Photosynthesis Flashcards
Give the equation for photosynthesis.
6CO2 + 6H2O -> C6H12O6 + 6O2
What is the first stage of photosynthesis called?
The light dependent reaction.
Where does the 1st stage of photosynthesis take place?
The thylakoid membrane
Light dependent reaction leads to the production of which molecule and the occurrence of what process?
ATP
Photolysis of water
Light energy is absorbed by what pigment in the chloroplast?
Chlorophyll
Absorption of light into the chloroplast does what to electrons?
Excites the electrons into a higher energy level
Name the process where electrons in the LDR are released as a result of excitation.
Photoionisation
After electrons have been released in the LDR, where do they travel to?
An electron acceptor at the start of the ETC.
Attachment of electrons to an electron carrier does what to the electron carrier in the LDR?
The electron carrier becomes reduced.
A series of what type of reactions pass electrons down the ETC during the LDR?
Redox
Why do electrons lose energy as they are passed down the ETC in the LDR?
Each electron carrier is at a slightly lower energy level, so electrons lose energy
Where does energy come from to be used for ATP production in the LDR?
What is the name for this type of ATP production?
Energy lost as electrons are passed down the chain is used to provide energy for ATP production.
This is called photophosphorylation
What does chemiosmotic theory explain?
Mechanism of ATP production
In chemiosmosis, how do H+ get into the thylakoid from the stroma?
Name the pumps used
Active transport, using proton pumps.
Why does the concentration of H+ ions increase in the thylakoid during chemiosmosis?
Where in the chloroplast will have high/low concentration of H+?
Photolysis of water produces H+. This means that there is a high concentration of H+ in the thylakoid and a low concentration in the stroma.
Energy for active transport of H+ in chemiosmosis comes from where?
Photolysis of water, when electrons are released.
In chemiosmosis, how do protons cross the thylakoid membrane?
Through ATP synthase channels
How does movement of H+ through ATP synthase channels lead to the catalysing of ADP + Pi?
Movement of H+ leads to the protein changing shape, therefore catalysing the reaction.
For chlorophyll to be able to continue absorbing light, what must happen?
Electrons must be replaced
Where do replacement electrons for the chlorophyll come from after some electrons have left the chlorophyll to travel down the ETC?
Replacement electrons come from when water is photolysed (split using light).
Give an equation for the photolysis of water.
2H2O -> 4H+ +4e- + O2
Protons generated in photolysis pass out of which component of the chloroplast through what type of channels?
Protons leave the thylakoid through ATP synthase channels.
Protons that have left the thylakoid during photolysis are picked up by which coenzyme?
NADP, which becomes reduced NADP
Reduced NADP acts as a source of what type of energy for the plant?
Chemical energy
Reduced NADP enters the light independent reaction after photolysis, carrying what?
Electrons that have come from the original chlorophyll molecule.
What is another name for the light independent reaction?
The Calvin Cycle
The light independent stage occurs in which part of the chloroplast?
The stroma.
The light independent stage uses which 2 molecules from the light dependent stage?
Reduced NADP and ATP
What is the first stage of the light independent reaction called?
Carbon fixation
Describe the structure of ribulose biphosphate.
5C with 2 phosphate groups attached
How many CO2 molecules are inputted into the Calvin cycle?
3
Rubisco catalyses the reaction between which molecules?
Ribulose biphosphate and CO2
What is rubisco short for?
Ribulose bisphosphate carboxylase
How many carbons are in the molecule produced after the reaction between ribulose biphosphate + CO2
6
Why does the product formed from ribulose biphosphate + CO2 immediately split into 2?
What is the product called?
The 6C biphosphate molecule is unstable.
Therefore, it splits into 2 glycerate-3-phosphate molecules.
What is the second stage of the light independent reaction called?
Reduction
In the LIR, glycerate-3-phosphate reduces into what molecule?
Which molecules assist this?
Triose phosphate.
This is done with the help of reduced NADP, which becomes oxidised, and ATP which releases it’s phosphate.
How many ATP involved in the reduction stage?
How many NADPH?
6ATP
6NADPH
What is the 3rd stage of the LIR called?
Regeneration
How many turns of the Calvin cycle are needed to produce 1 glucose molecule?
6
What happens to the triose phosphate in the regeneration stage of the Calvin cycle?
It’s recycled
How much ATP is used in the regeneration stage of the Calvin cycle?
3
How is ribulose biphosphate regenerated at the end of the Calvin cycle?
ATP turns remaining triose phosphate molecules into ribulose biphosphate.
Thylakoid membranes provide a large SA for the attachment of what 3 things?
Chlorophyll molecules
Electron carriers
Enzymes
Name 2 adaptations do the grana membranes have for photosynthesis.
Many ATP synthase channels
Selectively permeable
Why do chloroplasts contain DNA and ribosomes?
To quickly synthesise proteins required for photosynthesis
What does the stroma contain that is needed for the light independent reaction?
Enzymes
What are the benefits of the stromal fluid surrounding the grana for the light independent reaction?
Short diffusion pathway for diffusion of products into the stroma.
