1. PHOTOSYNTHESIS

2. PHOTOSYNTHESIS Process that converts light energy to chemical energy
Occurs in chloroplasts of green plants (mostly in leaves)
Contains pigment called chlorophyll
Gives chloroplasts their green color

3. Chloroplast Thylakoid stacks are connected together
Organelle where photosynthesis takes place.
Stroma
Outer Membrane
Thylakoid
Granum
Inner Membrane
Thylakoid stacks are connected together

4. CHLOROPLAST STRUCTURE
Enclosed by two membranes
Inner membrane encloses a thick fluid called stroma
Disk-shaped sacs called thylakoids are suspended in stroma
Granum: stack of thylakoids

5. PHOTOSYNTHESIS EQUATION
SUN
6 CO H2O  C6H12O6 + 6 O2
6 carbon dioxide + 6 water  glucose oxygen
Occurs in two main stages:
1. light reactions: happens in thylakoid membranes
2. Calvin cycle: happens in the stroma

6. C6H12O6 + 6 O2  6 CO2 + 6 H2O + ATP Photosynthesis Equation:
sunlight
6CO2 + 6 H2O  C6H12O6 + 6 O2
6 Carbon Dioxide Water  Glucose Oxygen
Cellular Respiration Equation:
C6H12O6 + 6 O2  6 CO H2O + ATP
Glucose Oxygen  6 Carbon Dioxide Water

8. The Light Reactions Convert energy in sunlight to chemical energy
Chlorophyll molecules capture light energy (units called photons)
Captured energy is used to split water molecules  photolysis
H2O  O2 and H+ ions produced

9. The Light Reactions O2 escapes from leaf as waste product
H+ bonds to NADP+ (electron carrier molecule) forming NADPH
NADPH moves to stroma
ATP is produced by light energy

11. The Calvin Cycle
Glucose made from atoms of CO2, hydrogen, ATP, and electrons carried by NADPH
Enzymes for Calvin cycle reactions are located outside thylakoids  dissolved in stroma
ATP from light reactions provides energy to make glucose

12. The Calvin Cycle
Calvin cycle reactions are also called the light-independent or dark reactions (can occur without direct light)
Cannot continue indefinitely without two inputs supplied by light reactions:
1. ATP
2. NADPH

15. LIGHT ENERGY & PIGMENTS
Visible light: part of the electromagnetic spectrum our eyes detect as different colors
Pigments: chemicals that absorb, transmit, or reflect different wavelengths of light

16. CHLOROPLAST PIGMENTS Absorb blue-violet & red-orange light
Convert absorbed light energy to chemical energy
Green pigments do not absorb green light well:
reflect or transmit it back
makes leaves look green

18. LIGHT REACTIONS & PHOTOSYSTEMS
Photosystems: clusters of chlorophyll and other molecules in thylakoid membranes of the chloroplast
Two photosystems involved in light reactions
Each photosystem uses a different chlorophyll molecule and performs a different task
Electron transport chain connects the two photosystems and produces ATP

20. PHOTOSYSTEM 2 “Water-splitting” photosystem
Produces hydrogen ions (H+) and releases oxygen (O2) as a waste product
Electrons released in splitting H2O are used to make ATP

21. PHOTOSYSTEM 1 “NADPH producing” photosystem
Light striking another chlorophyll molecule causes electrons to gain energy and leave the molecule
These electrons along with H+ ions from water are added to NADP+ to produce NADPH

23. What you need to know about the light reactions
Occur on thylakoid membranes
Get energy from photons of light
Reactants: H2O, light
End products: O2, NADPH, ATP
Destination of end products:
ATP and NADPH go to stroma (Calvin cycle)
O2 leaves as waste product

24. What you need to know about the Calvin Cycle
Uses CO2 and a 5-carbon sugar (RuBP) along with molecules from the light reactions (ATP & NADPH) to produce glucose—the main cellular fuel
Occurs in the stroma of chloroplast
Where do the reactants come from?
RuBP  present in stroma
CO2  from atmosphere
NADPH, ATP  from light reactions

25. CALVIN CYCLE What are the end products?
3-carbon sugar G3P  used by plant cells to produce more complex carbohydrates
Glucose
starch
cellulose
Where does energy for Calvin cycle come from?
ATP produced in light reactions
Where does the Calvin cycle occur?
stroma of chloroplast

26. SUMMARY OF PHOTOSYNTHESIS

27. THE CARBON CYCLE
Process by which carbon moves from inorganic to organic compounds and back
Photosynthesis converts inorganic carbon dioxide to organic compounds
Consumers eat producers and return carbon dioxide to the atmosphere via cellular respiration

28. CARBON CYCLE

29. PHOTOSYNTHESIS & GLOBAL CLIMATE
Photosynthesis uses CO2 to make sugars
Most organisms give off CO2 in cellular respiration
Total effect of all the organisms on Earth has a large effect on the amount of CO2 in the atmosphere

30. Greenhouse Effect
Amount of CO2 in atmosphere has been increasing rapidly
greenhouse effect: CO2 traps heat from the sun that would otherwise escape into space
Increased CO2—mainly from fossil fuels—traps more heat leading to global warming

31. GREENHOUSE EFFECT