1. Chapter 8
Photosynthesis

2. 8.1 Objectives: Guiding Question: How do organisms store energy?
1. Describe the role of ATP in cellular activities.
Explain where plants get the energy they need to produce food.
(process of photosynthesis)

3. Chemical Energy and ATP
To maintain homeostasis, all cells must:
Grow
Develop
Move materials around
Build new molecules
Respond to environmental changes
Requires lots of energy to maintain homeostasis
Where does that power come from??

4. Chemical Energy and ATP
Energy – ability to do work
Nearly every activity in society depends on energy
Examples???
Without ability to obtain and use energy, life would cease to exist

5. ATP Living things use chemical fuels
Adenosine Triphosphate – ATP - One of most important compounds that cells use to store and release energy
Adenine
5-carbon sugar (ribose)
3 phosphate groups

6. Storing Energy
Adenosine Diphosphate – ADP – looks like ATP except it has 2 phosphate groups
Cells can store small amounts of it by adding phosphate groups to ADP molecules  produces ATP

7. Releasing Energy
Cells release energy stored in ATP by controlled breaking of chemical bonds b/w 2nd and 3rd phosphate groups
A cell can store energy by adding a phosphate group

8. Using Biochemical Energy
Cells use energy provided by ATP:
Active Transport – sodium-potassium pumps
Pump sodium out and potassium in
ATP provides energy to keep pump working
Maintains carefully regulated balance of ions on both sides of cell membrane
ATP powers movement – energy for motor proteins to contract muscle and power wavelike movement of cilia and flagella

9. Using Biochemical Energy
ATP energy used for:
protein synthesis
Responses to chemical signals at cell surface
Produce light
Blink from firefly

10. Using Biochemical Energy
Most cells have only a small amount of ATP
enough to last only a few seconds of activity
ATP transfers energy well
ATP does not store large amounts of energy well
More efficient for cells to keep only a small supply of ATP on hand
Cells can regenerate ATP from ADP as needed by using energy in foods like glucose

11. Heterotrophs
Cells are not “born” with supply of ATP  must somehow produce it  from chemical compounds we call FOOD
Heterotrophs – organisms that obtain food by consuming other living things
Some eat only plants (herbivore)
Some obtain food from plants indirectly by feeding on plant-eating animals (carnivore)
Both plants and/or animals (omnivore)
Some (mushrooms) obtain food by absorbing nutrients from decomposing organisms in the environment

12. Autotrophs Energy in nearly all food molecules comes from the sun
Autotrophs – organisms that make their own food
Plants, algae, and some bacteria are able to use light energy from the sun to produce food
All life on earth depend on ability of autotrophs to capture the energy of sunlight and store it in the molecules that make up food

13. Photosynthesis
Photosynthesis – process by which autotrophs use energy of sunlight to produce high-energy carbohydrates (sugars and starches)
Photo = light
Synthesis = putting together
chemical energy stored in bonds of carbohydrates

14. Photosynthesis: An Overview
Section 8.2
Photosynthesis: An Overview

15. Objectives:
Guiding Question: What cellular structures and molecules are involved in photosynthesis?
Explain the role of light and pigments in photosynthesis.
Explain the role of electron carrier molecules in photosynthesis.
State the overall equation for photosynthesis

16. How would you….
Design a system to capture the energy of sunlight and convert it into useful form??
Solution = insight to solar power energy source

17. Light Energy from sun travels to Earth in form of light
White light – what our eyes perceive – mixture of different wavelengths
What our eyes can see make up the visible spectrum
Our eyes see different wavelengths as different colors: ROYGBIV

18. Pigments
Pigments – light absorbing molecules plants use to gather the sun’s energy
Chlorophyll – plants’ principal pigment
2 types: Chlorophyll a & Chlorophyll b
Absorb light very well in blue-violet and red regions
Do not absorb light well in green region of spectrum
Plants look green b/c leaves reflect green light

19. Other Pigments
Plants contain red and orange pigments (carotene) that absorb light in other regions of the spectrum
Most of the time, the intense green color of chlorophyll overwhelms the accessory pigments, so we don’t notice them
As temp drops late in year, chlorophyll molecules break down first, leaving reds and oranges

20. Chloroplasts
Chloroplasts – organelle where photosynthesis takes place (plants and other photosynthetic eukaryotes)
Thylakoids – abundance of saclike photosynthetic membranes found in chloroplasts
Pigments (chlorophyll) located in thylakoid membranes
Grana – stacks of interconnected thylakoids
Stroma – fluid portion of chloroplast, outside thylakoids

22. Energy Collection Light is a form of energy
Any compound that absorbs light  absorbs energy
Chlorophyll absorbs visible light
a large fraction of that light energy is transferred directly to electrons in the chlorophyll molecules itself
light energy can produce a steady supply of high-energy electrons, which is what makes photosynthesis work

23. High Energy Electrons
High-energy electrons produced by chlorophyll are highly reactive and require a special “carrier”
High energy electron = hot potato
Must use an oven mitt to transport it
Oven mitt = electron carrier – to transport high-energy electrons from chlorophyll to other molecules
electron carrier - compound that can accept a pair of high-energy electrons and transfer them, along with most of their energy, to another molecule

24. Electron Carrier = NADP+
NADP+ (nicotinamide adenine dinucleotide phosphate) – one type of electron carrier molecule
accepts and holds 2 high-energy electrons, along with a hydrogen ion (H+)
converts NADP+ into NADPH
One way in which some of energy from sunlight can be trapped in chemical form
NADPH carry electrons chemical reactions elsewhere in the cell
Used to help build variety of molecule the cell needs (glucose)

25. Overview of Photosynthesis
Involves many steps
Photosynthesis uses energy of sunlight to convert water and carbon dioxide (reactants) into high-energy sugars and oxygen (products)
Plants use sugars
to produce complex carbs (starches)
to provide energy for synthesis of other compounds (proteins & lipids)

26. Overview of Photosynthesis
Usually produces 6-carbon sugars (C6H12O6) as final product
Reaction in Symbols:
6CO2 + 6H2O (light)  C6H12O6 + 6O2
Reaction in Words:
Carbon dioxide + Water + (light)  Sugars + Oxygen

27. Light-Dependent Reactions
Light-dependent reactions – require direct involvement of light and light-absorbing pigments
Use energy from sunlight to produce energy-rich compounds (ATP)
Occurs in thylakoids (membranes) in chloroplast
Water is source of electrons and hydrogen ions in reactions
Oxygen released as a byproduct

29. Light-independent Reactions
Plants absorb carbon dioxide from atmosphere
Produce carbon-containing sugars (carbohydrates)
ATP and NADPH molecules produced in light dependent reactions
used to produce high-energy sugars from carbon dioxide
No light is required to power the light independent reactions
Occur outside thylakoids (in the stroma)

32. Relationship between reactions diagram

33. The Process of Photosynthesis
Section 8.3
The Process of Photosynthesis

34. Objectives:
Guiding Question: How do photosynthetic organisms convert the sun’s energy into chemical energy?
Describe what happens during light-dependent reactions
Describe what happens during light-independent reactions
Identify factors that affect the rate at which photosynthesis occurs

35. Light-Dependent Reactions
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. The light-dependent reactions take place within the thylakoid membranes of chloroplasts.
Movie? 35

36. Light-Dependent Reactions
Photosynthesis begins when pigments in photosystem II absorb light, increasing their energy level.
Photosystem II
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. The light-dependent reactions take place within the thylakoid membranes of chloroplasts. 36

37. Light-Dependent Reactions
These high-energy electrons are passed on to the electron transport chain.
Photosystem II
Electron carriers
High-energy electron 37

38. Light-Dependent Reactions
Enzymes on the thylakoid membrane break water molecules into:
Photosystem II
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
Electron carriers
High-energy electron
Copyright Pearson Prentice Hall 38

39. Light-Dependent Reactions
hydrogen ions
oxygen atoms
energized electrons
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
Electron carriers
High-energy electron 39

40. Light-Dependent Reactions
The energized electrons from water replace the high-energy electrons that chlorophyll lost to the electron transport chain.
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
High-energy electron 40

41. Light-Dependent Reactions
As plants remove electrons from water, oxygen is left behind and is released into the air.
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. The light-dependent reactions take place within the thylakoid membranes of chloroplasts.
High-energy electron 41

42. Light-Dependent Reactions
The hydrogen ions left behind when water is broken apart are released inside the thylakoid membrane.
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
High-energy electron 42

43. Light-Dependent Reactions
Energy from the electrons is used to transport H+ ions from the stroma into the inner thylakoid space.
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. 43

44. Light-Dependent Reactions
High-energy electrons move through the electron transport chain from photosystem II to photosystem I.
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
Photosystem I 44

45. Light-Dependent Reactions
Pigments in photosystem I use energy from light to re-energize the electrons.
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
Photosystem I 45

46. Light-Dependent Reactions
NADP+ then picks up these high-energy electrons, along with H+ ions, and becomes NADPH.
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH 46

47. Light-Dependent Reactions
As electrons are passed from chlorophyll to NADP+, more H+ ions are pumped across the membrane.
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH 47

48. Light-Dependent Reactions
Soon, the inside of the membrane fills up with positively charged hydrogen ions, which makes the outside of the membrane negatively charged.
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH 48

49. Light-Dependent Reactions
The difference in charges across the membrane provides the energy to make ATP.
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH 49

50. Light-Dependent Reactions
H+ ions cannot cross the membrane directly.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH 50

51. Light-Dependent Reactions
The cell membrane contains a protein called ATP synthase that allows H+ ions to pass through it.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH 51

52. Light-Dependent Reactions
As H+ ions pass through ATP synthase, the protein rotates.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH 52

53. Light-Dependent Reactions
As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
ADP
2 NADP+ 2 2
NADPH 53

54. Light-Dependent Reactions
Because of this system, light-dependent electron transport produces not only high-energy electrons but ATP as well.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
ADP
2 NADP+ 2 2
NADPH 54

55. ATP synthase + O2 2H2O ADP 2 NADP+ 2 NADPH 2
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
ADP
2 NADP+ 2 2
NADPH 55

56. Summary of Light-Dependent Reactions
Produce oxygen gas
Convert ADP and NADP+ into energy carriers ATP and NADPH
These carriers provide energy needed to build high-energy sugars from low-energy carbon dioxide

57. The Calvin Cycle The Calvin Cycle
ATP and NADPH formed by the light-dependent reactions contain an abundance of chemical energy, but they are not stable enough to store that energy for more than a few minutes.
During the Calvin cycle plants use the energy that ATP and NADPH contain to build high-energy compounds that can be stored for a long time. 57

58. The Calvin Cycle
The Calvin cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars.
Because the Calvin cycle does not require light, these reactions are also called the light-independent reactions. 58

59. Six carbon dioxide molecules enter the cycle from the atmosphere and combine with six 5-carbon molecules.
CO2 Enters the Cycle
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.
The Calvin Cycle 59

60. The result is twelve 3-carbon molecules, which are then converted into higher-energy forms.
The Calvin cycle uses ATP and NADPH to produce high-energy sugars. 60

61. The energy for this conversion comes from ATP and high-energy electrons from NADPH.
Energy Input 12
12 ADP 12
NADPH
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.
12 NADP+
The Calvin Cycle 61

62. Two of twelve 3-carbon molecules are removed from the cycle.
Energy Input 12
12 ADP 12
NADPH
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.
12 NADP+ 62

63. The 2 removed molecules are used to produce sugars, lipids, amino acids and other compounds.12
12 ADP 12
NADPH
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.
12 NADP+
6-Carbon sugar produced
Sugars and other compounds 63

64. The 10 remaining 3-carbon molecules are converted back into six 5-carbon molecules, which are used to begin the next cycle. 12
12 ADP
6 ADP 12
NADPH 6
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.
12 NADP+
5-Carbon Molecules Regenerated
Sugars and other compounds 64

65. The Calvin Cycle
The two sets of photosynthetic reactions work together.
The light-dependent reactions trap sunlight energy in chemical form.
The light-independent reactions use that chemical energy to produce stable, high-energy sugars from carbon dioxide and water. 65

66. Mystery Clue
Page 239
Add to your page
I will check on your way out.

67. Factors Affecting Photosynthesis
Temperature, Light, and Water
Among most important factors that affect photosynthesis are temperature, light intensity, and availability of water.
Reactions made possible by enzymes that function best b/w 0oC and 35oC
Above or below these temps could slow down rate of photosynthesis
Low temps, may stop entirely

68. Temperature, Light, and Water
Intensity of light affects rate of photosynthesis
High light intensity increases rate of photosynthesis
After intensity reaches a certain level, plant reaches maximum rate of photosynthesis

69. Temperature, Light, and Water
Water is one of raw materials of photosynthesis
Shortage of water can slow or stop photosynthesis
Water loss can damage plant tissues
Plants that live in dry conditions often have waxy coatings on leaves to redue water loss
May also have biochemical adaptations that make photosynthesis more efficient under dry conditions

70. Photosynthesis Under Extreme Conditions
To conserve water  plants in bright, hot conditions  close small openings in leaves that normally admit carbon dioxide
Keeps plants from drying out
Causes carbon dioxide w/in leaves to fall to very low levels
Photosynthesis slows down or stops

71. C4 Photosynthesis
Specialized chemical pathway that allows them to capture very low levels of carbon dioxide to pass it on to Calvin cycle
1st compound formed in pathway contains 4 carbon atoms
Enables photosynthesis to keep working under intense light and high temperatures
Requires extra energy in form of ATP to function
Examples: corn, sugar cane, sorghum

72. CAM Plants
Carbon dioxide becomes incorporated into organic acids during photosynthesis
Process called Crassulacean Acid Metabolism
Admit air into leaves only at night
In cool darkness, carbon dioxide is combined w/ existing molecules to produce organic acids, “trapping” carbon w/in leaves
During daytime, leaves tightly sealed to prevent loss of water  compounds release carbon dioxide  enable carbohydrate production
Examples: pineapple trees, cacti, “ice plants” (near freeways along west coast to retard brush fires and prevent erosion)

73. Solve the Chapter 8 Mystery
Page 245
Although soil does not significantly contribute to plant mass, how might it help plants grow?
If a scientist were able to measure the exact mass of carbon dioxide and water that entered a plant, and the exact mass of the sugars produced, would the masses be identical? Why or why not?
What do plants do with all of the carbohydrates they produce by photosynthesis?
Explain how the experiments carried out by van Helmont and Calvin contributed to our understanding of how nutrients cycle in the biosphere.

74. Homework Due on TEST day: All vocabulary from Chapter 8
Chapter 8 Packet
Chapter 8 Mystery
All notes from Chapter 8
Photosynthesis Flip Books
Visual Quiz Worksheet