1. Biology 20 Unit 3 Chapter 5 Photosynthesis
McGraw - Hill Ryerson pages 169 to 181

2. 6H2O + 6CO2 ----------> C6H12O6+ 6O2
Photosynthesis
A process that converts solar energy into chemical energy
Mean ‘Light” and “to make or build”.
Occurs in all plants, some algae, some bacteria, some protists
light
6H2O + 6CO > C6H12O6+ 6O2

3. Chloroplasts and Photosynthetic Pigments
Light
Part of electromagnetic radiation (EMR)
Can be described by its wave characteristic or as particles of energy called photons.

4. A spectroscope separates individual wavelengths of the Sun
Visible light is only 3 % of the total energy

5. I.) Chlorophyll
Light – absorbing, green colored pigment
Absorbs photons and begins process of photosynthesis
Color of pigment comes from wavelengths of light reflected (in other words, those not absorbed).
What color is absorbed if you see a red shirt? What colors are reflected?

7. Types of Chlorophyll Pigments include:
All photosynthetic organisms have chlorophyll "a" 
Accessory pigments absorb energy that chlorophyll "a" does not absorb
Pigments include:
Chlorophyll "b" (also c, d, and e in algae and protistans)
Xanthophylls
Carotenoids

8. Absorption spectrum of chlorophylls “a” and “b”

9. Spectrophotometer
Instrument that determines wavelengths of light absorbed or reflected by a pigment
Chlorophyll "a" reflects green light waves and absorbs red and blue

10. Leaves during fall season
Onset of cooler autumn temperatures and less sunlight
Plants stop producing chlorophyll molecules
Reveals yellow, red, brown colors of leaves.
leaves
Pumpkin Eyes Games

11. II.) Chloroplasts Found in leaves Structure of the leaf
Primary photosynthetic organs of most plants
Structure of the leaf
Chloroplasts have chlorophyll
Captures light for food production
Xylem and phloem transport water and food
Gases enter and exit from stomata
Waxy cuticle and epidermis protect plant from water loss

12. Xylem Structure Phloem Structure

13. Leaf Anatomy

15. Chloroplast anatomy 1. 2 membranes Outer and inner 2. Stroma
Protein – rich semi liquid material in interior of chloroplast
Between two membranes

17. 3. Thylakoid System of interconnected flattened membrane sacs
Form a separate compartment within stroma of chloroplast
Stack on top of one another, forming grana
1 chloroplast has 60 grana
Each has 30 – 50 thylakoids

18. 4. Lamellae
Groups of unstacked thylakoids
Between grana

20. 5. Thylakoid membrane and lumen
Photosynthetic membrane within chloroplast
Contains:
Light – gathering pigment molecules
Electron transport chains
Lumen: Fluid – filled space inside a thylakoid

22. Chloroplast

23. Chloroplast structure
Structure of thylakoid system greatly  surface area of thylakoid membrane
Thus,  efficiency of photosynthesis
Chloroplasts are able to replicate, through division, independently of cell
Lipid droplets and starch grains are also present in chloroplast
Plant growth

24. Separating Pigments Using Chromatography
Paper chromatography is a method used to separate different compounds in a solution
As solvent moves up paper, it will carry dissolved compounds of solution
Compounds move up paper at different rates due to their solubility in the solvent and their size

25. tip of the filter paper is placed in solvent
as solvent moves up the paper it will carry pigments
size: smaller pigments travel further up paper
solubility: more soluble pigments travel further up paper

26. The Reactions of Photosynthesis
A process made up of a series of complex chemical reactions.
A variety of intermediate and final energy rich molecules are formed.
Occurs in the thylakoid membrane and stroma of the chloroplast.
light
6H2O + 6CO > C6H12O6+ 6O2
Photosynthesis

27. Energy Containing Molecules Formed During Photosynthesis
Function
ATP (adenosine triphosphate)
Principal energy – supply molecule for cellular functions of all cells
Provides an immediate source of energy for cellular processes
Formed by addition of ADP and Pi (phosphate)

28. ATP ADP + Pi Energy is stored when ATP is formed
Energy is released, when needed, by reversal of reaction
ATP
Energy input
Energy output
ADP + Pi

29. Energy Containing Molecules Formed During Photosynthesis
Function
NADPH (nicotinamide dinucleotide phosphate)
At several places during photosynthesis, NADP+ accepts 1 H atom and 2 e- to form NADPH
NADPH is an electron donor, thus becomes NADP+ again
Involved in energy transfers

30. Energy Containing Molecules Formed During Photosynthesis
Function
glucose
Transport molecule (“blood sugar”)
Medium – term energy storage in most cells

31. Oxidation – Reduction Reactions
A reaction in which an atom or molecule loses electrons
Reduction
A reaction in which an atom or molecule gains electrons
Electron transfers between 2 substances always involve both oxidation / reduction reactions
“LEO” the lion says “GER”

33. Oxidation / reduction examples
i.) ATP
Reduction of ADP
ADP (accepts electrons) + Pi  ATP
Storage of energy
Oxidation of ATP (energy)
ATP (releases elections)  ADP + Pi
Release of energy
ADP and Pi can be reused in future reduction reactions

34. Oxidation / reduction examples
ii.) NADPH
Reduction of NADP+
NADP+ + H  NADPH
NADPH is now stable and can release energy to the next electron acceptor
Oxidation of NADPH
NADPH  NADP+ + H
NADP+ can be reused in future reduction reactions

35. I.) An Overview of Photosynthesis
3 stages
1. Capture solar E and transfer it to e-
2. Use captured solar energy to make ATP; transfer high energy e- to NADP+; NADPH is then used as a high energy e- carrier
3. Use energy stored in ATP and NADPH to form energy – rich molecules such as glucose, from CO2

36. 6H2O + 6CO2 ----------> C6H12O6+ 6O2
Photosynthesis
*Reworked equation:
12 H2O + 6 CO2 + solar E → C6H12O6 + 6 O2 + 6 H2O
light
6H2O + 6CO > C6H12O6+ 6O2

37. * Reactants of photosynthesis are the products of cellular respiration.

38. Light Dependant (Stages 1 and 2)
A.k.a. noncyclic photophosphorylation or noncyclic electron flow
I.e., linear and ADP + Pi
Require chlorophyll
Occur in thylakoid membranes of chloroplast

39. Light Independent (Stage 3)
occur during day or night
AKA: Calvin cycle
Carbon fixation occurs
Incorporation of CO2 (g) into organic compounds such as glucose
Occur in stroma of chloroplast
Use ATP and NADPH from light dependent reactions
Enzymes are required

40. . W

41. Stage 1: Capturing Solar Energy
Photosystems- in thylakoid membranes
Cluster of chlorophyll and other pigments packed into thylakoid membranes.
Photosystem I uses chlorophyll "a", in the form referred to as P700
Photosystem II uses a form of chlorophyll "a" known as P680
Operate so that a wide range of wavelengths can be used for photosynthesis. Why?

43. Action of a photosystem

44. Stage 1: Capturing Solar Energy
All pigments within a photosystem capture and absorb photons.
Only 1 pair of chlorophyll molecules/photosystem actually use solar Energy
Found at core of reaction center of photosystem
Antenna pigments
Other pigment molecules
Gather light and transfer it to chlorophyll molecules

45. Stage 1: Capturing Solar Energy
Solar E is captured when a low energy e- in a chlorophyll molecule, from photosystem II, absorbs a photon. Energy is channeled to chlorophyll a.
After a photon of light strikes, chlorophyll a molecules absorb solar E. Donates the electron to the primary electron acceptor in the thylakoid membrane.
Because chlorophyll a donates an electron, it must get another one from somewhere… the splitting of water!

48. Stage 1: Capturing Solar Energy
Two energized e-, from chlorophyll, are removed from photosystem II
e- enters an electron transport chain
e- is passed from one molecular complex to another (like a hot potato)
ATP is made because of the energy release through the chain.
Series of oxidation / reduction reactions

49. Stage 1b- Photolysis Photolysis Occurs in thylakoid lumen
Solar E absorbed by chlorophyll is used to split water into H+, e-, O2 (g)
e- replaces 2e- lost by chlorophyll molecules in photosystem II
O2 (g) exists plant through stomata in leaves or is used to make H2O
H+ will be used later, to help reduce ADP

50. Stage 1: Capturing Solar Energy
2 H2O (l) + energy  4 H+ + 4 e- + O2 (g)

51. Stage 2: Electron Transfer and ATP Synthesis
Purpose:
Form energy – rich molecules
Make ATP from ADP and Pi
2 processes:
Build up of H+ ions
Transfer of electrons

52. a) Electron Transport Chain
Analogy: set of stairs
Solar E excites 2 e- that have been removed from H2O
This “boost” gives e- high potential energy
Potential E is gradually released as e- travel down the stairs
Some of this released E is used to make ATP
e- eventually join H+ ions in the formation of new compounds

53. ATP 2e- 2e- ETC analogy: 2 H+ + 2e- + ½ O2 (g)  H2O H2O
*Series of oxidation – reduction reactions by electron acceptors and donors at each step
2e-
2 H+ + 2e- + ½ O2 (g)  H2O
H2O

54. Electron transport chainD B
Photolysis E
lumen

55. Stage 2: Electron Transfer and ATP Synthesis Events
(A) e-, excited by light at photosystem II, are passed along an ETC.
e- release energy at each step.
(B) Energy from e- is used to pull H+ ions across membrane into lumen
e- have lost most of their energy
H+ ion concentration increases inside lumen and a positive charge builds up

56. (C) e- are transferred from ETC to photosystem I
e- are energized by light
(D) e- are transferred to NADP+
Each NADP+ accepts 2 e- and 1 H+
Thus, NADP+ is reduced to NADPH

59. b.) Chemiosmosis
Due to the build up of H+ in the lumen, concentration of positive ions increases
Electrical gradient results
(E) H+ ions rush through ATP synthase complex
In doing so, H+ ions release energy
Help combine ADP + Pi  ATP
Note: energy stored in H+ ion gradient is derived from energy of e- by photosystem II
Thus, energy used by plant to make ATP comes from the sun!

60. Electron transport chainD B
Photolysis E
lumen

62. Stage 1 and 2 Summary
1. Purpose = convert light energy to ATP and NADPH. 2. ATP and NADPH run the synthesis reactions. 3. ATP synthase channel is used to generate ATP flow of H+ through synthase. 4. No sugar is produced. 5. Oxygen is produced as a waste product and released to the atmosphere (from splitting of water to produce electrons).

63. Links Photophosphorylation

64. Cyclic Electron Flow or Cyclic Photophosphorylation
If a chloroplast runs low on ATP but accumulates NADPH, e- may take an alternative path
Uses photosystem I but not photosystem II
e- cycle back to P700 chlorophyll molecule via the same ETC that functions in noncyclic e- flow
ATP is produced
NADPH nor O2 (g) is produced

66. Cyclic Electron Flow (photophosphorylation)
and Photosystem I

67. Links Cyclic and Noncyclic Photophosphorylation

68. Stage 3: The Calvin Cycle and Carbon Fixation
Occurs in stroma of chloroplast
Includes a large number of light – independent reactions
CO2 enters plants through stomata of leaves
Upon entering Calvin cycle, CO2 is reduced
Utilizes both ATP and NADPH, which were produced from stage 1 & 2
Direct product of Calvin cycle is a 3 carbon sugar, G3P.
Used to create glucose, C6H12O6

70. Stage 3: The Calvin Cycle and Carbon Fixation
C and O atoms are supplied by CO2
H atoms are supplied by photolysis of H2O, from stage 1
3 ATPs and 2 NADPHs are consumed per CO2 that enters the calvin cycle
Thus, the building of one glucose molecule requires 18 ATPs and 12 NADPHs

72. Stage 3: The Calvin Cycle and Carbon Fixation Events
3 steps:
CO2 fixation and reduction.
PGAL molecules produced.
Regeneration of RUBP
Each stage requires enzymes for cycle to occur

73. Step 1: CO2 fixation and reduction
RUBP (ribulose biphosphate), a 5 – C molecule, attaches to CO2
Enzyme for this reaction is RUBP carboxylase
RUBP + CO2  unstable 6 – C molecule
6 – C molecule breaks down into two 3 – C molecules (PGA).
Each 3 PGA molecule becomes reduced
ATP and NADPH supply the energy for this stage

74. Step 2: PGAL production
Each PGA molecule accepts energy from ATP and NADPH.
The 3-C PGA is reduced to form PGAL and water.
PGAL is stable, combines with another PGAL to form glucose.
PGAL has 3 purposes:
Provides chemical energy for the cell.
Combine to form glucose= stored energy for cell.
Recycle to form RuBP.

75. H2O
From light reactions
From light reactions
Back to thylakoid

76. Step 3: Regeneration of RUBP
Needed so that cycle can continue.
Uses ATP from the light dependant reaction.
5 molecules of PGAL are used to form RuBP; only 1 carbon is available to form glucose.
How many turns of the cycle must occur to get 1 glucose? Why?
Glucose is smaller, less reactive and has more energy than ATP and NADPH.

77. Stage 3: The Calvin Cycle and Carbon Fixation Products
Direct product – PGA
Glucose, C6H12O6
NOTE: six revolutions of Calvin cycle are required to make one glucose molecule
6 H2O
ADP, Pi, NADP+, H+

78. Calvin-Benson Cycle

80. Summary
P/S is the process that uses sunlight to convert inorganic compounds into organic compounds.
Photons split water, create ATP and NAPDH. These are used to combine CO2 from air with a 5 Carbon sugar (RuBP).
PGA is produced, is unstable, converts to PGAL. PGAL combines to form RuBP and 1 glucose for every 6 turns.
Ms. Frizz