PHOTOSYNTHESIS

Question 1

Chlorophyll biosynthesis

Answer 1

Protoporphyrin IX: a precursor of
Mg-containing chlorophyll and Fe-containing heme

Question 2

Photo excitation outcomes

Answer 2

Heat
Thermal dissipation: converting excitation energy to heat
Chlorophylls return to ground state
Fluorescence: immediate reemission of energy as a long wavelength
Energy transfer: excited pigment molecule (e.g. chlorophyll) transfers it energy to another molecule
Photochemistry: energy of the excited state triggers a
chemical reaction and becomes an e- donor. Linkage of the excited e-donor to a proper e-acceptor.Transduction of chemical energy

Question 3

Energy transfer

Answer 3

Pure physical phenomenon
No chemical changes
Resonance energy transfer: energy is
transferred from pigment to pigment by
resonance until it reaches the reaction
center pigment

Question 4

light-harvesting complex

Answer 4

pigments molecules bounded to proteins

Question 5

reaction center

Answer 5

special pair of chlorphyll a
electron acceptor

Question 6

PSII and PSI

Answer 6

thylakoid membranes
electron transport chain connects

Question 7

P680+

Answer 7

PSII
strong oxidant
pull electrons from H20

Question 8

p700

Answer 8

PSI
strong reductant
donates electrons to NADP+

Question 9

Z-scheme

Answer 9

cooperation of PSII and PSI in the transfer of electrons from water to NADP+

Question 10

PC

Answer 10

small protein and mobile electron carrier

Question 11

PQ

Answer 11

small molecule and mobile electron carrier

Question 12

LCHII complex

Answer 12

PSII
oxygen-evolving complex on PSII luminal surface

Question 13

transfer of electrons

Answer 13

from H2O to NADPH

Question 14

Photophosphorylation

Answer 14

ATP synthesis
chloroplast (thylakoid space)
energy: light
Electron: H2O
Direction of proton pumping –into the thylakoid space of the chloroplasts
-Movement of protons during ATP synthesis –out of the thylakoid space in photosynthesis

Question 15

Linear electron transport

Answer 15

H2O to NADPH
involved PSII, cyc b6f, PSI
product: NADPH and ATP

Question 16

Cyclic electron transport

Answer 16

electrons cycle (no net production)
involves cyc b6f and PSI
product: ATP

Question 17

Water-water cycle

Answer 17

H2O to H2O
involves PSII, cyc b6f, PSI
product: ATP

Question 18

Mitchell’s chemiosmotic theory

Answer 18

The electron transport chain
generates proton-motive force
for ATP synthesis
- Eis small, and pis determined
entirely by pH

Question 19

excess excitation

Answer 19

photo-oxidative damage

Question 20

excess light

Answer 20

non photochemical quenching (heat)
energy-dependent quenching (qE): The xanthophyll cycle
State transition (qT): Conformational changes in LHCII
Photoinhhibition(qI): Light-induced reduction in quantum yield as a consequence of damage

Question 21

ZE

Answer 21

stroma
low light/ high luminal pH

Question 22

VDE

Answer 22

lumen/ low luminal pH

Question 23

DI protein

Answer 23

subunit of PSII
susceptible to photodamge

Question 24

factors affecting the rate of photosynthesis

Answer 24

Light intensity
CO2 concentration
temperature

Question 25

The rate of net photosynthesis is saturated at higher light intensities. Why?

Answer 25

At the light saturation point, photosynthetic reaction rate is determined by light-independent reactions(Carbon fixation)

Question 26

At low light intensities, the relationship between net photosynthesis and light intensity is linear. Why?

Answer 26

At low light intensities, light is limited for photosynthesis

Question 27

At low light intensities, there is a negative value of net photosynthesis. Why?

Answer 27

Plants have mitochondria and respire, consuming O2 and producing CO2. In the dark, CO2production is greater than CO2 consumption

Question 28

CO2 concentration

Answer 28

C4 plants have lower compensation point than C3 plants: Photorespiration is suppressed by the CO2 concentrating mechanism in C4 plant

Question 29

Starch

Answer 29

storage carbohydrate chloroplast

Question 30

Sucrose

Answer 30

Principle photosynthetic product in plants cytoplasm

Question 31

Starch enzymes

Answer 31

Starch synthetase Fructose-1,6-bisphosphatase Sucrose phosphate synthase

Question 32

Amylose

Answer 32

α-1,4-glycosidic bond linear chain (straight chain of glucose)

Question 33

Amylopectine

Answer 33

α-1,6-glycosidic bond highly branched

Question 34

Key enzymes for hydrolytic starch degradation

Answer 34

α-Amylase: Targeting endo α-1,4-glycosidic bonds β-Amylase: Targeting exoα-1,4-glycosidic bonds at the non-reducing end of starch chains by cleaving off two glucose molecules (maltose) Limit dextrinase(pullulanase): Targeting the branch point of starch (α-1,6-glycosidic bonds)

Question 35

Sucrose synthesis

Answer 35

Sucrose 6-phosphate synthase Sucrose 6-phosphate phosphatase Sucrose is synthesized in cytosol

Question 36

Triose phosphate

Answer 36

Both sucrose and starch are synthesized

Question 37

Sucrose Degradation

Answer 37

Invertase Irreversible catalysis for sucrose degradation

Question 38

Generation of UDP-glucose for cell wall biosynthesis during sucrose degradation