The O2 liberated by photosynthesis is made from the oxygen in water (H+ and e- ) Plants produce OPlants produce O22 gas by splitting Hgas by splitting H22OO
    31. 31. • Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons • The excited electrons are passed from the primary electron acceptor to electron transport chains – Their energy ends up in ATP and NADPH In the light reactions, electron transportIn the light reactions, electron transport chains generate ATP, NADPH, & Ochains generate ATP, NADPH, & O22
    32. 32. • The electron transport chains are arranged with the photosystems in the thylakoid membranes and pump H+ through that membrane – The flow of H+ back through the membrane is harnessed by ATP synthase to make ATP – In the stroma, the H+ ions combine with NADP+ to form NADPH Chemiosmosis powers ATP synthesis in the light reactions
    33. 33. Summary—Light Dependent Reactions a. Overall input light energy, H2 O. b. Overall output ATP, NADPH, O2 .
    34. 34. • Animation is of the Calvin Cycle Note what happens to the carbon dioxide and what the end product is. • Second animation of the Calvin Cycle is very clear and even does the molecular bookkeeping for you.
    35. 35. Light Independent Reactions aka Calvin Cycle Carbon from CO2 is converted to glucose (ATP and NADPH drive the reduction of CO2 to C6H12O6.)
    36. 36. Light Independent Reactions aka Calvin Cycle CO2 is added to the 5-C sugar RuBP by the enzyme rubisco. This unstable 6-C compound splits to two molecules of PGA or 3-phosphoglyceric acid. PGA is converted to Glyceraldehyde 3-phosphate (G3P), two of which bond to form glucose. G3P is the 3-C sugar formed by three turns of the cycle.
    37. 37. Summary—Light Independent Reactions a. Overall input CO2 , ATP, NADPH. b. Overall output glucose.
    38. 38. Review: Photosynthesis uses light energy to make food molecules Light Chloroplast Photosystem II Electron transport chains Photosystem I CALVIN CYCLE Stroma Electrons LIGHT REACTIONS CALVIN CYCLE Cellular respiration Cellulose Starch Other organic compounds • A summary of the chemical processes of photosynthesis
    39. 39. Types of Photosynthesis C3 C4 CAM Rubisco: the world’s busiest enzyme!
    40. 40. Competing Reactions • Rubisco grabs CO2, “fixing” it into a carbohydrate in the light independent reactions. • O2 can also react with rubisco, inhibiting its active site – not good for glucose output – wastes time and energy (occupies Rubisco)
    41. 41. Photorespiration • When Rubisco reacts with O2 instead of CO2 • Occurs under the following conditions: – Intense Light (high O2 concentrations) – High heat • Photorespiration is estimated to reduce photosynthetic efficiency by 25%
    42. 42. Why high heat? • When it is hot, plants close their stomata to conserve water • They continue to do photosynthesis  use up CO2 and produce O2  creates high O2 concentrations inside the plant  photorespiration occurs
    43. 43. C4 Photosynthesis • Certain plants have developed ways to limit the amount of photorespiration – C4 Pathway* – CAM Pathway* * Both convert CO2 into a 4 carbon intermediate  C4 Photosynthesis
    44. 44. Leaf Anatomy • In C3 plants (those that do C3 photosynthesis), all processes occur in the mesophyll cells. Image taken without permission from http://bcs.whfreeman.com/thelifewire| Mesophyll cells Bundle sheath cells
    45. 45. C4 Pathway • In C4 plants photosynthesis occurs in both the mesophyll and the bundle sheath cells. Image taken without permission from
    46. 46. C4 Pathway • CO2 is fixed into a 4- carbon intermediate • Has an extra enzyme– PEP Carboxylase that initially traps CO2 instead of Rubisco– makes a 4 carbon intermediate
    47. 47. C4 Pathway • The 4 carbon intermediate is “smuggled” into the bundle sheath cell • The bundle sheath cell is not very permeable to CO2 • CO2 is released from the 4C malate  goes through the Calvin Cycle C3 Pathway
    48. 48. How does the C4 Pathway limit photorespiration? • Bundle sheath cells are far from the surface– less O2 access • PEP Carboxylase doesn’t have an affinity for O2  allows plant to collect a lot of CO2 and concentrate it in the bundle sheath cells (where Rubisco is)
    49. 49. CAM Pathway • Fix CO2 at night and store as a 4 carbon molecule • Keep stomates closed during day to prevent water loss • Same general process as C4 Pathway
    50. 50. How does the CAM Pathway limit photorespiration? • Collects CO2 at night so that it can be more concentrated during the day • Plant can still do the calvin cycle during the day without losing water
    51. 51. Summary of C4 Photosynthesis • C4 Pathway – Separates by space (different locations) • CAM Pathway – Separates reactions by time (night versus day)

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