Lecture 3 - Oxygen Flashcards
Reaction centres in photosynthesis
Both type 1 and type 2 were present in the ancestor bacteria.
Evolution occured and the types split up.
Type 1 centres
Present in heliobacteria and green sulfur bacteria.
Contain iron-sulfur (Fe-S) proteins at the bottom.
AKA photosystem 1 (??)
Type 2 centres
Present in purple bacteria and green non-sulfur bacteria.
Contain cytochromes made from iron on top of them.
AKA photosynthesis 2 (??)
Type 1 and type 2 reaction centres rejoining
At some point as evolution ocurred, type 1 and type 2 reaction centres joined up again and worked together to do photosynthesis
Stromatolites
Stromatolites are made from cyanobacteria and are the oldest known macrofossils, dating back over 3 billion years.
They Dominate the fossil record for 80% of Earth history and they are an important source of information on the early development of life on Earth and possibly other planets.
Iron oxides and oxygen production
As oxygen was produced, it reacted with iron to form iron oxides.
By separating the trapped from the iron, we can see what the oxygen was like billions of years ago.
Negatives of oxygen (chemical)
When oxygen oxidises iron (Fe²⁺ to Fe³⁺), it generates superoxides (oxygen free radicles)
Superoxides react with hydrogen to form hydrogen peroxide (bleach)
When hydrogen peroxides oxidises Fe²⁺, it forms a hydroxyl radical which is very reactive.
Negatives of oxygen (world)
Thought to have caused a mass extinction event.
Positives of oxygen (chemical)
Allows for aerobic respiration to occur, which produces around 16x more ATP in profit than anaerobic respiration.
Positives of oxygen (worldwide)
Formed the ozone layer
As oxygen reacted with UV light in the atmosphere, it created radicles that would react with more oxygen and form ozone. This new ozone layer would act as a barrier from the most harmful UV rays and allow life to exist out of water.
