L13: Photosynthesis

Question 1

photosynthesis

Answer 1

conversion of light energy to chemical energy in the synthesis of organic compounds
location: thylakoid membranes of chloroplasts

Question 2

phototrophs

Answer 2

organisms that convert solar energy to chemical energy in the form of ATP and the reduced coenzyme NADPH

Question 3

photoheterotrophs

Answer 3

organisms that acquire energy from sunlight but depend on organic sources of reduced carbon

Question 4

photoautotrophs

Answer 4

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

Question 5

what are the 3 phases of light-dependent reaction?

Answer 5

1. light harvesting (capture photons)
2. ETC & proton pumping
3. ATP synthesis

Question 6

What are the 2 phases of light-independent reaction?

Answer 6

1. carbon assimilation ( Calvin cycle)
2. starch and sucrose synthesis

Question 7

photoexcitation

Answer 7

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)

Question 8

structure of chlorophyll

Answer 8

-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

Question 9

phycoerythrin

Answer 9

red pigment

Question 10

phycocyanin

Answer 10

blue pigment

Question 11

How does light-harvesting complex & photosystem function

Answer 11

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

Question 12

where are photosystems located?

Answer 12

they are mobile and rearrange themselves between granal and stromal thylakoid membranes

Question 13

What happens in light-dependent reaction?

Answer 13

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

Question 14

Whar happens in light-independent reaction (Calvin cycle)?

Answer 14

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+

Question 15

Phases of Calvin Cycle

Answer 15

Phase I: Fixation of CO2 (Rubisco)
Phase II: Reduction of PGA to G3P (PGA Kinase & G3P Dehydrogenase)
Phase III: Regeneration of RuBP from G3P

Question 16

Calvin Cycle: Phase I

Answer 16

3 molecules of CO2 enters the cycle

(3) CO2 + (3) RuBP —rubisco—> (6) PGA

key: RuBP- Ribulose BIphosphate
PGA - 3-phosphoglycerate

Question 17

Calvin Cycle: Phase II

Answer 17

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

Question 18

Calvin Cycle: Phase III

Answer 18

(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+

Question 19

ETC+ ATP Synthesis Complexes in Thylakoid Membrane

Answer 19

*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
&raquo_space;>h+ concentration in stroma: down
&raquo_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

Question 20

where do starch & glucose synthesize & store in?

Answer 20

chloroplast

Question 21

where do sucrose synthesize and store in>

Answer 21

cytosol