Ps Flashcards
Where do the light dependent and light independent reactions occur in plants?
LDR: thylakoids
LIR: stroma
What process takes place to start the ETC?
Photoionisation:
- light is absorbed by chlorophyll
- light excites the e-s in chlorophyll (raisesthem to a higher Elevel) so they’re released from the molecule.
Describe part I of the LDR.
ETC:
Electrons released from the chlorophyll move down a series of carrier proteins embedded in the thylakoid membrane and undergo a series of redox reactions whic release energy.
How does the ETC affect chemiosmosis?
It establishes a concerntration gradient for chemiosmosis.
Some E released from the ETC is coupled to the active transport of protons from the stroma to the thylakoid space.
Describe part II of the LDR.
Protons move from the thylakoid space into the stroma,down thir concerntration gradient, via ATP synthase.
The movement down the conc. gradient catalyses the reaction:
ADP + Pi -> ATP
State the roles of AP and reduced NADP in the LIR.
ATP: reduction of GP to TP and provides phospate group to convert RuP into RuBP.
Reduced NADP: coenzyme transports electrons needed forreduction of GP to TP.
What is the purpose of the LDR?
to capture light energy to:
- make ATP
- photolysis - to split water into protons and hydroxide ions.
(remeber photosynthsis is the making of glucose and oxyge from CO2 and water)
- this is where the water comes from and wy O2 is produced from the LDR.
Diagram of how the LDR and LIR interact.
Where do the protons and electrons used to reduce NADP come from?
Protons: photolysis of water
Electrons: NADP acts as the final electron acceptor in the ETC.
Three main stages of the Calvin cycle.
- Carbon fixation
- reduction
- Regeneration
Outline the sequence of events in the light dependent reaction (Calvin cycle).
Describe the Calvin cycle.
Carbon fixation
- Reacion between RuBP (ribulose isphosphat) and CO2 catalysed by rubisco.
- forms unstable 6C intermediate that breaks down into 2x glycerate-3-phosphate
Reduction:
- 2x G3P are reduced to 2xTP
- requires 2x reduced NADP and 2xATP froms 2xNADP and 2xATP
Regeneration
- After 1C leaves the cycle, the 5C compound RuP forms.
- RuBP is regenerated from RuP using 1xATP
- forms 1xADP
How are the products of the LDR used in the LIR?
ATP and reduced NADP from the LDR supply the energy and hydrogen needed to make simple sugars from CO2.
How and where is reduced NADP produced in the LDR?
- NADP + 2H+ +2e- -> reduced NADP
- catalysed by dehydrogenase enzymes
- stroma of chloroplasts
What happens to the products of the photolysis of water?
Protons: move out of thylakoid space via ATP synthase to reduce the coenzyme NADP.
Electrons: replace electrons lost from chlorophyll
Oxygen: used for respiration or diffuses out of the leaf as a waste gas.
