Light Reactions Flashcards
what are chloroplasts for?
genes encode for proteins in photosynthesis
how does chloroplast rise from?
pre-existing chloroplasts thru fission
how many membranes does chloroplasts have?
3
what are the 3 membranes of chloroplasts?
- outer membrane
- inner membrane
- thylakoid membrane
What are the features of outer membrane?
- relatively permeable
- contain porins
What are the features of inner membrane?
- highly permeable
- require transporters
What are the features of thylakoid membrane?
- site of light reactions
- contain intergral proteins
- contain pigments
what are the two different functional units of plant chloroplasts in light energy conversion into chemical energy?
photosystems I (P700)
photosystems II (P680)
Where are the photosystems located?
thylakoid membrane
what are the feature of photosystem II?
absorbs @ shorter and more energetic wavelength
What are is the order of photosystem
start with photosystem II then photosystem I
What is the structure of photosynthetic apparatus , what are the four protein complexes?
- Photosystem II
- Cytochrome b6f complex
- photosystem I
- ATP synthase
What do the four protein complexes have?
vectorial arrangement
What are the two mobile carriers?
- plastoquinone
- plastocyanin
what are stroma lamellae?
unstacked
What are grana lamellae?
stacked
What are the structure of PSII photosystem?
stacked regions
What are the PSI photosystem/ETC Proteins/ ATP Synthase structure?
unstacked regions
What are cyt b6f structure?
even distributed
Where are is the ATP synthase?
unstacked stroma lamellae
what is the process of production of ATP?
ATP produced needs to be released into stroma to be available for calvin cycle rxns
what are antenna complexes?
light-harvesting complexes or LHC
What does antenna complexes contain?
chlorophyll a, chlorophyll b and carotenoids
What are the mechanism involved in antenna complexes?
resonance energy transfer (vibrational)
how are energy passes of antennae complexes?
down energy gradient, higher energy (shorter wavelength) to lower energy (longer wavelength) thru resonance up to Reaction Center
What happens when reached energy Reaction Center?
chlorophyll molecule of either PSII or PSI
Chl molecule absorbs light energy and becomes excited Chl*
what are the pigments associated with light-harvesting antenna complextes?
LHC II
LHC I
what happens when pigments are near the reaction centre?
longer wavelength maxima
red shift in absorption max
what does it give to reaction centre?
directionality/irreversibility to energy transfer
how does light excited reaction centre chlorophyll molecule?
- directly
- thru resonance ( energy transfer from antenna molecules)
what is the strongest oxidizing agent or oxidant (e- acceptor) in biological system?
excited PSII reaction centre chlorophyll (P680+)
how is light energy converted to chemical energy?
thru the light-dependent reactions
what are the types of ractions?
- Non-cyclic Electron Flow
- Cyclic Electron Flow
What does the non-cyclic electron flow use?
PSII and PSI
What is the non-cyclic electron flow?
thru linear electron flow pathway or the Z-scheme of photosynthesis
What does the cyclic electron flow use?
PSI
What is the cyclic electron flow?
thru non-linear electron flow pathway
what does the PSII absorbs in the non-cyclic electron flow?
red light
What does the PSI absorbs in the non-cyclic electron flow?
in far-red light
what happens in the non-cyclic electron flow?
excited electron transferred to primary electron acceptor, convert from light to chemical energy
what does the light absorption and electron transport generate?
ATP and NADPH thru Z-scheme
what is the sequenece?
- photon absorption in PSII (P680) or PSI (P700)
- oxidation of water to generate electrons
- electron transfer to cytochrome b6f or from cytochrome b6f
- Electron transport to ferredoxin or to NADPH reductase
- photophosphorylation
what happens in the photon absorption in PSII and PSI reaction center
Absorb light lead to
1. splitting H2O
2. generating H+ gradient
proteins D1 and D2 bind P680 reaction center chlorophyll and ETC
What is PSII have?
20 polypeptides
within thylakoid membrane
What happens when excited electron from P680 do?
accepted by pheophytin
what is the most stable in water moelcule?
splitting water - endergonic reaction
what happens when P680* loses it’s excited electron to Pheophytin?
oxidized to P680+
what is the most powerful oxidizing agent?
P680+
what can P680+ do?
photolysis of water - pulling electrons from H2O molecule
what are features of plastoquinone?
hydrophobic
mobile within membrane
what are the features of plastocyanin?
small, water-soluble
on lumen side
how does