PHOTOSYNTHESIS

1. photosynthesis

2. Essential Questions
• What if the sun quit shining?
• Is the process of photosynthesis dependent
on light?
• What is photosynthesis?
• What organisms undergo photosynthesis?
• How do plants make food?
• What adaptations does a leaf have to
undergo photosynthesis?
• What are the raw materials needed for
photosynthesis?

3. Essential Questions
• What are the inputs and outputs of
photosynthesis.
• How do the light dependent reactions
occur?
• How do the light independent reactions
occur?
• What is the Calvin Cycle?
• What factors affect photosynthesis?
• Why is photosynthesis important to the
environment?

4. Important Vocabulary
• chlorophyll
• Accessory pigment
• Stomata
• Guard cell
• Spongy layer
• Palisade layer
• Epidermis
• CHLOROPLAST
– GRANUM
– THYLAKOID
– STROMA
• NADP & NADPH
• Photosystem II and I
• ATP synthase
• Carbon Fixation
• Rubp
• Rubisco
• G3P
• ATP & ADP

5. The Photosynthesis Song!

6. Photosynthesis

7. The Nature of Light
• Visible light is the component
of the Electromagnetic
spectrum of energy that a
plant uses for photosynthesis.
• Photon – particle of light!

9. What Colors do we see?
• Why do leaves of plants look green?
– Leaf pigments….like chlorophyll.
• Pigments can absorb, reflect, or transmit the
light energy.
• An object that absorbs all colors is BLACK.
• An object appears that color when it reflects
that color----- GREEN PLANTS!

11. Photosynthetic pigments
Found in the Chloroplast.
• Chlorophyll a – absorbs less blue and more
red light. It is directly involved in
photosynthesis.
• Chlorophyll b – absorbs more blue and less
red light. It is an accessory pigment – assists
chlorophyll a.
Other accessory pigments:
• Carotenoids – absorb blue light. Reflect
yellow, red, orange light.

12. What does the graph below represent?

13. LEAF Structure

14. Leaves and
Photosynthesis

15. Adaptations for Nutrition – The Leaf
• Cuticle – waxy
outermost
layer
• Epidermis – 1
cell thick.
Allows light to
penetrate.
• Stomate – on
lower
epidermis. Gas
exchange.
Water
transpiration.
• Guard Cell –
regulates
Mesophyll – contains vascular bundle AND…
+ Palisade layer – site of photosynthesis.
+ Spongy layer – irregular cells, large air
spaces…for diffusion of gases.

16. Chloroplasts

17. THE CHLOROPLAST

18. Chloroplast
• Thylakoid –
– photosynthetic membranes.
– Arranged in stacks called GRANA.
– Contain chlorophyll: photosystems
– Light DEPENDENT reactions occur
• Stroma –
– Outside the thylakoid
– Light INDEPENDENT reactions occur.

19. Photosynthesis – an overview
(the absolute minimum you must know!!!
• 6CO2 + 6H2O light
C6H12O6 + 6O2
• Light energy needed - Capture LIGHT - PHOTO
• ATP used and generated
• NADP+
:the electron carrier, that combines with 2 electrons
and one hydrogen ion.
• NADP+
becomes reduced into NADPH, when it receives the
electrons.
• Glucose (SYNTHESIS) and oxygen are made.
NADP : nicotinamide adenine dinucleotide phosphate

20. Photosynthesis – an overview

21. The
Light
Reactions

22. Light Reactions

23. Organization of a
Thylakoid

24. Light Reaction(overview)
Produce
OXYGEN gas
and convert
ADP and
NADP+ into
energy
carriers ATP
and NADPH.

25. PHOTOSYSTEM II (PII)
• Chlorophyll pigments (purple circles) in thylakoid membrane absorb light
energy.
– The energy is absorbed by electrons…passed to ETC.
PHOTOLYSIS
• During this process, H2O is broken down, and O2 is released.
• Electrons from hydrogen replace electrons in chlorophyll.
• H+ begin to create a positive gradient in the THYLAKOID.

26. • Electrons lose energy as they pass down the ETC.
• Energy lost “pumps” more H+ into the Thylakoid thru membrane
by active transport.
PHOTOSYSTEM I
• Light energy re-energizes electrons
• Electrons combine with NADP and H+ to form NADPH – an
electron carrier
• NADPH moves into the stroma for Light Independent Rxns.

27. Production of ATP
• The concentration of H+
ions inside the thylakoid membrane
becomes much higher than the concentration outside.
• H+
ions rush out through membrane protein called ATP
synthase.
• The ATP synthase spins like a turbine and the energy is
used to bind ADP and P together to form ATP.

28. Summary of the Light
Reactions
• Input:
• Light
• Water
• ADP
• NADP+
Output:
• 18 ATP
• 12 NADPH
• Oxygen
What do you need for more light
reactions to occur?

29. Summary of the Light
Reactions
• Input:
• Light
• Water
• ADP
• NADP+
Output:
• 18 ATP
• 12 NADPH
• Oxygen
ADP, and NADP+

30. Summary of the Light
Reactions
• Input:
• Light
• Water
• ADP
• NADP+
Output:
• 18 ATP
• 12 NADPH
• Oxygen
What is the waste product of
photosynthesis?

31. Summary of the Light
Reactions
• Input:
• Light
• Water
• ADP
• NADP+
Output:
• 18 ATP
• 12 NADPH
• Oxygen
Oxygen

33. Light Independent Reactions

34. Light Independent Reactions
(overview)
aka – Carbon Fixation, Calvin Cycle, Dark Rxns.
• Uses CO2 to form a 2- 3 carbon molecules
• Needs ATP
• Needs NADPH – is oxidized
• Carbon Molecule reduced
• Leaves 6 – 5 carbon molecules

36. Light Independent Reactions

37. Light Independent reactions
Carbon Fixation
• 6CO2 enter the cycle and bonds
with 6 – 5 carbon molecules
(Rubp)
– Catalyzed by enzyme Rubisco.
• These molecules split into 12 – 3
carbon molecules.

38. Light Independent reactions
Reduction:
• Each 3 carbon molecule is REDUCED
by 12 NADPH (oxidized).
• 12 ATP IS NEEDED!
• Result: G3P the 3 – carbon molecule
that will become glucose.
– 2 – G3P exit the Calvin Cycle to become
Glucose

39. Light Independent reactions
Regeneration:
• 10 – G3P molecules are rearranged into
5 – 6 carbon molecules (Rubp)
• 6 ATP needed

40. Calvin Cycle Reactions

41. Fate of G3P

42. Calvin Cycle Reactions
• Importance of the Calvin Cycle
– G3P (glyceraldehyde-3-phosphate) can be
converted to many other molecules
• The G3P can form:
– Fatty acids and glycerol to make plant oil
– Glucose phosphate (simple sugar)
– Fructose (which with glucose = sucrose)
– Starch and cellulose
– Amino acids

43. Fate of G3P

44. Photosynthesis and
Respiration Compared

45. How the Rate of
Photosynthesis can be
affected.

46. Rate of Photosynthesis
• What is a rate?
• It is the activity per unit time.
• What factors can affect the photosynthetic rate?
• Light intensity
• Temperature
• Oxygen
• Carbon Dioxide Concentration
• Sometimes these factors are called
LIMITING FACTORS.

47. The Effect of Light Intensity on
Photosynthetic Rate

48. The Effect of Temperature on
Photosynthetic Rate

49. The Effect of Light Intensity and Temperature on
Photosynthetic Rate
Which is
the
limiting
factor
here;
light
intensity
or
temp.?

50. Carbon Dioxide
Concentration

51. Oxygen Concentration
What would a graph for increasing levels of CO2 look like?