L13: Photosynthesis Flashcards
photosynthesis
conversion of light energy to chemical energy in the synthesis of organic compounds
location: thylakoid membranes of chloroplasts
phototrophs
organisms that convert solar energy to chemical energy in the form of ATP and the reduced coenzyme NADPH
photoheterotrophs
organisms that acquire energy from sunlight but depend on organic sources of reduced carbon
photoautotrophs
organisms that use solar energy to synthesize rich energy molecules from simple organic materials such as CO2 and H2O –> release oxygen as a by-product of photosynthesis
what are the 3 phases of light-dependent reaction?
- light harvesting (capture photons)
- ETC & proton pumping
- ATP synthesis
What are the 2 phases of light-independent reaction?
- carbon assimilation ( Calvin cycle)
- starch and sucrose synthesis
photoexcitation
an electron is excited when it gets struck by a photon of light (the electron is in an excited state, where it jumps to a higher orbital)
structure of chlorophyll
-has a porphyrin ring with magnesium in the middle
(CH3: chlorophyll a/ CHO: chlorophyll b)
-hydrophobic phytol side chain (membrane-bound serves as an anchor)
Mg interaction with the ring changes electron distribution and aids light absorption
phycoerythrin
red pigment
phycocyanin
blue pigment
How does light-harvesting complex & photosystem function
PSI 700nm
PSII 680 nm
light from a photon is absorbed by antenna pigments–> passes along thru resonance energy transfer—> until
e- reaches the reaction center chlorophyll
e- leaves an excited e- and then transferred to an organic acceptor molecule
where are photosystems located?
they are mobile and rearrange themselves between granal and stromal thylakoid membranes
What happens in light-dependent reaction?
Location: thylakoid membrane
H2O—oxidized—> O2
NADP+—-reduced—> NADPH (picks up e-)
ADP+ Pi —-light—-> ATP
Reactants: Products:
h2o o2
ADP+ Pi ATP
NADP+ NADPH
Whar happens in light-independent reaction (Calvin cycle)?
Location: stroma
CO2—–> Glucose
NADPH (gives up e-)—-oxidized—-> NADP+
ATP——> ADP+Pi (give the cycle energy to convert CO2 to glucose)
Reactants: Products:
CO2 Glucose
ATP ADP+Pi
NADPH NADP+
Phases of Calvin Cycle
Phase I: Fixation of CO2 (Rubisco)
Phase II: Reduction of PGA to G3P (PGA Kinase & G3P Dehydrogenase)
Phase III: Regeneration of RuBP from G3P
Calvin Cycle: Phase I
3 molecules of CO2 enters the cycle
(3) CO2 + (3) RuBP —rubisco—> (6) PGA
key: RuBP- Ribulose BIphosphate
PGA - 3-phosphoglycerate
Calvin Cycle: Phase II
3-phosphoglycerate——PGA kinase (ATP->ADP+Pi)——-> (1) 3-biphosphoglycerate
(1) 3-biphosphoglycerate —–G3P dehydrogenase (reduced)—-> G3P
(6) NADPH —oxidized—-> (6) NADPH+
key: G3P- glyceraldhyde-3-phosphate
Calvin Cycle: Phase III
(6) G3P is made
(5) G3P is used to generate RUBP
(1) G3P is converted glucose, fats, amino acids
(5) G3P—(ATP-ADP+Pi)—> (3) RuBP
(3) CO2 —-> (1)G3P
(6) CO2 —-> (2) G3P—–> (1) C6H12O6
(18) 9 ATP —-> 9 ADP+Pi
(12) 6 NADPH —-> 6 NADP+
ETC+ ATP Synthesis Complexes in Thylakoid Membrane
*light particle strike PSII (680)–>excite the e- in the chlorophyll
*chlorophyll loses the e- & flow into the Q cycle
-h2o also loses 2e- to PSII (
(since chlorophyll lost e-, it replenish e- from h2o & oxidize it into O2 gas)==> h2o—oxidized—-> O2
*Q cycle carries the e- into cyct b6-f complex
-while this happens, protons (h+) is pumped into the lumen/inner thylakoid space from the stroma
»_space;>h+ concentration in stroma: down
»_space;>h+ concentration in lumen: up
*the e- continues to PC & transfers e- into PSI (700nm)
*once in PSI, the e- have lost energy, e- in stuck by another photon
*e- goes to Fd (ferrodoxin-iron sulfur)
*from Fd, the e- is carry into NADP reductase
-the e- leave the site, ,meet up with NADP+ & H+
-NADP+ & H+ accepts the e- & is reduced into NADPH
=NADP+ &H+ —reduced—> NADPH
=building a concentration of H+ in the thylakoid space
*due to the concentration gradient of H, they will flow thru ATP synthase to carry out chemosmoisois
-atp synthase will rotate& combine ADP w/ Pi to make atp
Summary:
h20—oxidize—>o2
NADP+ —-reduced (NADP reductase)—-> NADPH
ATP is produced by ATP synthase
***PSII, not PSI, convert H2O into O2
where do starch & glucose synthesize & store in?
chloroplast
where do sucrose synthesize and store in>
cytosol
