PHOTOSYNTHESIS in plants and others.ppt

photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds.

1. I. Introduction to photosynthesis
•From the Greek
PHOTO = produced by light
SYNTHESIS = a whole made of parts put
together.
Definition:PHOTOSYNTHESIS istheprocess
wherebyplants,algae,somebacteria,
usetheenergyofthesuntosynthesizeorganic
compounds(sugars)frominorganiccompounds
(CO
2andwater).

2. WHY IS PHOTOSYNTHESIS
SO IMPORTANT?
PHOTOSYNTHESIS isoneofthemost
importantbiologicalprocessonearth!
•Provides the oxygen we breathe
•Consumes much of the CO
2
•Food
•Energy
•Fibers and materials

3. GENERAL FORMULA FOR
PHOTOSYNTHESIS
light
6 CO
2+ 6 H
2O---------> C
6H
12O
6+ 6 O
2
pigments, enzymes
* *
•Oxygenonearthallowedfortheevolutionofaerobic
respirationandhigherlife-forms.
•Respiration: extracting energy from compounds (sugars)
C
6H
12O
6+ O
26 CO
2+ ATP

4. II.PROPERTIES OF LIGHT
Virtually all life depends on it!
•Lightmovesinwaves,inenergyunits
calledPHOTONS
•EnergyofaPHOTONinverselyproportional
to its wavelength
•Visiblelight(betweenUVandIR)occursin
a spectrum of colors

5. Visible light contains just the right amount of
energy for biological reactions

6. Light is absorbed by pigments
•The primary pigment for photosynthesis is
chlorophyll a
•It absorbs blue-voilet and redlight, not green
(green light is reflected back!)
Absorption spectrum
of chlorophyll a

7. •Absorption spectrumof chlorophyll a:
BLUE & RED
•Action spectrumof photosynthesis closely
matches absorption spectrum of
chlorophyll a, but not perfectly (due to
accessory pigments)

8. Accessorypigmentslikechlorophyllband
carotenoids(beta-carotene,lycopene):
•absorblightatdifferentwavelengths,(extendingthe
absorptionrangeblueandgreenregion).
•helptransfersomeenergytochlorophylla
•protectcellfromharmfulbyproducts

9. Chlorophyllaistheprimary
photosyntheticpigmentthatdrives
photosynthesis.
Accessorypigmentsabsorbat
differentwavelengths,extending
therangeoflightusefulfor
photosynthesis.

10. Where does photosynthesis occur?

11. The plant cell

12. III. Chloroplast structure and
function: solar chemical factory

13. Chloroplast structure
•Football shaped
•Double membrane
•Stroma
•Thylakoid
membrane
•Grana (stacks)
•Lumen
(inside thylakoid)
stroma
Grana
thylakoids
lumen

14. Inside a Chloroplast
•Remember: Structure correlates to function!

15. Overview of photosynthesis:
Note: The Light and “Dark”or Carbon
reactions happen at different sites in the
chloroplast
LIGHT
REACTIONS
(Thylakoids)
“DARK” or CARBON
REACTIONS
(Stroma)
light
ATP
NADPH
(ENERGY)
H2O
O2
(OXYGEN GAS)
CO2
C6H12O6
(GLUCOSE)

16. IV. The Light Reactions
1. Light dependent
2. Occur in the thylakoid membraneof chloroplast
4.Use light energy(photons) to generate two
chemical energycompounds: ATP & NADPH
5.Two types; NON-Cyclic (Z-scheme) and cyclic
photophosphorylation.
3. Wateris split into oxygen gas(O
2) and H
+

17. Chemical energy compounds
made in the light reactions
ADP + Pi + Energy ATP
adenosine inorganic adenosine
diphosphate phosphate triphosphate
NADP
+
+ 2e-+ H
+
NADPH
Nicotinamide adenin dinucleotide phosphate

18. Cyclic photophosphorylation
(Z-scheme)
(Manganese complex)

20. Cyclic photophosphorylation

21. Summary of the Light reactions
2 H
2O + 2 NADP
+
+ 3 ADP + 3 P
i
O
2+ 2 NADPH + 3 ATP + 4 e
-
+ 2 H
+
(gas)
Light reactions: Chemical energy compounds
are made from light energy, water is split into
O
2and protons

22. V. The“Dark” or Carbon Reactions
1. Light independent (can occur in light or dark;
some enzymes require activation by light)
2. Occur in the stromaof chloroplasts
3. Use the chemical energyproduced in Light
Reactions (ATP; NADPH) to reduce CO
2to
carbohydrate (sugar).
4.CO
2is converted to sugar by entering the
Calvin Cycle

23. CO
2
RuBP
Ribulose bisphosphate
rubisco
3-PGA
3-phosphoglycerate
ATP
ADP
NADPH
NADP
+
Pi
ATP
ADP
carboxylation
reduction
regeneration
GAP
Glyceraldehyde 3-phos.
sugars
The Calvin Cycle
•Named for M. Calvin
•3 phases, 13 steps
•CO
2goes 6 cycles
to produce 1 glucose
Phosphoglycerate
kinase

26. The Calvin Cycle
•CO
2enters the Calvin Cycle
•Firstproductisa3-carbonmolecule:3-PGA
(phosphoglycericacid).That’swhyit’salso
calledC-3cycle.
•EnzymeRUBISCO(ribulosebisphosphate
carboxylase/oxygenase)isthemainenzymethat
catalyzesthefirstreactionsoftheCalvinCycle.
•RUBISCO: Is the most abundant protein on
earth!

27. Most plants use the Calvin Cycle to
Convert CO
2into sugars.
These plants are called C-3 plants

28. Summary of Carbon Reactions
6 CO
2+ 18 ATP + 12 NADPH + 12 H
2O
C
6H
12O
6+ 18 ADP + 18 P
i+ 12 NADP
+
+ 6 H
2O + 6 O
2
glucose
Carbon reactions: Use CO
2and chemical energy (ATP &
NADPH) to produce sugars by means of the Calvin Cycle

29. Limitations on Photosynthesis
•Photosynthesis is not perfect in C-3 plants,
it is only 1 -4 % efficient
•Low efficiency due to photorespiration
•Photorespirationoccurs when internal CO
2
concentration becomes too low(drought);
rubisco begins fixing oxygen.

30. C-4 plants are more efficient
•C-4 plants first product is a 4-carbon molecule
•The C-4 plants (sugar cane, corn, etc.), are more
efficient than C-3 plants –they grow in
hotter climates with more light.
•For example, sugar cane’s
photosynthetic efficiency is
7%
•C-4 plants have a different
leaf anatomy

31. C-3 vs. C-4 leaf anatomy
Net venation Parallel venation

32. VI. Summary of Photosynthesis:
1.Light energy absorbed by chlorophyll a
drives the reactions of photosynthesis.
2. Converts light energy into chemical
energy to make organic compounds.
3. CO
2and H
2O used to produce
C
6H
12O
6(glucose) and O
2(gas).

33. 4.LightReactionsoccurinthylakoidsofthe
chloroplasts;ATPandNADPHareformed;
waterissplittoO
2(gas)andprotons.
5.CarbonReactionsoccurinstroma–Calvin
CyclefixesCO
2toproduceC
6H
12O
6
(glucose).
6.Lowefficiency,about1-4%inC-3plants.
7.Nevertheless,PHOTOSYNTHESISisstillthe
mostimportantbiologicalprocessonearth!

34. Importance of photosynthesis and the
impact that it has in all our lives.
Without photosynthesis, virtually all
plants and animals would become
extinct.

35. RESPIRATION
•Process of making energy of food available in
the cell…
•Involves breaking down
•Complicated molecules into simple molecules
(C
6H
12O
6, sugars) (CO
2, water)

36. RESPIRATION
The energy held by complicated molecules is held
temporarily as ATP (energy currency)
C
6H
12O
6+ 6 O
26CO
2 + 6 H
2O + 36 ATP
(glucose) (energy)
Respiration occurs mainly in
Mitochondria and Cytoplasm

37. Stages of Respiration
Cellular Respiration has three main stages:
•Glycolysis
•Krebs Cycle
•Electron transport system

38. 3 Stages of cellular respiration
•Glycolysis: Splitting of glucose –2 net ATP generated
•Krebs Cycle: Energy of glucose molecule is harvested
as ATP (2) –it occurs in the mitochondria (matrix)
•Electron Transport System: also happens in the
mitochondria, more ATP are generated (32).
•For each glucose molecule, total ATP = 36
•Only 39% efficient, rest is lost as heat.

39. Photosynthesis Respiration
•Reaction:CO2+H2O+sunC6H12O6+O2+H2O C6H12O6+O2CO2+H2O+36ATP
•Reactants:Carbon dioxide, water, sun Glucose, oxygen
•Products:Glucose Energy
•By-products:Oxygen Carbon dioxide, water
•Cellular location:Chloroplasts Cytoplasm, mitochondria
•Energetics:Requires energy Releases energy
•Chemical paths:Light reactions & Glycolysis, Krebs cycle
Calvin cycle & Electron Transport Syst.
•Summary:Sugar synthesized using Energy released from
energy from the sun sugar breakdown

40. Photosynthesis and respiration
•Photosynthesis and respiration are
complimentary reactions…

41. PHOTOSYNTHESIS RESPIRATION
CO
2+ H
2O O
2 + SUGARS SUGARS + O
2 H
2O + CO
2
PLANTS,
ALGAE,
BACTERIA
MOST LIVING
ORGANISMS
H
2O H
2O
O
2
O
2CO
2
CO
2
SUGARS
Sunlight
energy
USEFUL CHEMICAL
ENERGY (ATP)

42. The Carbon Cycle
•Carbon from the atmosphere (CO
2) enters the
biosphere by way of plants!
–CO
2used in photosynthesis
–Carbon moves into food chain
•Carbon is released to the physical environment by
respiration
–Release CO
2during respiration
–Amount CO
2fixed in photosynthesis = the amount
released by respiration

43. Carbon Cycle
•Carbon moves from atmosphere to plants to
animals and back to atmosphere.

44. “Look deep into nature,
and then you will
understand everything
better.”
Albert Einstein