Light Dependent Reaction Flashcards
- requires sunlight
- occurs in thylakoid membrane
- involves two photosystems and an electron transport chain
light-dependent reaction
where does LDR occur?
thylakoid membrane
Large complexes of proteins and pigments (light absorbing molecules) that are optimized to harvest light.
photosystem
Reaction-center complex and Light- harvesting complex
photosystem
- Special pair of chl a molecules
- Primary electron acceptor
Reaction-center complex
- With various pigment molecules (~300-400)
Light- harvesting complex
goal of photosystem
create ATP and NADPH by energizing the two photosystems
PS1 special pair of chl a molecules
P700
PS2 special pair of chl a molecules
P680
sequence of LDR
light absorption in PS2, atp synthesis, light absorption in PS1, nadph formation
movement of energy from one pigment to another until it reachers the special pair of chlorophyll a molecule
resonance energy transfer
primary electron acceptor of PS2
pheophytin
One of the molecule’s electrons is elevated to an orbital where it has more potential energy, which
makes it _____.
excited
The electron will be passed on
through the first leg of the photosynthetic electron
transport chain in a series of
_______
redox reaction
to fill the donated electron of PS 2
photolysis
where does photolysis happen?
thylakoid lumen
photolysis
An enzyme catalyzes water to split into:
* 2 electrons
* 2 Hydrogen ions (H+)
* 1 oxygen atom
in photolysis, hydrogen ions
stay in the thlyakoid lumen
in photolysis, oxygen atom
Forms O2 and exits via stomata
From the primary electron acceptor, the electron is now transferred to PS I via the
electron transport chain
electron transport chain
o Cytochrome complex (Cyt)
o Plastoquinone (Pq)
o Protein- plastocyanin (Pc)
ETC releases
free energy
PS1 primary electron acceptor
A0
PS1
Electrons are passed in a series of redox reactions down to the ETC through the protein
ferredoxin (Fd)
_______ catalyzes the transfer of electrons from Fd to NADP+
NADP+ reductase
_____ electrons are needed to reduce NADP+ to NADPH
two
The movement of hydrogen ions down their electrochemical gradient through the transmembrane enzyme ATP synthase.
chemiosmosis
Electrons loop back to the first part of the electron transport chain, repeatedly cycling through PSI instead of ending up in NADPH.
Cyclic Photophosphorylation
Cyclic Photophosphorylation
The electrons cycle back from ____ to the ______, then via a _____ to a
P700 chlorophyll in the PS I
reaction-center complex.
ferredoxin (Fd), cytochrome complex, plastocyanin molecule (Pc)
No release of oxygen or production of NADPH but generates ATP
Cyclic Photophosphorylation
o Single photosystems such as purple and green sulfur bacteria
o Mutations
o when too little NADP is available to accept electrons
o High ATP needs
o For photoprotection
Cyclic Photophosphorylation
