Photosynthesis - Light Dependent Reaction Flashcards
Component of photosystem + where is it
-Within thylakoid membrane in granum in chloroplast (light dependant reaction)
-Antenna complex + reaction centre
What happens in photosystem
-When light reach thylakoid membrane, electrons in antenna complex on first layer become excited
-Shifts and transfer energy to electron of the next pigment
-Carotenoid -> chlorophyll b -> chlorophyll a (reaction centre)
-electrons in chlorophyll A released into electrons acceptor
https://resource.download.wjec.co.uk/vtc/2020-21/el20-21_1-14/downloads/image_11.jpg
2 types of photosystem
Photosystem 1
-700nm of maximum absorption
-Absorb far red light
-Reduction of NADP co-enzyme
Photosystem 2
-680nm
-absorb red light
-photolysis (splitting water molecules)
Non-cyclic photophosphorylation 1-2
(Gaining ATP via light- non-continuous)
1)Light absorbed by PSII. Electron excited, move to higher energy level. Leave via reactive centre to e- acceptor in thylakoid membrane
2)Electron pass ETC on the way, lose energy for ETC to pump H+ to thylakoid lumen for ATP (maintain electrochemical gradient)
Non-cyclic photo phosphorylation
3)Electrons pass to PSI. Same process with 1.
4)NADP bind with electron + hydrogen in stroma to be reduced (maintain conc. gradient)
5)At PSII, water undergo photolysis, becomes electrons, hydrogen, oxygen (waste) in thylakoid, using sunlight
Non-cyclic photo phosphorylation- extra detail
Product - ATP + NADPH
If no water = shut down, PSII no electrons to send
Diagram of non-cyclic photo phosphorylation
https://resource.download.wjec.co.uk/vtc/2020-21/el20-21_1-14/downloads/image_12.png
Cyclic photo phosphorylation
1)PSI sends electron to 2 carriers using sunlight, to ETC for ATP then back to PSI to re use
PSI->()->()->ETC->PSI
Comparison of cyclic + non-cyclic
Non-cyclic
-PSI + PSII involved
-NADP final electron acceptor
-NADPH + ATP synthesised
-Non-continuous
Cyclic
-Only PSI
-PSI final electron acceptor
-ATP synthesised
-Continuous
