1. 1. What is photosynthesis? Why is the sun important?
During photosynthesis (PSN), light energy CONVERTED TO chemical energy.
carbon dioxide + water  glucose + oxygen
Most of the energy on Earth comes from the SUN!
Where does other energy on Earth come from?

2. 1. Autotrophs vs. Heterotrophs
most use PSN
convert light energy (sun) to chemical energy (stored in starch and cellulose)
Heterotrophs
have to eat
eat autotrophs and/or heterotrophs
All life ultimately depends on autotrophs.

3. 1. Photosynthetic organisms
plants, algae, cyanobacteria
Endosymbiotic Theory
chloroplasts and mitochondria were small prokaryotes (free-living bacteria)
engulfed (endocytosis) by larger prokaryotes
organelles (double membrane) were formed

4. 2. What is a biochemical pathway?
complex series of reactions
product of one reaction is consumed in the next reaction
link between PSN and cellular respiration (CR)

5. 3. Equation for photosynthesis

6. What are stomata and why are they important to plants?
ATP synthase is a multifunctional protein

7. 4. What are chloroplasts? Chloroplasts cell organelle
site of PSN (light absorbed here)
found in plants and some unicellular eukaryotes (algae)
range in size, number (1 large in algae, 50 small in plant cell)

8. 4. Diagram and structure Outside Inside
TWO membranes (phospholipid bilayers)
endosymbiosis
Inside
thylakoids
system of membranes (phospholipid bilayer as well)
arranged as flattened sacs
grana = stacks of thylakoids (singular = granum)
stroma
solution (goo) that surrounds thylakoids

9. 4. Pigment Chlorophylls located in thylakoid membrane
chlorophyll a and chlorophyll b
chlorophyll a – directly involved in photosynthesis
chlorophyll b – assists chlorophyll a
both allow green light to be reflected and transmitted
carotenoids (accessory pigments) – different patterns of light absorption,
yellow, orange, brown
pigments in flowers and fruits

10. 4. Light absorption Visible spectrum of light
light travels in waves (wavelength = distance between crests)
light can be: transmitted, reflected, absorbed
depends on pigment molecules
ROY G BIV
White – absorbs no light, reflects and transmits all light back to us
Black – absorbs all light, does not reflect and transmit light back to us

11. 5. Electron transport and capturing light energy to “make batteries”
Photosystem (PS)
cluster of pigment molecules (In thylakoid membrane)
PSII and PSI
pre-steps for capturing light
accessory pigments absorb light, energy acquired and passed along
energy reaches a specific pair of chlorophyll “a” molecules

12. Light Dependent Reactions Diagram

13. Step 1
light energy “excites” 2 chlorophyll a electrons in PS II (hey, get moving)
electrons move to outer energy level

14. Step 2 2 electrons LEAVE chlorophyll a in PS II
electrons move to a primary electron acceptor (PEA)
PEA (located in thylakoid membrane) accepts electrons
Oxidation reaction – reactant LOSES one or more electrons, becomes more positive in charge
Reduction reaction – reactant GAINS one or more electrons, becomes more negative in charge

15. Step 3 2 electrons move along electron transport chain (ETC)
energy LOST as electrons move along ETC
energy used to pump protons (hydrogen ions) from the stroma INTO the thylakoid space
proton pump (hydrogen ion pump) = active transport

16. Step 4
electrons
PSI - electrons from chlorophyll a are “excited” (by photons of light) to another PEA
PSII electrons reach PSI, replace the ones PSI lost

17. Step 5 PS I PEA donates electrons to a different ETC
ETC brings electrons to stroma
2 electrons combine with H+ and NADP+ (electron acceptor)
NADPH is made– (“battery” needed to make glucose)
still need to make ATP “battery”

18. 6. Restoring photosystems
Problem: PS II missing 2 electrons
enzyme in the thylakoid space splits water
2H2O  4H+ + 4e- + O2
H+ are left inside the thylakoid (used for ATP synthase)
electrons go into PS II
O2 “waste”

19. 7. Chemiosmosis – MAKING ATP
H+ ion gradient built using hydrogen ion pump
Protons (H+ ions) PUMPED INTO thylakoid space
HIGH protons inside thylakoid space
ATP synthase
ions DIFFUSE OUT of thylakoid through ATP synthase
ATP synthase spins and makes ATP (adds phosphate group to ADP)  ATP “batteries” used to make glucose in stroma
ATP synthase is a multifunctional protein

20. 7. Chemiosmosis
ATP synthase is a multifunctional protein

21. 8. Carbon fixation incorporation of CO2 into organic compounds
Calvin Cycle (C3 pathway, light independent reactions)
occurs in STROMA of chloroplast
most plants use this method
ATP synthase is a multifunctional protein

22. Calvin Cycle (Light Independent Reactions) Diagram
ATP synthase is a multifunctional protein

23. 9. Calvin cycle (C3 pathway)
light independent (no sun needed)
carbon from CO2 “fixed” into organic compounds (carbon fixation)
all steps occurs in the stroma (“goo”) of the chloroplast
TWO “turns” of Calvin Cycle (3 CO2 molecules in at a time)  one glucose
most plants are C3 plants (most plants use the Calvin cycle)
ATP synthase is a multifunctional protein

24. Step 1 6CO2 enters the plant via stomata
6CO2 diffuses into the stroma of the chloroplast
each C attaches to a 5-C compound (RuBP) using an enzyme (RuBisCO)
6-C molecules unstable  C molecules called PGA
ATP synthase is a multifunctional protein

25. Step 2 12 PGA 12 G3P 12 ATP  12 ADP 12 NADPH  12 NADP+
creates 12 G3P (phosphate and H+ ion added to each PGA molecule, phosphate removed)
recycle ADP, phosphate group, NADP+ for light reactions
ATP synthase is a multifunctional protein

26. Step 3 6 C needed to produce one glucose
2 G3P leaves the Calvin Cycle  glucose
10 G3P converted back to 6 RuBP (each has 5 C) (ATP  ADP)
allows Calvin Cycle to continue
ATP synthase is a multifunctional protein

27. 10. Alternative pathways of carbon fixation
used in hot, dry climates
stomata = holes through which plants “breathe” CO2
water loss through stomata
hot climate = stomata closed
prevents water loss
makes CO2 unavailable
ATP synthase is a multifunctional protein

28. 11. C4 pathway (alternative pathway #1)
sugarcane, corn, crabgrass
stomata partially open during the day
CO2 fixed into a 4-carbon compound
lose half as much water as C3 plants, but produce the same amount of carbohydrate
ATP synthase is a multifunctional protein

29. 12. CAM pathway (alternative pathway #2)
cactus, pineapple
stomata only open at night
CAM plants lose the least amount of water
CO2 is fixed into other compounds that can be stored until the sun comes out
very slow growers
ATP synthase is a multifunctional protein

30. 13. Rate of photosynthesis
depends on these three major influences:
light intensity
CO2 availability
temperature
ATP synthase is a multifunctional protein

31. Light intensity
As light intensity increases, the rate of photosynthesis initially increases.
eventually reaches a plateau (maximum rate of photosynthesis)
ATP synthase is a multifunctional protein

32. CO2 availability
As CO2 availability increases, the rate of photosynthesis initially increases.
will reach a plateau
reactions can only occur so fast
ATP synthase is a multifunctional protein

33. Temperature
As temperature increases, the rate of photosynthesis increases up to a certain temperature.
basically a tolerance curve
too hot = stomata close, limits CO2
ATP synthase is a multifunctional protein

34. Chloroplast Diagram
Use the image below to draw a chloroplast. Remember, the image below is of one granum (stack of thylakoids), so the outer membrane chloroplast should be close to the edge of the paper.
Zoom in on the thylakoid membrane and draw and label the following structures: phospholipid bilayer, PSII, molecules that make up the electron transport chain, PS1, proton (H+ ion) pump, ATP synthase
ATP synthase is a multifunctional protein

35. Light Dependent Reactions Diagram – Steps 1, 2, and 3
Summarize the events that take place during Steps 1, 2, and 3 of the light dependent reactions of photosynthesis. Paraphrase the details of each step in the space below. Draw arrows from these details to the correct location on the diagram.

36. Light Dependent Reactions Diagram – Steps 4 and 5
Summarize the events that take place during Steps 4 and 5 of the light dependent reactions of photosynthesis. Paraphrase the details of each step in the space below. Draw arrows from these details to the correct location on the diagram. Also paraphrase the process by which water is split by the enzyme in the thylakoid membrane.

37. Light Dependent Reactions Diagram
Draw the process of light dependent reactions without looking at the diagram. The diagram you draw should be similar to the one we used in class.

38. Light Independent Reactions Steps – 1, 2, and 3
ATP synthase is a multifunctional protein

39. Light Independent Reactions Diagram
Draw the process of light independent reactions without looking at the diagram. The diagram you draw should be similar to the one we used in class.

40. Light Dependent Reactions “Game Pieces”
_____ + _____ + NADP+ (electron acceptor)  NADPH “battery”
2 e- H+
ADP + P (phosphate group) ATP “battery”
4 H+ H+
2 e-
2 e- O2 H+ H+ H+
enzyme splits H2O to restore electrons in PSII and release oxygen
2H2O  _____ _____ _____ H+ H+

41. THYLAKOID MEMBRANE

42. THYLAKOID MEMBRANE

43. CALVIN CYCLE – LET’S FIX CARBON AND MAKE GLUCOSE!
C-C-C-C-C
RuBP
C-C-C-C-C
RuBP
C-C-C-C-C
RuBP
C-C-C
G3P
C-C-C-C-C
RuBP
C-C-C-C-C
RuBP
C-C-C-C-C
RuBP
C-C-C
G3P
C-C-C
G3P
C-C-C
G3P
C-C-C
G3P
C-C-C
G3P
C-C-C
G3P
C-C-C
G3P

44. 12 NADPH  12 NADP+ (12 NADP+ reused in the light dependent reactions)
C-C-C-C-C-C
6-carbon compound
C-C-C-C-C-C
6-carbon compound
12 NADPH  12 NADP (12 NADP+ reused in the light dependent reactions)
12 ATP  12 ADP + 12 P
(12 ADP and 12 phosphate groups are reused in the light dependent reactions)
C-C-C-C-C-C
6-carbon compound
C-C-C-C-C-C
6-carbon compound
C-C-C-C-C-C
6-carbon compound
C-C-C-C-C-C
6-carbon compound
C-C-C
G3P
C-C-C
G3P
C-C-C
G3P
C-C-C
G3P

45. 10 G3P continue to make 6 molecules of RuBisCO (C-C-C-C-C) C-C-C PGA
2 G3P (C-C-C and C-C-C) leave to make glucose (C6H12O6)
C-C-C
PGA
C-C-C
PGA
C-C-C
PGA
C-C-C
PGA
C-C-C
PGA
C-C-C
PGA
6 ATP  ADP + 6 P
(6 ATP needed to make 6 RuBP, 6 ATP and 6 P reused in light reactions
C-C-C
PGA
C-C-C
PGA
C-C-C
PGA

46. Draw the thylakoid membrane. Explain the light reactions to someone.
phospholipid bilayer (0.5 points)
primary electron acceptor (PEA) for photosystem I (0.5 points)
photosystem II (make this the correct color) (0.5 points)
primary electron acceptor (PEA) for photosystem II (0.5 points)
photosystem I electron transport chain (ETC) (0.5 points)
ATP synthase (0.5 points)
photosystem II electron transport chain (ETC) (0.5 points)
thylakoid space (label this location) (0.5 points)
hydrogen ion (proton) pump (0.5 points) (0.5 points
stroma (label this location) (0.5 points)
photosystem I (make this the correct color) (0.5 points)
label the hydrophobic and hydrophilic parts of the phospholipid bilayer (0.5 points)

47. Draw the Calvin Cycle. Explain it to someone.
Start with 6 5-C molecules (RuBP)
use 12 NADPH and 12 ATP when converting PGA  PGAL
6 CO2 enter the Calvin Cycle
use 6 ATP when converting 10 PGAL  6 RuBP
Make one glucose (C6H12O6)