Photosynthesis

Question 1

Photosynthesis equation

Answer 1

6 CO2 + light + 6H20 -> C6H12O6 + 6 O2 + 6 H20

G= 686 kcal/mol

Question 2

Mesophyll cell

Answer 2

Cell that contains chloroplasts; site of photosynthesis

Question 3

Stroma

Answer 3

Fluid inside mesophyll cell; site of Calvin cycle

Question 4

Thylakoid

Answer 4

Stacked chlorophyll-containing sacs inside of mesophyll cell
Thylakoid membrane: site of light reactions
Thylakoid space: site of proton gradient

Question 5

Stomata

Answer 5

Pores in leaf through which CO2 enters and O2 leaves

Question 6

Granum

Answer 6

Stack of thylakoids

Question 7

Light absorption by pigment

Answer 7

Light stays in that state for a short amount of time, then dissipates
Dissipation- some energy is lost as heat
After absorption: fluorescence, heat, or resonance transfer

Question 8

Fluorescence

Answer 8

Emitting a photon lower in energy than what was absorbed

Question 9

Structure of chlorophyll

Answer 9

Porphyrin ring: absorbs photons

Hydrocarbon tail: anchored to thylakoid membrane

Question 10

Absorption spectra

Answer 10

Light waves that are absorbed

Question 11

Action spectrum

Answer 11

Light waves that are used for photosynthesis

Question 12

Endosymbiotic theory

Answer 12

Chloroplasts and mitochondria are of prokaryotic origin

Question 13

Chloroplasts and mitochondria have their own…

Answer 13

DNA, DNA polymerase, RNA polymerase, Ribosomes, Ribosomal RNA

Question 14

Non-cyclic electron transport (light cycle)

Answer 14

H20 split to form 2 electrons -> 2 photons of light excite electrons in photosystem II -> electrons are transferred from P680 to primary acceptor -> plastiquinone -> cytochrome complex, pumping through membrane H+ needed to make ATP -> plastocyanin -> 2 photons of light excite electrons in photosystem I -> electrons are transferred from P700 to primary acceptor -> ferredoxin -> NADP+ reductase reduces NADP+ to NADH

Question 15

Cyclic electron flow

Answer 15

Electrons in PS I -> primary acceptor -> ferredoxin -> cytochrome complex (creates ATP) -> plastocyanin -> PS I
Used when NADP+ is low (plant has been doing lots of photosynthesis)
2 H+ instead of 4 from cytochrome complex: less efficient than non-cyclic transport

Question 16

Amounts of products produced in light reaction

Answer 16

1.5 H+/ photon
4 H+/ ATP
4 photon/ NADPH
Per light reaction: 4 photons, 2 electrons, 6 protons
3 ATP created (2 light cycles)

Question 17

Calvin cycle

Answer 17

Phase 1 (carbon fixation): Rubisco turns 3 CO2 into 3-phosphoglycerate (3PG)
Phase 2 (reduction): 3PG + 6 ATP -> 1,3-bisphosphoglycerate
1,3-BPG + 6 NADPH -reduction> glyceraldehyde 3-phosphate (G3P)
Phase 3 (regeneration): G3P + 3 ATP -> ribulose bisphosphate (RuBP)
Per cycle: 9 ATP and 6 NADH consumed

Question 18

Primitive bacteria

Answer 18

Developed first ATP-driven proton pump

Question 19

Photorespiration

Answer 19

Rubisco adds O2 when CO2 is scarce (much more O2 than CO2 in atmosphere)
Occurs under light conditions
Doesn’t make ATP
C3 plants: 1 in 3 times, rubisco fixes O2 instead of CO2
Decreases photosynthesis
Releases CO2
Increases when stomata close (conserve H2O) and temperatures increase

Question 20

C4 plants

Answer 20

1st stable compound in pathway has 4 carbons
Mesophyll cells, bundle-sheath cells (storage of CO2- impermeable, so it can’t escape), vascular tissue
Spatial separation in pathway

Question 21

C4 photosynthetic pathway

Answer 21

Mesophyll cell: PEP carboxylase -> oxaloacetate -> malate -> pyruvate -> PEP (ATP used to make)
Bundle sheath cell: malate -> CO2 -> Calvin cycle -> sugar transported to vascular tissue
1 extra ATP is used per fixed CO2- as a result, plants use more cyclic electron flow to create more ATP

Question 22

CAM plants

Answer 22

Desert plants
Stomata open at night
Temporal separation in pathway
2 mesophyll cells

Question 23

CAM photosynthetic pathway

Answer 23

Night: PEP carboxylase fixes CO2- creates organic acids
Day: CO2 is used to fuel Calvin cycle and make sugar

Question 24

Photosynthetic rates of plants

Answer 24

C4 > C3&raquo_space; CAM

C4 = 2*C3

Question 25

Antenna complex

Answer 25

Part of thylakoid membrane that contains the most chlorophyll
Photon of light is transferred from chlorophyll molecule to chlorophyll molecule and eventually to reaction center

Question 26

Reaction center

Answer 26

Center of photosystem that contains the special pair of chlorophyll molecules (P680 and P700)
Electrons are transferred from here to primary acceptor