Photosynthesis Flashcards
(13 cards)
Thylakoid
Where light reactions happen
Stroma
Liquid around thylakoids
Where Calvin cycle occurs
Stomata
Pores
Why is a leaf flat and large
High surface area to volume ration = increased rate of diffusion
Photosynthesis equation
6CO2 + 6H2O + light energy =
C6H12O6 + 6O2
Purpose of photosynthesis
Convert light energy into chemical energy (ATP and NADPH)
Light dependent reaction steps
- Light is absorbed into PSll, boosting 1 electron to a higher energy state
- Electron passes energy to nearby pigments as it “falls” energy states. Process continues until energy reaches p680, exciting an electron
- High energy e- is passed to primary e- acceptor and replaced with e- from splitting of H2O
- High energy e- travels down ETC, losing energy as it goes. This energy is used to pump H+ from the stroma into the thylakoid interior, against the concentration gradient, creating a high concentration of H+
- H+ flow through ATP synthase back into the stroma, driving ATP production (chemiosmosis)
- Electron arrives at PS1 at P700. Light is absorbed through pigments, e- is excited state at p700, transferred to acceptor molecule.
- Electrons travel down second ETC, where NADP+ becomes NADPH at NADP+ reductase
**ATP and NADPH carry chemical energy to Calvin cycle
Calvin Cycle Step 1: Carbon Fixation
- 5 Carbon RuBP + CO2 combines at enzyme Rubisco
- Splits into 2 molecules of 3-PGA
Calvin Cycle Step 2: Reduction
- 3-PGA accepts P from ATP, ATP——>ADP
And accepts H from NADPH, NADPH ——> NADP+
Resulting in G3P
Calvin Cycle Step 3: Regeneration
For 1 G3P to leave the cycle for glucose synthesis, 3CO2 must enter the cycle ——> 6G3P are made.
Of the 6, 1 is used to produce glucose, 5 are recycled to generate 3RuBP acceptors
How do C4 plants prevent photorespiration
By concentrating CO₂ in bundle-sheath cells, where the Calvin cycle occurs.
This creates a high CO₂ concentration.
How do CAM plants prevent photorespiration
At night, they open stomata to take in CO₂, which PEP carboxylase fixes into malate stored in vacuoles. During the day, stomata close to conserve water, and malate releases CO₂ for the Calvin cycle.
Photorespiration
In high, dry temperatures, where CO₂ is not available, Photorespiration is a process in plants where Rubisco binds oxygen instead of CO₂, leading to a loss of carbon and energy.
