where does photosynthesis occur? which organelle and plant organ?
the chloroplasts, leaves
Overall equation for photosynthesis
6CO2 + 6H2O ⇒ C6H12O6 + 6O2
6 stages of the light dependent reaction
- Chlorophyll absorbs light and becomes photoionised (electrons are released).
- The photolysis of water produces the protons, electrons to replace those lost from chlorophyll, and oxygen.
- The electrons travel down the electron transport chain.
- Energy is released as electrons pass between carriers - this energy can be used to transport protons across the thylakoid membranes (into the thylakoids).
- Protons diffuse back into the stroma via ATP synthase channels, which are then able to catalyse the production of ATP: ADP + Pi ⇒ ATP + H2O. This is called chemiosmosis.
- The protons and electrons are taken up by NADP, which becomes reduced NADP and enters the light independent reaction.
What is produced in the light-dependent reaction?
ATP and reduced NADP
What does the production of ATP and reduced NADP in the light-dependent reaction conserve?
energy from the electrons released during photoionisation
Why is the photolysis of water needed?
to produce electrons which are used to replace those lost from chlorophyll.
To produce H+ for use in chemiosmosis.
4 stages of the light-independent reaction of photosynthesis
- CO2 reacts with ribulose bisphosphate (RuBP) to form 2 molecules of glycerate 3-phosphate (GP). This is catalysed by the enzyme rubisco.
- ATP and reduced NADP are used to reduce GP to triose phosphate.
- Some of the triose phosphate is used to regenerate RuBP in the Calvin cycle.
- Some of the TP is used to form useful organic substances such as glucose.
Where does the light independent reaction occur?
the stroma of chloroplasts
Where does the light dependent reaction occur?
on the thylakoid membranes
What is the purpose of photosynthesis?
plants use light energy from the sun to produce organic substances such as glucose.
Overview of the light independent reaction - what is used/ required?
Uses reduced NADP from the light dependent reaction to make a simple sugar. Hydrolysis of ATP from the light dependent reaction provides the additional energy required.
What is another name for the light-independent reaction of photosynthesis?
the Calvin cycle
Can the light-independent reaction take place in the absence of light? why/ why not?
The light independent reaction doesn’t need light directly, so theoretically should occur in the absence of light - however, it requires the ATP and reduced NADP from the light dependent stage (which requires light), so soon stops when light is removed.
limiting factors of photosynthesis
Temperature
Carbon dioxide concentration
Light intensity
What type of ATP production occurs in photosynthesis?
photophosphorylation
Which stage of photosynthesis produces ATP?
light-dependent
What type of organisms does photosynthesis occur in?
plants - photoautotrophs
How can the different pigments in leaves be investigated?
using chromatography
how does ATP synthase make ATP in respiration and photosynthesis?
by chemiosmosis
