Photosynthesis (Johnson) Flashcards
How many power does the sun deliver per year?
100 000 TW
How much power do humans use annually?
15 TW
The energy in all of Earth’s oil resources is provided by the sun in how long?
1.5days
How much power does chlorophyll capture annually?
~100TV
What are humankind’s biggest problems?
Food/Energy/Less CO2
Name the four types of photosynthetic organism
Eukaryotic oxygenic photosynthesis Prokaryotic oxygenic photosynthesis Archael photosynthesis Prokaryotic anoyxgenic photosynthesis
Name some photosynthetic organisms found in each type
EOP
Plants, Mosses, Green/Red/Brown Algae
POP
Cyanobacteria (-)
AP
Halobacteria
PAP
Purple Bacteria (-), Purple Sulphur Bacteria (-), Green Sulphur Bacteria (-), Green Gilding Bacteria (-), Heliobacteria (+)
Where does photosynthetic electron transfer take place?
The thylakoid membrane
Where does CO2 fixation take place?
In the stroma.
What is plastoquinone and where is it found?
A lipid soluble electron carrier in the PET chain.
What is cytochrome b6-f complex equivalent to?
The respiration Q cycle
How many light-driven reactions occur, and where?
2 at both Photosystem I and II
What do antenna complexes do?
Absorb photos and pass ‘excitation energy’ to the reaction centre.
What is special about the reaction centre chlorophylls?
They are redox active
What are the main structuraly components of the chlorophyll molecule?
- A tetrapyrolle ring that coordinates a Mg2+ ion
- A hydrophobic pytyl tail
- A conjugated pi electron sstem at the ring that is responsible for photon absorption
What wavelength photon promotes an S0 electron to S1?
656nm
S0 and S1 are electronic states of the molecule. Chlorophyll is a complex molecule (large pi electron system): what does this mean, with regards to its electronic states?
There are multiple vibrational sub-levels for each electronic state.
How long does light absorption take?
1fs
Why can chlorophyll light absorption be plotted as a gaussian distribution?
Not every transition has the same probability of being populated as others.
What is the name for the process where a promoted electron and falls to a lower sub-level?
Vibrational relaxation
What is the name for the process where an electron falls to the next lowest electronic state?
Internal conversion
Vibrational relaxation and internal conversion in S2-S1 occur on what timescale?
Ultrafast (picosecond)
Why does internal conversion from S1 –> S2 occur on the nanosecond timescale?
The electron is closer to the nucleus - the excited state is more stable.
What de-excitation channel can compete with S1–>S0 internal conversion?
Fluorescence?
From which vibrational sub-level does fluorescence only occur?
The lower sub-level.
