2. CP Ch. 8 PHOTOSYNTHESIS Uses energy from sunlight
Converts water and carbon dioxide from the environment into organic food molecules and oxygen gas

3. Photosynthetic organisms – producers on land and in the water

4. Two Sets of Reactions In chloroplasts Light-Dependent
(“light”) Reactions
- Chlorophyll absorbs sunlight
- Makes energy molecule ATP
- Makes O2 gas

5. 2. Light-independent reactions
Calvin cycle
(“dark” reactions)
Uses energy molecules from light reactions
Uses CO2
Makes glucose
6 CO H2O  C6H12O6 + O2

6. Photosynthesis title, definition and equation.

7. Cells use ATP for energy
ATP - adenosine triphosphate
High-energy bond between phosphate groups
- breaks easily, bond energy is released
- energy is used by cell to do work

8. Transfers ENERGY to new molecule
When a cell needs energy for work, 3rd phosphate comes off ATP and attaches to molecule doing work
Transfers ENERGY to new molecule
“phosphorylate”

9. ATP made in cell respiration ATP used for cellular work
ATP – ADP Cycle
ATP breakdown products (ADP + P) stay in cell
used again to make more ATP when needed
ATP made in cell respiration
ATP used for cellular work
Very fast!! A cell can make 10 million ATP/second

10. Sunlight is white light, containing all colors
                        <>
Sunlight is white light, containing all colors

11. Color of light Depends on wavelength (l) Shorter wavelength
 higher energy
blue-violet end of spectrum
Longer wavelength
 lower energy
red-orange end of spectrum

12. Visible light: small part of Electromagnetic spectrum
travels as a wave ---- behaves as a particle (photon)
Shorter wavelength
Higher energy
Longer wavelength
Lower energy

13. Colors of light absorbed by photosynthetic pigments
Plants absorb blue and red light best

14. Absorption spectrum of chlorophyll a vs action spectrum of photosynthesis. Chlorophyll b is used to ‘fill the gaps’ in the action spectrum.

15. Photosynthetic pigments
Plants have multiple pigments to absorb as much sun energy as possible
Chlorophyll a is the primary pigment – starts the chain of reactions
Chlorophyll b, carotenes, xanthophylls and others are accessory pigments.
They absorb wavelengths that chlorophyll a cannot absorb  use more of sunlight

16. Separates a liquid mixture by solubility
Chromatography
Separates a liquid mixture by solubility

17. Absorbed light energy is transferred to electrons in pigment
Colors of light absorbed by a chloroplast
Colors NOT absorbed are reflected or transmitted
-- the colors we SEE
Absorbed light energy is transferred to electrons in pigment
-- energized electrons
Chlorophyll absorbs mostly from the red and blue ends of the spectrum reflects green.

18. Parts of a chloroplast Thylakoid membranes - have chlorophyll
- absorb sunlight
- site for 1st set of reactions
Granum – stack of thylakoid sacs
Stroma – fluid surrounding thylakoids
- site for 2nd set of reactions

19. Parts of a Leaf

20. Electron carriers
Coenzymes - carry H+ ions and electrons (H atoms) – take from one molecule in a chain of reactions, - give them to another molecule in a later reaction
In photosynthesis, carrier is NADP
helps change sunlight to chemical energy
takes electrons and H+ ions from water
Gives them to CO2  makes glucose

21. Carries (accepts) e- and H+ ions
NADP  NADPH  NADP
Carries (accepts) e- and H+ ions

22. Light –dependent reactions In thylakoid membranes
#1. Chlorophyll absorbs sunlight
Electrons from chlorophyll
Make ATP

23. #2. Light Splits Water H2O  2 H+ + 2 e- + O
Hydrogens (H+) go to NADP  NADPH
Oxygens  make O2 gas
Electrons - replace electrons lost from chlorophyll

24. Light Reactions reactant products
Water
ATP
NADPH
Oxygen gas
Also need
Sunlight
chlorophyll

25. How does light energy change to ATP?
Light excites electrons
Electrons start a series of reactions
Electron Transport Chain
Makes ATP

26. Electron Transport Chain makes ATP
1. Electron energy concentrates H+ ions
2. Ions diffuse through a membrane enzyme
3. Enzyme makes ATP

27. Making ATP

28. ATP Synthase Enzyme In thylakoid membrane H ions move through it
Adds P to ADP
Makes ATP
chemiosmosis

29. Summary of Light reactions
1. Capture light energy, make ATP
Split water (H2O) into 2 H+ + O + 2e-
Electrons replace those lost from chlorophyll
O makes oxygen gas
3. H+ and e- go to NADP  NADPH
1) Later they become part of glucose molecule

30. Light Reactions make: ATP NADPH O23 1 2

31. See oxygen gas made by an aquatic plant

32. Light-Independent Reactions “Dark” reactions, or Calvin Cycle
In stroma of chloroplast
Uses ATP made in light reactions
Fixes CO2 from air
Adds H+ ions and electrons from water
Makes GLUCOSE

33. CO2 from air becomes part of organic molecule
What is carbon fixing?
CO2 from air becomes part of organic molecule
Energy needed to make glucose comes from ATP made in the light reactions

34. Calvin Cycle 2) Joins to CO2 ”fixed” in stroma
1) Start: 5-carbon compound in stroma
3) ATP and NADPH are used
5) End: Stroma compound returned
4) glucose made

35. Overview of Photosynthesis

36.  Photosynthesis uses light energy to make food molecules
Chloroplast
CO2
Light
4. “Fixes” carbon
NADP+
ADP
1. Absorbs light energy  P
LIGHT
REACTIONS
CALVIN
CYCLE
(in stroma)
5. Uses energy molecules made in light
(in thylakoids)
2. Makes ATP, NADPH
ATP
Electrons
NADPH
3. Light splits water -makes O2
6. Makes glucose
Starch
Lipids O2
Sugar
proteins
cellulose

37. Environmental Factors affecting Photosynthesis
Light – bright sun, more energy
a. Long days (summer), more light absorbed
b. Wavelength – cannot absorb green light

38. How amount of light affects rate of photosynthesis
plateau
At high light intensity, rate stays constant because all chlorophyll are being used
Light intensity affects rate of photosynthesis.
At low light intensity, rate increases as light increases

39. Factors Affecting Photosynthesis
2. Temperature – warm, but not too hot
a. Hot days – stomata close to save water
3. Water – soil must be moist
Water comes up through xylem in veins
Exits through open stomata
Water low? – stomata close

40. How temperature affects rate of photosynthesis
Rate drops above optimum temp
stomata close to save water
enzymes denature
Rate increases with increasing temp (energy)
- To optimum
Temperature affects the rate of photosynthesis. Remember enzyme theory.
Enzymes used in respiration: rubisco is the main one. ATP synthase can also be denatured.

41. How CO2 concentration affects rate of photosynthesis
plateau
At high CO2 concentration, rate is constant because all coenzymes are being used
CO2 affects rate of photosynthesis. CO2 is the substrate in carbon fixation (Calvin cycle) – rubisco is the enzyme.
At low CO2 concentration, rate increases as CO2 increases

42. Ordinary plants in hot weather
C-3 – carbon fixed into a 3-carbon compound
In hot, dry weather, C-3 plants:
leaf openings close to save water
How can CO2 get inside?
Leaf epidermis, stomata

43. Guard cells open/close stomata
Open Closed
Close when [CO2] or water is low in plant

44. C-4 Plants Corn Sugar Cane crabgrass
C-4 plants store CO2 while stomata are open
- use stored carbon when stomata are closed
 Can still make sugar
Corn Sugar Cane crabgrass

45. CAM Plants
Succulents cacti pineapples
Fix CO2 during the night, when it is cool enough for open stomates
- Do photosynthesis during the day, using the stored carbon

46. Parasitic plants Supplement nutrition by taking from other organisms
Dodder Plant
Cannot make its own food
Takes nutrients from host plant

47. Mistletoe – supplements photosynthesis

48. Carnivorous plants Eat insects to get nitrogen
Venus Fly Trap
Insect walking on leaves touches trigger hairs
- Leaves close, insect digested

49. Pitcher plant Insect climbs inside, can’t get out
Walls of tube are slippery

50. Sundew – eats insects Sugary “dew” attracts insects
Insects get stuck, plant closes

51. Carotenes in nature
We can see carotenes, xanthophylls, and other pigments in places other than autumn leaves