Unit 2 - Light Dependent RXN

Question 1

Photosynthesis occurs in two stages

Answer 1

1) photo stage
2) synthesis stage

Question 2

Photo stage

Answer 2

• light-dependent rxn
• occurs in thylakoid membranes in chloroplast
• energy ficing
• converts light energy to make ATP and NADPH which will be used to drive the next stage

Question 3

Synthesis stage

Answer 3

• dark light independent rxn
  (calvin cycle)
• carbon fixing reactions
• uses ATP to convert inorganic mols to organic fuel containing stored potential energy in the bonds

Question 4

Photosynthesis light independent / dark reaction

Answer 4

= calvin cycle

Question 5

photosynthesis light reaction goes on to become

Answer 5

1) cyclic - PS1 only - makes ATP
2) noncyclic - PS2 and PS1 - makes ATP and NADPH

Question 6

Summary of rxn

Answer 6

light - chemical energy, ATP or NADPH (through light dependent reaction) - chemical energy (through calvin cycle)

Question 7

light reaction of photosynthesis can occur in 2 ways

Answer 7

noncyclic and cyclic photophosphorylation

Question 8

both cyclic and non cyclce use chlorophyll…

Answer 8

which sits near an electron acceptor in a photosystem (cluster of proteins and pigments embedded in the thylakoid membrane)

Question 9

Non-cyclic photophosphorylation makes

Answer 9

ATP ad NADPH

Question 10

4 major protein complexes

Answer 10

1) photosystem 2 (PS2)
2) cytochrome complex (cyt)
3) photosystem 1 (PS1)
4) NADP+ reductase
5) ATP synthase

Question 11

3 major electron shuttles

Answer 11

1) plastoquinone
2) plastocyanin
3) ferredoxin

Question 12

divide 3 parts

Answer 12

1) photoexcitation
2) electron transport
3) chemiosmosis

Question 13

photoexcitation

Answer 13

absorption of a photon by an electron by chlorophyll

Question 14

electron transport

Answer 14

creates an H+ reservior

Question 15

chemiosmosis

Answer 15

movement of protons to help phosphorylate ADP to ATP

Question 16

Photoexcitation pt 1

Answer 16

the actions of photosystem 2 begin when a photon energizes an e- in P680 forming P680*

Question 17

Photoexcitation pt 2

Answer 17

the energized chlorophyll (P680) then transfers the high energy e- to acceptor A in the reaction centre. P680 is now + charged

Question 18

Photoexcitation pt 3

Answer 18

the + P680 ion then oxidized water and the high energy e- is transferred from the reaction centre to the carrier mol plastoquinone (PQ)

Question 19

What has just been release and where

Answer 19

oxygen gas and protons r now released into the human

2water = 4H + 4e- + O2

Question 20

Linear Electron Transport and ATP Synthase: 1) Oxidation of P680

Answer 20

the absorption of light energy by photosystem 2 results in the formation of an excited state P680 mols which is rapidly oxidized transferring a high energy electron to the primary acceptor

Question 21

Linear Electron Transport and ATP Synthase: 2) Oxidation-reduction of plastoquinone

Answer 21

from the primary acceptor the ET to PQ which shuttles e- from PS2 to the cytochrome complex. as PQ accepts e- from PS3, it picks up protons (H+) from the stroma and then releases them into the luman as it donates e- to the cytochrome complex (H+ increases in lumen)

Question 22

Linear Electron Transport and ATP Synthase: 3) ET from cytochrome complex and shuttling by plastocyanin

Answer 22

plastocyanin shuttles the e= from cytochrome complex to photosystem 1

Question 23

Linear Electron Transport and ATP Synthase: 4) Oxidation-Reduction of P700

Answer 23

as PS1 absorbs additional light energy, the e- bc excited. this cause the excited e- to escape photosystem moving along a second ETC

Question 24

Linear Electron Transport and ATP Synthase: 5) ET to NADP+ by Ferredoxin

Answer 24

first e- is transported by a sequence of carriers within photosystem 1, transferred to ferredoxin. the oxidation of ferredoxin results in the transfer of e- to NADP+ reducing to NADP

Question 25

Linear Electron Transport and ATP Synthase: 6) The Formation of NADPH

Answer 25

a 2nd e- is transferred to NADP by another mol of ferredoxin. this 2nd e- and proton (H+) from the stroma r added to NASP by the SANP+ reductase to from NADPH

Question 26

Chemiosmotic Synthesis of ATP

Answer 26

proton gradient is established across the thylakoid membrane by 3 mechanisms

Question 27

Chemiosmotic Synthesis of ATP (1)

Answer 27

protons (H+) r taken into the lumeb by the redox of plastoquinone as it moves from PS2 to the cytochrom complex and back again

Question 28

Chemiosmotic Synthesis of ATP (2)

Answer 28

the conc. of H+ inside the lumen is increased by the addition of 3 protons for each water mol that is split in the lumen

Question 29

Chemiosmotic Synthesis of ATP (3)

Answer 29

the removal of one H+ from one stroma from each NADPH mol formed decreases the con. of H+ in the stroma outside the thylakoid

Question 30

proton gradient

Answer 30

high conc. of ions in the LUMEN and a low conc. of ions in the STROMA

Question 31

chemiosmosis

Answer 31

the H+ ions flow down their concentration gradient through a protein complex of ATP synthase which is embedded in the membrane releasing energy in the process

Question 32

Cyclic Photophosphorylationmakes

Answer 32

involves PS1 only and ONLY ATP is created

Question 33

Cyclic Photophosphorylation 3 major protein complexes

Answer 33

1)photosystem 1 2)cytochrome complex 3)ATP synthase

Question 34

Cyclic Photophosphorylation 3 electron shuttles

Answer 34

1)plastoquinone (PQ) 2)plastocyanin (PC) 3)ferredoxin (FD)

Question 35

Cyclic Photophosphorylation pathway

Answer 35

- uses photosystem 1 (P700) but not photosystem 2 (P680) - electrons move in a circular pathway from P700, FD, PQ, cytochrom complex, and plastocyanin and back to P700

Question 36

Products of Cyclic Photophosphorylation

Answer 36

- makes ATP - make NO NADPH and O2 - calvin cycle needs more ATP then NADPH - cyclic ET produces ATP mols needed for the redution of CO2 in Krebs

Question 37

Electron Movement

Answer 37

photosystem 1 absorbing light energy exciting P700 to P700* gives up an electron to the primary electron acceptor and becomes P700*

Question 38

P700*

Answer 38

receives e- from plastocyanin and returns to neural P700

Question 39

e- passes through

Answer 39

1) ferredoxin 2) ES plastoquinone 3) cytochrome complex (pumps protons into lumen) 4) plastocyanin and then repeats

Question 40

in short NONcyclic (5)

Answer 40

1) uses PS1 and 2 2) photolysis of water is needed 3) oxygen is evolved 4) NADPH is synthesized 5) production used for light independent rxn

Question 41

in short cyclic (5)

Answer 41

1) ONLY PS1 2) water not needed 3) no oxygen 4) NADPH is not synthesized 5) used to make additional ATP inorder to meet cell energy demands

Question 42

what is the energy of a photon first used to do in photosynthesis

Answer 42

energize an e-

Question 43

which mol absorbs the energy of a photon in photosynthesis

Answer 43

chlorophyll

Question 44

plants make O2 when they photosynthesize. Where does O2 come from

Answer 44

splitting water mols

Question 45

which colours of light does chlorophyll a repeal

Answer 45

green