<Tr> <Td> Fe </Td> <Td> ~ 10 (Fe (II)) </Td> <Td> ~ 10 (Fe (III)) </Td> </Tr> <Tr> <Td> Co </Td> <Td> ~ 10 </Td> <Td> ~ 10 </Td> </Tr> <Tr> <Td> Ni </Td> <Td> <10 </Td> <Td> <10 </Td> </Tr> <Tr> <Td> Cu </Td> <Td> <10 (very low) (Cu (I)) </Td> <Td> <10 (Cu (II)) </Td> </Tr>

3 molecules used in biology that have metal ions in their structure