7 - Photosynthesis Flashcards
How much carbon is fixed by photosynthesis per year?
10^13kg
What does the light reaction produce?
ATP and NADPH by photophosphorylation and ETC reduction.
Where does the O2 evolved during photosynthesis come from?
It is produced when water is oxidised though photolysis.
Give an overview of the dark reaction.
ATP and NADPH from the light reaction are used to reduce CO2 to produce triose phosphates.
Why is UV-Visible light absorbed in photosynthesis?
Longer wavelength rays are too low energy and higher energy rays are damaging or filtered out by the atmosphere.
What is the functional group in chlorophyll molecules?
A Mg ion complexed in a chlorin ring.
What is attached to the fourth ring in the chlorophyll chlorin?
A hydrophobic phytol side chain that allows membrane embedding.
Why is having different pigments with different absorption energies useful for an organism?
In crowded environments they can be used to form a niche for the organism, and absorb light not used by the others.
What is oxygenic photosynthesis?
The standard method of photosynthesis where water is oxidised to provide the electrons leading to oxygen evolution.
What is anoxygenic photosynthesis?
When a substance other than water is used as an electron source, often using double the amount in order to also reduce O2 to water.
What are some common anoxygenic photosynthesis substrates?
H2S
H2
Lactate
Give the standard equation for oxygenic photosynthesis.
CO2 + H2O → CH2O + O2
Give the standard equation for anoxygenic photosynthesis/
CO2 + 2(H2A) → CH2 + H2O + 2A-
What are the properties of purple bacteria?
Anaerobes capable of anoxygenic photosynthesis using a variety of reductants (though primary hydrogen sulphide).
Calvin Cycle used, unlike prokaryotes.
What are the properties of green sulphur bacteria?
Use sulphur products for anoxygenic photosynthesis.
No Calvin Cycle.
Live in low light environments.
What are the properties of green non-sulphur bacteria?
Diverse metabolism - variety of anoxygenic reductants used.
Hydroxyproprionate fixation.
What are the properties of helicobacteria?
They are known to be anoxygenic, but are otherwise mysterious.
What are the properties of cyanobacteria?
Oxygenic, unlike most prokaryotes.
Marine organisms with
What is the chloroplast an example of?
A plastid.
What is the aqueous phase inside the chloroplast called?
The stroma.
How are the internal membranes in the chloroplast arranged?
Into folded thylakoid membranes called lamellae. These are either unfolded (stromal) or appressed into tight grana (granal lamellae).
How did chloroplases evolve?
Through endosymbiosis of cyanobacteria.
How do chloroplasts replicate?
Independently of the cell using binary fission, after replicating and translating their genome using enzymes in the stroma.
What other forms can chloroplasts exist in?
They can often form from starch-filled amyloplasts which interconvert with proplastids, which in turn interconvert with chloroplasts via pregranal plastids.