Why are phytoplankton essential to aquatic life zones?
select one:
a. filter pollution from water
b. provide basis of food chains
c. moderate water temperature
d. produce chemicals that can be used against predators

Protein and polypeptide sequences can be determined by first partially hydrolyzing the protein or polypeptide followed by amino acid sequencing of the fragment pieces using the chemical degradation process known as edman degradation. determine the sequence of the initial (18-amino acid) polypeptide that produces the following five partial sequences after hydrolysis and edman degradation.