Photosynthesis - Light Dependent Reaction Flashcards
What is the purpose of light dependent reactions?
Convert light energy into ATP and NADPH and release O2
Where do light dependent reactions occur?
In the thylakoid membranes of chloroplasts
What are grana?
Stacks of thylakoids
What is the stroma?
Fluid-filled matrix where the Calvin Cycle occurs
What is the thylakoid lumen?
The inner space of thylakoids where protons accumulate
Why are thylakoid membranes important?
They separate stroma and lumen to maintain a proton gradient
What pigment absorbs light in photosynthesis?
Chlorophyll
What does the magnesium atom do in chlorophyll?
It helps absorb light energy
What light does chlorophyll a absorb best?
Blue violet and red light
What happens when chlorophyll absorbs light?
Electrons become excited and reach high energy states
What is resonance energy transfer?
Transfer of energy between pigments until it reaches reaction center
What is the reaction center in PSII?
P680
What replaces lost electrons in P680?
Electrons from water split by the manganese cluster
What is the oxygen evolving complex?
Protein cluster that splits water into electrons protons and oxygen
What is the full equation of water splitting in PSII?
2H2O gives 4e minus 4H plus and O2
What happens to electrons after P680?
They move to pheophytin then plastoquinone A then B then mobile PQ
What is plastoquinone?
A lipid soluble carrier that becomes plastoquinol after accepting electrons and protons
What does plastoquinol deliver electrons to?
Cytochrome b6f complex
What is the Q cycle?
A process in cytochrome b6f that passes electrons to plastocyanin and pumps protons
What does cytochrome b6f contribute to?
Proton gradient in the thylakoid lumen
Where does PSI get its electrons?
From plastocyanin
What is the PSI reaction center?
P700
What metal ion is present in PSI reaction center?
Copper plus
Where are PSI electrons transferred after excitation?
To ferredoxin
