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Biochem 385 Unit 1 > Lecture 13: Photosynthetic Electron Transport > Flashcards

Lecture 13: Photosynthetic Electron Transport Flashcards

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
Q

whats product of carbon fixation (calvin cycle)?

A

GAP

GAP converted into hexose sugar to use as chem nrg at night

26
Q

proton pumping

A

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
Q

which is analogous to he thylakoid membrane: the inner mitochondrial membrane or outer mitochondrial membrane?

A

inner

28
Q

Flourescence

A

e- is excited, and then returns to ground state

nothing really accomplished

29
Q

resonance energy transfer

A

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
Q

photooxidation

A

e- is in excited state
redox reaction
water oxidized, pheo molec reduced

THIS IS WHAT NEEDS TO HAPPEN FOR NRG TRANSFER

31
Q

Z scheme

A 
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
Q

how many photons of light to take 4 e- from water?

A

8! 1 photon to excite every electron at both PSII and PSI

it happens one at a time

33
Q

What is PC (plastocianin) similar to?

A

cytochrome C

Biochem 385 Unit 1 (13 decks)

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