Primitive earth reactions

Question 1

In what forms was iron present in primitive earth

Answer 1

• Fe2+ incorporated into many enzymes

* Fe III/FeII couple used to catalyse one-electron redox reactions

Question 2

Avaiability of Zn in primitive earth

Answer 2

• Zn available as Zn2+ and used in enzymes to catalyse acid base reactions

Question 3

Availability of Cu in primitve earth

Answer 3

• Cu was unavailables
• present as the native metal Cu(s)
• Cu+ and Cu2+ were very toxic
- toxic when they were free and not bound to anything like proteins because they can reduce oxygen to radicals

Question 4

Availability of copper in evolved earth

Answer 4

• Cu(s) wsa oxidised to Cu+ and Cu2+ and became available to biology
• CuII/CuI couple used to catalyse one electron redox reactions in enzymes

Question 5

Why are free copper ions toxic?

Answer 5

• Cu+ reduce O2 catalytically by 1e into superoxide ions

* reuduces H2O2 catalytically by 1e into hydroxyl radicals

Question 6

Main differences between primitive earth and evolved earth?

Answer 6

Primitive
• no O2
• Fe used to catalyse one electron redox reactions
• Cu unavailable

Evolved
• O2 available
• CuII/CuI used to catalyse one electron redox reactions
• Cu2+ and Cu+ became available to biology