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Biochemistry > Lecture 19 & 20 : photosynthesis > Flashcards

Lecture 19 & 20 : photosynthesis Flashcards

1
Q

what is photosynth

A

A process that converts light energy into chemical energy. This chemical energy is used to convert atmospheric CO2 into carbohydrates

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2
Q

what is used instead of NADH in photosynth

A

NADPH

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3
Q

photosynth equation net

A

6CO2 + 6H2O + energy –>C6H12O6 + 6O2

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4
Q

what gets oxidised to produce the e- that go throught the e- chain

A

water (oxidised to O2)
this is the light dependent phase btw

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5
Q

what is the dark phase reaction

A

CO2 reduced to carbohydrate
can happen without light

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6
Q

whta does CO2 need to get reduced

A

ATP and NADPH

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7
Q

how is NADPH made

A

electrons from the H2O oxidation reduce NADP+ to NADPH

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8
Q

where in the chloroplast does phtosynth occur

A

thylakoid (membrane specifically cuz thats where all the machinery is)

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9
Q

what is ubiquinone equivalent in plants

A

plastoquinone

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10
Q

what type of cytochrome big membrane thing connects PSI and II in plants

A

cytochrome bf
links PSI and PSII

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11
Q

what is between cytochrome bf and PSI (equivalent to cytochrome c molecule)

A

plastocyanin

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12
Q

what passes e- to NADP reductase

A

ferrodoxin

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13
Q

where do e- move from and into through ATP synthase

A

thylakoid lumen to chloroplast stroma

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14
Q

what are the 2 pigments in phosotsystems

A

chlorophylls
carotenoids

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15
Q

what is final e- acceptor

A

NADP+

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16
Q

what wavelengths does PSI respond to

A

less than 690nm

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17
Q

name of pgments that first capture the light

A

antenna pigments

18
Q

what does the ‘special pair’ of chlorophyll molecules do in PSII

A

act as an energy trap
and e- can leave from here

19
Q

what ion in chlrophylls

A

Mg2+

20
Q

what is the one diff between chlorophyll a and b

A

a methyl group is an alcohol group

21
Q

what type of structure do chlorophyll have that makes it so e- can more readily absorb light energy

A

planar structure

22
Q

what nm is light not absorbed and gets reflected (hence green colour)

A

500-600nm

23
Q

when special pair loses its e- where does it replace it with

A

e- from H2O

24
Q

name of special pair in PSII

A

P680
P680* when it captures e-

25
Q

what is oxygen evolving centre

A

near the chlorophyll in PSII
e- from H2o captured here to go to oxidised P680

26
Q

what does oxygen evolving contain

A

1 Ca2+ and 4 Mn ions
which have h2o bound to it
and when e- snatched from this
given to chlorophyll

27
Q

what is in between oxygen evolving centre and chlorophyll

A

tyrosine
mediates e- trnasfer

28
Q

how many photons needed to generate one moleucle of o2

A

4
therefore 4e-

29
Q

how many protons transferred in total in the process of e- transfer to plastiquinone

A

4 from water released in thylakoid lumen
4 from stroma transferred to PQ to make PQH2

30
Q

how many protons does cyt bf transfer to thylakoid lumen and how

A

2
via Q cycle

31
Q

properties of plastocyanin

A

blue copper protein - this is what gets reduced, 1 at a time
soluble - exists in thyl memb

32
Q

Where does p700* recover its e- from

A

Plastocyanin

33
Q

what is in between psI and ferrodoxin

A

Iron sulphur clusters
Act as ijtermediate

34
Q

Where is ferrodoxin located

A

in stromal side

35
Q

What structure in NADP+ reductase allows the reduction of NADP+

A

FAD
Which can capture the e- and h+ one at a time and then pass the e- to nadp+ (2at a time)

36
Q

In what form are p680 and p700 good right reducing agents

A

when they are excited

37
Q

In what form are p680 and 700 good oxd agents

A

when they lose the e- and become +ve

38
Q

What are the subunits of atp synthase in atp synthase

A

CF0 and CF1
Same stalk and knob structure as in humans

39
Q

How many photons to make 3 atp

A

8
So 2.7 per atp

40
Q

What happens if no co2 or nadp+ is available

A

E- go from ferrodoxin back to cytochrome bf complex
Atp still synthesised, but no o2 or nadph made

Biochemistry (17 decks)

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