Lecture 19 & 20 : photosynthesis Flashcards
what is photosynth
A process that converts light energy into chemical energy. This chemical energy is used to convert atmospheric CO2 into carbohydrates
what is used instead of NADH in photosynth
NADPH
photosynth equation net
6CO2 + 6H2O + energy –>C6H12O6 + 6O2
what gets oxidised to produce the e- that go throught the e- chain
water (oxidised to O2)
this is the light dependent phase btw
what is the dark phase reaction
CO2 reduced to carbohydrate
can happen without light
whta does CO2 need to get reduced
ATP and NADPH
how is NADPH made
electrons from the H2O oxidation reduce NADP+ to NADPH
where in the chloroplast does phtosynth occur
thylakoid (membrane specifically cuz thats where all the machinery is)
what is ubiquinone equivalent in plants
plastoquinone
what type of cytochrome big membrane thing connects PSI and II in plants
cytochrome bf
links PSI and PSII
what is between cytochrome bf and PSI (equivalent to cytochrome c molecule)
plastocyanin
what passes e- to NADP reductase
ferrodoxin
where do e- move from and into through ATP synthase
thylakoid lumen to chloroplast stroma
what are the 2 pigments in phosotsystems
chlorophylls
carotenoids
what is final e- acceptor
NADP+
what wavelengths does PSI respond to
less than 690nm
name of pgments that first capture the light
antenna pigments
what does the ‘special pair’ of chlorophyll molecules do in PSII
act as an energy trap
and e- can leave from here
what ion in chlrophylls
Mg2+
what is the one diff between chlorophyll a and b
a methyl group is an alcohol group
what type of structure do chlorophyll have that makes it so e- can more readily absorb light energy
planar structure
what nm is light not absorbed and gets reflected (hence green colour)
500-600nm
when special pair loses its e- where does it replace it with
e- from H2O
name of special pair in PSII
P680
P680* when it captures e-
what is oxygen evolving centre
near the chlorophyll in PSII
e- from H2o captured here to go to oxidised P680
what does oxygen evolving contain
1 Ca2+ and 4 Mn ions
which have h2o bound to it
and when e- snatched from this
given to chlorophyll
what is in between oxygen evolving centre and chlorophyll
tyrosine
mediates e- trnasfer
how many photons needed to generate one moleucle of o2
4
therefore 4e-
how many protons transferred in total in the process of e- transfer to plastiquinone
4 from water released in thylakoid lumen
4 from stroma transferred to PQ to make PQH2
how many protons does cyt bf transfer to thylakoid lumen and how
2
via Q cycle
properties of plastocyanin
blue copper protein - this is what gets reduced, 1 at a time
soluble - exists in thyl memb
Where does p700* recover its e- from
Plastocyanin
what is in between psI and ferrodoxin
Iron sulphur clusters
Act as ijtermediate
Where is ferrodoxin located
in stromal side
What structure in NADP+ reductase allows the reduction of NADP+
FAD
Which can capture the e- and h+ one at a time and then pass the e- to nadp+ (2at a time)
In what form are p680 and p700 good right reducing agents
when they are excited
In what form are p680 and 700 good oxd agents
when they lose the e- and become +ve
What are the subunits of atp synthase in atp synthase
CF0 and CF1
Same stalk and knob structure as in humans
How many photons to make 3 atp
8
So 2.7 per atp
What happens if no co2 or nadp+ is available
E- go from ferrodoxin back to cytochrome bf complex
Atp still synthesised, but no o2 or nadph made
