light dependent stage Flashcards
what are the two stages of photosynthesis
light dependent
light independent
where does the light dependent stage
takes place in the thylakoid membrane and photosystems
During the light dependent stage, light energy is used to break down water to produce…
Hydrogen ions
electrons
oxygen
what is photolysis
when light energy is used to break down water to produce products of oxygen, protons and electrons
in photosystem I, What pigment is in the primary reaction centre
chlorophyll A, p700.
in photosystem II, What pigment is in the primary reaction centre
chlorophyll B, p680
what are some functions of water
- maintains plant turgidity
- produces oxygen and protons
- donates electrons to chlorophyll to replace those lost when light strikes chlorophyll
oxygen is produced by photolysis, where is it used
Used in aerobic respiration by plants or when light intensity is high, it is diffused out of stomata.
what is photophorylation
process of generation of atp from adp and an inorganic phosphate when light is present
what are the two types of phosphorylation and what are the differences
cyclic- involves only PSI, produces less atp than non cyclic
non cyclic- involves ps1 and ps2, produces atp, reduced NADP and O2
what is an electron carrier
it captures excited electrons from chlorophyll in the photosystems
it is a protein embedded in thylakoid membrane with an iron centre which can accept electrons and donate them to the next electron carrier protein
what photosystems does non cyclic phosphorylation use
PSII and PSI
what photosystem does cyclic phosphorylation use
PSI only
how is atp produced in the light dependent stage
some is released from electrons as they pass through the electron transport chain.
Also formed when protons pass through the special channels in the thylakoid membrane, the flow of protons produces atp
what causes excitation of electrons out of the chlorophyll in photosystems
when light strikes the photosystems, the light energy is channeled to the primary pigment in the centre of the reaction centre- chlorophyll.
This light energy excites a pair of electrons in the chlorophyll molecules
What is chemiosmosis
the transport of protons from the thylakoid space/ lumen to the stroma using special channels and ATP synthase in the thylakoid membrane
to produce ATP from ADP + Pi
what is photophosphorylation
Process of light energy producing ATP from ADP and inorganic phosphate
energy is used to pump protons across the thylakoid membrane into the thylakoid space. Where is this energy derived from.
The energy comes from when electrons pass electron carriers, some energy is released from the electrons.
This energy pumps protons into the space.
Summarise cyclic phosphorylation
light strikes PSI and chlorophyll at reaction centre gains energy, exciting its electrons.
Electrons pass to an electron transport chain
they then pass back to ps1.
producing a small amount of atp when electrons pass through the etc
Which produces LESS atp,
cyclic or non cyclic phosphorylation
Cyclic photophosphorlylation produces less atp than non cyclic
what is the final electron acceptor in Light dependent
NADP
what does NADP require to become reduced
electrons
hydrogen
in chemiosmosis, a proton gradient is produced where is the gradient produced
HIgh in thylakoid space,
low in stroma
what is atp synthase
an enzyme catalysing the synthesis of adp + pi into atp
what is reduction
gain of an electron
what is the equation for photolysis
2h20= 4h + 4e + o2
