Photosynthesis Flashcards
Describe the structure of chloroplast
Disc shaped
double membrane
Thylakoids - stacks of grana
Stroma - fluid filled matrix
where do the light dependent and light-independent reactions occur
Light dependent - Thylakoids of chloroplast
Light independent - stroma of chloroplast
What is the role of photosynthetic pigments
Absorb different wave lengths of light to maximise rate of photosynthesis
What are the two main groups of photosynthetic pigment
Primary Pigment - Found in photosystems
Accessory pigments - found in light-harvesting systems
Name the processes in the LDR
Photoionisation
ETC
Chemiosmosis
Non-cyclic only
- reduction of NADP
- Photolysis of water
Explain the role of light in photoionisation
Chlorophyll molecules absorb energy from photons of light
This excites 2 electrons, causing them to be released from the chlorophyll
What happens in the ETC
Electrons released from the chlorophyll move down a series of carrier proteins
Undergo a series of redox reactions which release energy
How does chemiosmosis produce ATP in the light-dependent stage
Some energy released form the ETC is coupled to active transport of H+ ions from stroma to thylakoid space
H+ ins move down concentration gradient via transmembrane channel protein ATP
ATP synthase catalyses ADP + Pi –> ATP
Describe non-cyclic photophosphorylation
Uses photosystems I and II
Excited electrons enter ETC to produce ATP
NADP acts as a final electron acceptor and is reduced
Water is photolysed to release electrons to replace lost ones
Produces ATP for Calvin cycle to produce biological compounds
Describe cyclic photophosphorylation
Only photosystem I
Excited electrons enter ETC to produce ATP then return directly to photosystem
Produces additional ATP to meet surplus energy demand
What happens in photolysis of water
Light energy splits molecules of water
2H2O –> 4H+ + 4e- + O2
Name the 3 stages in the light independent reaction
Carbon fixation
Reduction
Regeneration
What happens during carbon fixation
Reaction between CO2 and RuBP
Forms unstable 6C intermediate that breaks down
into 2 GP
What happens during reduction in the light independent stage
2 x GP reduced to 2 x TP
Requires 2x reduced NADP and 2x ATP
Forms 2x NADP and 2x ADP
Outline the roles of TP from the light independent stage
Leaves the cycle to produce monosaccharides, amnio acids etc
Involved on regeneration of RuBP
