AQA A Level Biology - Photosynthesis
Questions And Answers
What are the two stages of photosynthesis called>
The Light Dependent reaction
The Light Independent reaction (The calvin cycle)
What is the purpose of photosynthesis?
To energy from light is used to make glucose
What is the general equation for photosynthesis ?
6H2O + 6CO2 + energy --> C6H12O6 + 6O2
What are the x stages of the light dependent reaction ?
1. Photoionisation of PSII
2. Photolysis of water
3. Photoionisation of PSI
4. Active transport of H+ ions
5. Oxidative phosphorylation
6. Reducing NADP
Describe what happens during photoionisation of PSII
Chlorophyll absorbs light
Electrons excited and move to higher energy level
Electrons move down electron transport chain to PSI
Describe what happens during photolysis of water
Light energy splits water molecules into H+, e- and oxygen
The electrons replace those lost from PSII during photoionisation
Explain how H+ ions are moved across the thylakoid membrane
The excited electrons from photoionisation lose energy as they move down the
electron transport chain
The energy is used to actively transport H+ into the chloroplast
Explain how H+ are involved in the synthesis of ATP in chloroplasts
H+ move down their concentration gradient into the stroma
This is via ATP synthase in the thylakoid membrane
The energy synthesises ATP from ADP and Pi
Explain why the photoionisation of PSI is important
, The excited eletrons are transferred to NADP with H+ to form reduced NADP
This is needed for the light-independent reaction
What is chemiosmosis ?
Electrons move down the electron transport chain and creating a proton gradient
This drived ATP synthesis
Which molecules from the light-dependent reaction are needed in the light-
independent reaction?
ATP
reduced NADP
Where does the light dependent reaction take place?
(acrodd) thylakoid membranes of chloroplasts
Where does the light-independent reaction take place?
Stroma of chloroplasts
What are the 3 stages of the light-independent reaction?
1. Formation of glycerate 3-phosphate
2. Formation of triose phosphate
3. Regeneration of ribulose bisphosphate
Explain how glycerate 3-phosphate (GP) is formed
Ribulose bisphosphate (RuBP) combines with CO2
Forms unstable 6 carbon compound which breaks down to give 2 molecules of
glycerate 3-phosphate
Catalysed by Rubisco
How does CO2 enter the stroma from the atmosphere?
Diffusion through the stomata
Difussion into the stroma
Which enzyme catalyses the reaction of CO2 with ribulose bisphosphate
(RuBP) ?
Rubisco
How many molecules of glycerate 3-phosphate (GP) are produced from 1
molecule of CO2 and 1 molecule of ribulose bisphosphate (RuBP) ?
2
How many carbon atoms are in ribulose bisphosphate ?
5
How many carbon atoms are in glycerate 3-phosphate (GP) ?
Questions And Answers
What are the two stages of photosynthesis called>
The Light Dependent reaction
The Light Independent reaction (The calvin cycle)
What is the purpose of photosynthesis?
To energy from light is used to make glucose
What is the general equation for photosynthesis ?
6H2O + 6CO2 + energy --> C6H12O6 + 6O2
What are the x stages of the light dependent reaction ?
1. Photoionisation of PSII
2. Photolysis of water
3. Photoionisation of PSI
4. Active transport of H+ ions
5. Oxidative phosphorylation
6. Reducing NADP
Describe what happens during photoionisation of PSII
Chlorophyll absorbs light
Electrons excited and move to higher energy level
Electrons move down electron transport chain to PSI
Describe what happens during photolysis of water
Light energy splits water molecules into H+, e- and oxygen
The electrons replace those lost from PSII during photoionisation
Explain how H+ ions are moved across the thylakoid membrane
The excited electrons from photoionisation lose energy as they move down the
electron transport chain
The energy is used to actively transport H+ into the chloroplast
Explain how H+ are involved in the synthesis of ATP in chloroplasts
H+ move down their concentration gradient into the stroma
This is via ATP synthase in the thylakoid membrane
The energy synthesises ATP from ADP and Pi
Explain why the photoionisation of PSI is important
, The excited eletrons are transferred to NADP with H+ to form reduced NADP
This is needed for the light-independent reaction
What is chemiosmosis ?
Electrons move down the electron transport chain and creating a proton gradient
This drived ATP synthesis
Which molecules from the light-dependent reaction are needed in the light-
independent reaction?
ATP
reduced NADP
Where does the light dependent reaction take place?
(acrodd) thylakoid membranes of chloroplasts
Where does the light-independent reaction take place?
Stroma of chloroplasts
What are the 3 stages of the light-independent reaction?
1. Formation of glycerate 3-phosphate
2. Formation of triose phosphate
3. Regeneration of ribulose bisphosphate
Explain how glycerate 3-phosphate (GP) is formed
Ribulose bisphosphate (RuBP) combines with CO2
Forms unstable 6 carbon compound which breaks down to give 2 molecules of
glycerate 3-phosphate
Catalysed by Rubisco
How does CO2 enter the stroma from the atmosphere?
Diffusion through the stomata
Difussion into the stroma
Which enzyme catalyses the reaction of CO2 with ribulose bisphosphate
(RuBP) ?
Rubisco
How many molecules of glycerate 3-phosphate (GP) are produced from 1
molecule of CO2 and 1 molecule of ribulose bisphosphate (RuBP) ?
2
How many carbon atoms are in ribulose bisphosphate ?
5
How many carbon atoms are in glycerate 3-phosphate (GP) ?
