Lecture 13: Photosynthetic Electron Transport Flashcards

(33 cards)

1
Q

Photooxidation reactions

A

convert light energy into chem energy

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2
Q

How is photosynthesis similar to ETS?

A

both have linked redox rxnts that generate a proton motive force

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3
Q

What are we oxidizing and reduce to what effect?

A

oxidize H2o to make O2

reduce NADP+ to make NADPH

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4
Q

What is NADHP NOT?

A

an electron source to drive synth of ATP (but it is still an electron carrier, just not used to make ATP)

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5
Q

What are ATP and NADPH chem nrg used for?

A

to convert CO2 to glyceraldehyde-3P in carbon fixation

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6
Q

what are the chem energy formse made by converting sunlight to chem nrg?

A

ATP

NADPH

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7
Q

what pathway does carbon fixation use to convert CO2 to GAP?

A

Calvin cycle

pants make sucrose for food at night

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8
Q

How much of wat do we need to make one molec of glucose?

A

6 H2O
6 CO2
light energy

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9
Q

The delta G value is postive, what does that mean??

where does the energy come from???

A

we are doing the reaction in the reverse direction of glycolysis

the energy comes from light!

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10
Q

Which metabolic pathway runs in the opposite direction of glycolysis and converts glyceraldehyde-3P (GAP) into glucose?

A

gluconeogenesis

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11
Q

What does the photosynethetic electron transport system (PETS) accomplish for the cell?

A

convert light energy into redox nrg

generate ATP by chemiosmosis and reduce NADP+ to make NADPH

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12
Q

What does carbon fixtion (Calvin cycle) accomplish for the cell?

A

the enzymes use nrg from ATP and NADPH to reduce CO2 to make glyceraldehyde-3P (3 carbon carb)

thse carbs are used as chem nrg for mitochondrial respiration

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13
Q

How many ATP used in SIX turns of calvin cycle?

What does 6 turns produce?

A

18 ATP used

GLUCOSE produced

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14
Q

It takes 18 ATP to make a glucose molecule. Is it worth it?

A

YES! because per glucose molecule, you make 30-32 ATP in mitochondrial respiration

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15
Q

key enzymes? (for oxidation )

A
Photosystem II (photoox)
cytochrome b6f (proton pump, like complex 3)
Photosystem I (photoox)
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16
Q

enzyme for photophosphorylation (convert proton motive force into net ATP synth)

A

chloroplast ATP synthase

very much like mitochondrial ATP synthase

17
Q

Key enzyme for CO2 fixation in step 1 of calvin cycle

A

Rubisco
activitiy maximal in light
regulated activity!

18
Q

Examples in real life: DCMU

A

herbicide. blocks electron flow through photosystem II

reduce weeds in non crop areas

19
Q

Examples in real life: paraquat

A

herbicide

prevents reduction of NADP+ by accepting e- from intermediate reductants in PS I

20
Q

key points about photosynthesis

A

e- come from water
excited by light photons
PSII->Q mole—>cytochrome b6f (q cycle from 2e- to 1 e-)–>thylakoid space–>PC–>PSI ( 4 photons light needed for excitement)–>feridoxin–>FAD–>ATP synthase

21
Q

how many protons?

A

8 through cytochrome b6f
4 per 2 water molecules oxidized
total of 12 end up in thylakoid space (and then they go through ATP synthase ad make 3ATP)

22
Q

so what is like NADH in mitochondrial? What drives the movement of protons?

A
Light energy
(redox nrg of NADH used in METS)
23
Q

Chloroplasts

A

3 membranes.
thylakoid membranes in stacks in addition to inner and outer

protons pumped through thylakoid lumen instead

24
Q

stroma

A

space between thylakoid and inner membrane

25
whats product of carbon fixation (calvin cycle)?
GAP | GAP converted into hexose sugar to use as chem nrg at night
26
proton pumping
protons pumped to lumen of thylakoid protons build up here and exit thylakoid through ATP synthase ATP synthesized in stromal space all used in calvin cycle (which is in also in stroma?)
27
which is analogous to he thylakoid membrane: the inner mitochondrial membrane or outer mitochondrial membrane?
inner
28
Flourescence
e- is excited, and then returns to ground state | nothing really accomplished
29
resonance energy transfer
one chlorophyl transfers its energy to another chlorophyl exited state passed down the line e- from first returns to ground state, but another molec has been exciting
30
photooxidation
e- is in excited state redox reaction water oxidized, pheo molec reduced THIS IS WHAT NEEDS TO HAPPEN FOR NRG TRANSFER
31
Z scheme
``` e- start on water move to PSII photon absorption excites e- photoox happens PSI more photons absorbed photoox e- goes to 2NADP to make 2NADPH ```
32
how many photons of light to take 4 e- from water?
8! 1 photon to excite every electron at both PSII and PSI | it happens one at a time
33
What is PC (plastocianin) similar to?
cytochrome C