PHOTOSYNTHESIS L9

Question 1

photoautotrophs

Answer 1

• use sunlight to make organic molecules from CO2

Question 2

photons

Answer 2

• particles of light E

- E inversely proportional to wavelength

Question 3

2 outcomes of energized electrons

Answer 3

1. return to lower orbital (ground state) - emits heat and light
2. leave atom, captured by acceptor - occurs in photosynthesis

Question 4

leaves

Answer 4

• main site of photosynthesis

Question 5

mesophyll cells

Answer 5

• photosynthetic cells

Question 6

chloroplasts

Answer 6

• primary eukaryotic photosynthetic organelle

Question 7

photosynthetic pigment

Answer 7

• captures light E for photosynthesis
• embedded in thylakoid membrane
• ex. chlorophyll a

Question 8

accessory pigments

Answer 8

• absorb wavelength of light not absorbed by chlorophyll a
• widen spectrum of light that can be absorbed
• ex. chlorophyll b, carotenoids

Question 9

why are plants green?

Answer 9

• pigments absorb specific wavelength
• light is not absorbed - its transmitted or reflected
• chlorophyll reflects and transmits green light

Question 10

photosynthetic redox reactions

Answer 10

• H2O oxidized
• CO2 reduced
• endergonic
• E input from sunlight

Question 11

light dependent reactions

Answer 11

• light E turns into chemical E (ATP and NADPH)

- occurs in photosystems

Question 12

photosystems 1&2

Answer 12

• protein complex containing pigments
• in thylakoid membrane
• capture light E
• transfer excited e
• produce ATP and NADPH

Question 13

light harvesting complex

Answer 13

• 250 chlorophyll molecules & accessory pigments, proteins
• transfer E from photon to reaction center

Question 14

reaction center complex

Answer 14

• has pair of chlorophyll a

- transfer e to primary e acceptor

Question 15

PSI

Answer 15

• chlorophyll a
• absorbs best at 700nm
• P700

Question 16

PSII

Answer 16

• chlorophyll a
• absorbs best at 680nm
• P680

Question 17

linear e flow

Answer 17

• light dependent
• PSII then PSI
• produces ATP and NADPH

Question 18

cyclic e flow

Answer 18

• light dependent
• only PSI
• produces only ATP

Question 19

photon absorption (linear e flow)

Answer 19

• 1st step
• photon hits pigment in PSII
• E passed among pigment molecules
• excites P680
• no e moving in this step

Question 20

e transfer (linear e flow)

Answer 20

• 2nd step
• excited e in P680 transferred to primary e acceptor
• P680 is oxidized
• now called P680+
• primary e acceptor reduced
• redox reaction

Question 21

H2O oxidation (linear e flow)

Answer 21

• 3rd step
• P680+ is an extremely strong oxidizing agent
• H2O is oxidized (photolysis)
• e transferred from H to P680+
• H+ released into thylakoid space
• P680+ reduced back to P680
• O2 released as byproduct
• this is where atmospheric O2 comes from

Question 22

electron transport chain (linear e flow)

Answer 22

• 4th step
• e from primary e acceptor goes through ETC from P680 to PSI
• generates H+ gradient

Question 23

ATP synthesis (linear e flow)

Answer 23

• 5th step
• H+ diffuses across thylakoid membrane thought ATP synthase
• drives ATP synthesis

Question 24

PSI E transport (linear e flow)

Answer 24

• 6th step
• light E excites e in pigments
• excites P700
• oxidized to P700+
• primary e acceptor reduced
• P700+ reduced back to P700 by e from ETC

Question 25

PSI ETC (linear e flow)

Answer 25

• 7th step
• e moves through PSI ETC to protein ferredoxin
• no H+ gradient generated
• no ATP produced

Question 26

NADPH synthesis (linear e flow)

Answer 26

• 8th step
• e transfered to NADP+
• NADPH synthesized
• released into stroma
• Calvin cycle
• catalyzed by NADP+ reductase

Question 27

carbon fixation reactions

Answer 27

• formation of carbohydrates from CO2

Question 28

Calvin cycle (C3)

Answer 28

• carbon fixation method used by most plants
• occurs in stroma
• does not directly require light
• does require ATP and NADPH from light dependent reactions