5.1 (11) - Photosynthesis Flashcards
What is the balanced symbol equation for photosynthesis?
6CO2 + 6H2O > C6H12O6 +6O2
Which coenzyme does photosynthesis use?
What does it do?
NADP
It carries electrons and hydrogen to and from molecules
Where does the LDR take place?
Thylakoid membrane of grana in chloroplasts
What are the 4 main stages of the LDR?
- Photoionisation of chlorophyll
- Electrons pass down the ETC
- Photolysis of water
- Production of ATP
Describe the photoionisation of chlorophyll in the LDR
1) Chlorophyll absorbs light energy
2) Chlorophyll’s electrons gain energy and become
excited
3) Some electrons are emitted from the chlorophyll
Describe how electrons pass down the ETC, following photoionisation
1) Electrons emitted from chlorophyll pass down the ETC through electron carriers
2) They lose energy as they pass down the ETC
3) These will be accepted by NADP later
Describe the photolysis of water in the LDR
1) Light energy breaks the bonds between the oxygen and hydrogen of 2 water molecules
2) From 2 water molecules:
- 4 protons (accumulate in the thylakoid space)
- 4 electrons (replace those lost from chlorophyll)
- 1 oxygen molecule (waste product)
are released
Describe how protons are used to synthesise ATP
1) Protons are actively transported across from the stroma to the thylakoid space, using the energy lost from electrons passing down the ETC
2) The protons diffuse across the thylakoid membrane through ATP synthase
3) ATP synthase undergoes a conformational change by spinning
4) The kinetic energy from ATP synthase’s conformational change allows ADP to couple with Pi
5) The diffusing protons enter the stroma and are accepted by NADP
6) NADP also accepts electrons from the ETC, forming reduced NADP
Describe what happens during the LDR
1) Chlorophyll absorbs light energy
2) Chlorophyll’s electrons gain energy and become
excited
3) Some electrons are emitted from the chlorophyll
4) Emitted electrons pass down the ETC through electron carriers
5) The electrons lose energy as they pass down the ETC
6) Light strikes 2 water molecules, breaking bonds between their hydrogens and oxygens
7) The light splits it into 4 protons (accumulate in thylakoid space), 4 electrons (replace those lost from chlorophyll) and a water molecule (waste product)
8) Protons are actively transported across from the stroma to the thylakoid space, using the energy lost from electrons passing down the ETC
9) The protons diffuse across the thylakoid membrane through ATP synthase
10) ATP synthase undergoes a conformational change by spinning
11) The kinetic energy from ATP synthase’s conformational change allows ADP to couple with Pi
12) The diffusing protons enter the stroma and are accepted by NADP
13) NADP also accepts electrons from the ETC, forming reduced NADP
Where does the LIR take place?
Stroma of chloroplasts
What are the 3 main stages of the Calvin cycle?
- Carbon fixation
- Reduction of G3P
- Regeneration of RuBP
Describe what happens during carbon fixation in the Calvin cycle
1) CO2 reacts with RuBP. RuBisCO catalyses this reaction
2) These molecules combine to make a 6 carbon molecule
3) CO2 makes this unstable, so it splits into 2 molecules of G3P
Describe what happens during the reduction of G3P
1) Each G3P molecule is reduced by NADPH (NADPH is oxidised)
2) Reduced G3P becomes TP
3) ATP provides energy for this to happen - it is hydrolysed into ADP + Pi
Describe what happens during the regeneration of RuBP
1) Most of the TP is regenerated into RuBP - ATP provides the energy for this (hydrolysed into ADP + Pi)
2) Some of the TP will be used to synthesise useful organic substances (eg. glucose)
Describe what happens during the LIR
1) CO2 reacts with RuBP. RuBisCO catalyses this reaction
2) These molecules combine to make a 6 carbon molecule
3) CO2 makes this unstable, so it splits into 2 molecules of G3P
4) Each G3P molecule is reduced by NADPH (NADPH is oxidised)
5) Reduced G3P becomes TP
6) ATP provides energy for this to happen - it is hydrolysed into ADP + Pi
7) Most of the TP is regenerated into RuBP - ATP provides the energy for this (hydrolysed into ADP + Pi)
8) Some of the TP will be used to synthesise useful organic substances (eg. glucose)
