http://en.wikipedia.org/wiki/Cyanobacteria
Scroll to photosynthesis and read. Then think about how most plants and algae use chloroplasts to photosynthesise.
Cellular examination of a cyanobacterium and a diatom reveals that the diatom has (which structure?) that is absent in the cyanobacterium?
a. DNA
b. chloroplasts
c. plasma membrane
d. a cell wall with peptidoglycan
e. all of the above