Photosynthesis (complete) Flashcards
Describe The Photolysis of water during the Light-dependant reaction of photosynthesis.
The Photolysis of Water -
- light energy is absorbed by the chlorophyll, splitting water into hydrogen ions, electrons and oxygen molecules.
- the hydrogen ions are picked up by NADP to form NADPH for the light-independent reaction.
- the electrons replace those lost during the photoionisation of chlorophyll.
- the oxygen is either used for respiration, or diffuses out of the leaf during the stomata.
Describe The Photoionisation of Chlorophyll during the light-dependant reaction of photosynthesis.
- light energy from the sun is absorbed by the chlorophyll, resulting in the electrons present in the chlorophyll gaining energy, so raising them up an energy level, causing them to leave the chlorophyll - photoionisation.
Describe the process of Chemiosmosis during the light-dependant reaction.
- the electrons that gained energy and were released from the chlorophyll move along a series of electron carrier proteins in the thylakoid membrane of the mitochondria.
- as the electrons move along the proteins, they release energy, so losing energy, and some of that energy is used to pump the protons formed during the photolysis of water from the stroma, across a proton pump and into the thylakoid lumen.
- their results in an electrochemical gradient being built up, which allows the protons to move again, by facilitated diffusion,, back down their concentration gradient, through ATP synthase back to the stroma.
- as the proton attaches to and moves through then enzyme, with which the shape change of the enzyme catalyses the phosphorylation of ADP into ATP.
- reduced NADP is formed when the protons are back on the stroma side, and the NADP picks up the electrons at the end of the electron transport chain, as well as the protons once they’ve passed through the ATP synthase, which reduces the NADP forming NADPH.
Describe the process of the Calvin cycle in the light-independent reaction.
- RuBP reacts with CO2 (catalysed by rubisco) to form 2 molecules of GP.
- GP is then formed into TP using the energy from the deformation of ATP into ADP + Pi
finish
Name the limiting factors of photosynthesis and briefly describe.
- Co2 concentration - lower concentration = reduced rate; important reactant in calvin cycle.
- Light intensity - lower intensity = reduced rate; light required during light-dependant reaction (photolysis/photoionisation).
- Temperature - lower temperature = reduced rate/higher temperature = no photosynthesis; enzymes involved in chemiosmosis and calvin cycle.
Name the co-enzyme involved in photosynthesis and it’s functions.
NADP -
- combines with protons from the photolysis of water to be used during the LIR.
- combines with protons from the end of the electron transport chain during chemiosmosis.
- donates protons to calvin cycle (from photolysis of water) to reduce GP molecules within the cycle to TP
Give the equation for photolysis of water.
2H2O —> O2 + 4e- + 4H+
Where does the:
- Light dependant reaction occur?
- Light independent reaction occur?
- LDR - thylakoid membranes and spaces
- LIR - stroma
How can the limiting factors of photosynthesis be controlled?
- using artificial lighting to maximise light energy.
- heat greenhouses by burning fuel to increase temperature and release CO2.
What are some disadvantages of controlling limiting factors of photosynthesis?
- Cost - need to still make a profit/be cost effective.
- Difficult to store lots of fuel to burn to allow for released CO2 to enter greenhouse.
Give the equation for photosynthesis.
Carbon dioxide + Water —> Glucose + Oxygen.
Name the overall products of:
- The Light dependant reaction.
- The Light independent reaction.
- LDR - produces NADPH and ATP.
- LIR - produces useful organic substances.
Describe the light compensation point.
- where the light intensity is at a point where the rate of photosynthesis if equal to the rate of respiration.
