– Photosynthesis is the process by which certain organisms use light energy
• To make sugar and oxygen gas from carbon dioxide and water
Light energy
6 CO
2
+ 6
Carbon dioxide
H
2
O
Water
PHOTOSYNTHESIS
C
6
H
12
O
6
Glucose
+ 6 O
2
Oxygen gas
• What does it need? (Input)
• What does it make? (Output)

• Autotrophs 
Producers of the biosphere:
– produce organic molecules from CO
2
& inorganic raw materials
• Heterotrophs  consumers

1. Describe Oxidation & Reduction reactions

• Oxidation
– When a compound loses electrons
• Reduction
– When a compound gains electrons
• CO
2
+ H
– CO
2
2
O + energy → C
6
H
12
O
6 is reduced to form glucose
– Water is oxidized to form O
2
+ O
2

•Photosynthesis is a redox process, as is cellular respiration
– In photosynthesis
• H
2
O is oxidized and CO
2 is reduced
Reduction
6 CO
2

6 H
2
O C
6
H
12
O
6

6 O
2
Oxidation
Oxidation
C
6
H
12
O
6

6 O
2
Figure 7.4A, B
6 CO
2
Reduction

6 H
2
O

• If H2O is losing electrons than it is being reduced/oxidized
• Co2 is being reduced/oxidized, which means it is gaining/losing electrons.

• Light reactions
– Depend on light
– Occur in Thylakoid
Membrane
• Light Independent
(“Dark”) reactions
– Does NOT need light
– Occurs in the Stroma

12.Compare & contrast the structure & function of mitochondria & chloroplast
15. Determine what factors affect the process of photosynthesis & cellular respiration

Where does the Light Dependent Reaction occur?
The Light Independent reaction?

• Found in mesophyll
– 1 mesophyll cell may have 30 chloroplasts
• Stomata regulate passage of CO
O
2 and H
2
O
2
,

Where does the
Light Dependent
Reaction occur?
• What factors could affect the process of photosynthesis?
The Light
Independent reaction?

11. Describe the purpose of Chlorophyll
& Accessory pigments.

• Pigments
– Absorb light energy
– Boost e  become unstable!
• Chlorophyll
– Chlorophyll a  main pigment  blue-green
– Chlorophyll b  accessory pigment  yellow-green
• Other accessory pigments  absorb different wavelengths of light
– Carotenoids  yellow-orange
– Xanthophyll  yellow
– Rhodophyll  red
– Fucoxanthin  brown

• Pass energy  reaction center
(chlorophyll a molecule)  transfers energy to primary electron acceptor
• antenna pigments are primarily chlorophyll b, carotenoids & xanthophyll

• What is the purpose/function of pigments?

• Light reactions
– light energy  chemical energy (ATP and
NADPH) and produce
O
2
• Light Independent
(“Dark”) reactions
– Using ATP and
NADPH from the light reactions
 form sugar from
CO2

6. Explain how electron transport chains
(ETC) establish an electrochemical gradient across membranes.
7. Contrast Chemiosmosis in Cellular
Respiration and Photosynthesis

• Powers ATP synthesis in light reactions
• electrons (e-) are passed along a chain of proteins
(called the ETC) in the membrane  H+ pumped into Thylakoid space (chemiosmosis)
• H + diffuse back across the membrane through
ATP synthase  powers the phosphorylation of
ADP to produce ATP (photophosphorylation)

Photophosphorylation http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm

• ETC uses the energy of e- being passed along to pump _______ from the
________ into the thylakoid _______
• Chemiosmosis is the movement of
______ to create a
________concentration.

3. Identify the inputs and outputs and location of the light reactions and Calvin
Cycle.
4. Explain the role of NADH, FADH2, and
NADPH.
14. Summarize how energy is transferred during photosynthesis and cellular respiration.

• NAD+
– Reacts with C-H bonds to become
NADH
• NADP+
– Reacts with free e- and H+ ions
• ADP  ATP
– diffusion of H+ through ATP Synthase

• Inputs?
• Outputs?
• Two types:
– Noncyclic
Photophosphorylation
– Cyclic
Photophosphorylation

Learning Target
12. Describe the connection between
PS2 & PS1

LIGHT
H
2
O CO
2
NADP +
ADP
LIGHT
REACTOR
ATP
NADPH
CALVIN
CYCLE
STROMA
(Low H + concentration)
O
2
Photosystem II
2 H +
Pq
2
[CH
2
O] (sugar)
Cytochrome complex
Light
Photosystem I
Fd
NADP + reductase
3
NADP + + 2H +
NADPH + H +
Pc
THYLAKOID SPACE
(High H + concentration)
H
2
O
1
1 ⁄
2
O
2
+2 H +
2 H +
To
Calvin cycle
STROMA
(Low H + concentration)
Thylakoid membrane
ATP synthase
ADP
P
H +
ATP

Light Dependent RXN animation
• http://www.science.smith.edu/department s/Biology/Bio231/ltrxn.html
• http://vcell.ndsu.nodak.edu/animations/ph otosynthesis/movie-flash.htm

• Primitive  used by bacteria
• Electron boosted out of
P1  ETC  returned to P1
• Electron drives proton pumps  chemiosmosis
 ATP

3. Identify the inputs and outputs and location of the light reactions and Calvin Cycle.
4. Explain the role of NADH, FADH2, and
NADPH.
15. Summarize how energy is transferred during photosynthesis and cellular respiration.

• Occur in the dark or the light
• Light independent reactions
• 3 steps
– Carbon fixation
– Reduction
– Regeneration of RuBP

• RuBP (ribulose bisphosphate)
– 5 C sugar
– Catalyzed by Rubisco
(RuBP carboxylase)
– Adds CO
2
• Creates an unstable 6
C molecule that splits
• Creates PGA (3 C moleucle

• PGA gets phosphorylated by
ATP (gets it’s energy)
• Reduced by NADPH
(gets it’s e-)
• Produces G
– some G
3
3
P (PGAL)
P  glucose
– most G
3
P  regenerate RuBP

• 1 G
3
P moves out to eventually become glucose
• G
3
P  rearranged into RuBP
• Requires input of 3
ATP
• Takes 6 turns of cycle  1 glucose

http://www.science.smith.edu/departments/Biology/Bio231/calvin.html

• C
3 plants  rice, wheat, soybeans
• Uses Co
2 directly to make PGA
• On hot, dry days they close their stomata
– no CO
2 taken in and O
– rubisco substitutes O
2
2 builds up for CO
– Creates a 2 C compound
2
• 2 C compound gets broken down  releases
CO
2
& water
• Called photorespiration
– Uses light, releases CO
2
– Doesn’t make glucose and water

4
• Sunny ecosystems
• C is fixed into 4 C molecule
• Carbon fixed outside cells (in bundle sheath cells  very efficient  requires extra ATP
• Only fixes C, not oxygen
• Donates the carbon to Calvin
Cycle
• Balances out photorespiration
& saves water
• Corn and sugarcane are a C
4 plants

• Crassulacean acid metabolism  Hot/dry climates
• Orchids, cacti, pineapple etc.
• Stomates open at night to reduce water loss  evaporation
• CO
2 is fixed into a 4 C compound, used later