L12 Photosynthesis Flashcards
What is photosynthesis?
The process of converting light into chemical bond energy
Sunlight energy, CO2 and H2O go into the plant, carbohydrates are formed, O2 is released
O2 is the key to unlocking the newly stored energy
Thermodynamics: Gibbs free energy
deltaG = “Gibbs free energy” = a measure of chemical energy for reactions
deltaG(W) = change in free energy at 1atm, 25C pH7
production of glucose:
6CO2 + 6H2O –> C6H12O6 + 6O2
deltaG = +ve = reaction requires energy
C6H12O6 + 6O2 –> 6CO2 + 6H2O
delataG = -ve = reaction releases energy
Oxidation vs Reduction
Oxidation: during the light phase of photosynthesis, atoms lose electrons
Reduction (synthesis): during the dark phase (no light required), can happen in both daylight and darkness, atoms receive electrons
***refer to L12 slide 14 for example of cancelling electrons and slide 16 for a graph of oxidation vs synthesis
How does fall effect photosynthetic pathways?
ratio of photosystem II to photosystem I decreases (less photosystem II)
photosystem II responsible for chlorophyll (green)
photosystem I responsible for carotene (yellow) and anthocyanins (red)
that’s why leaves change colours :0
What are some climate change impacts on photosynthesis?
Climate change generally increases photosynthesis:
- more Co2
- warmer temps
Photoperiod (daylight hours):
affects relative participation of photosystems I and II
Temperature:
- warmer temp (or related cold temp) in fall
- delayed fall foliage colours