Viruses are particles of dna surrounded by a protein coat in which way do viruses depend on living cells

Viruses need to infect living cells of other organisms in order to replicate their genetic material. When not in an infected living cell, they are considered independent particles, in the form of DNA surrounded by a protein coat. Only when a virus enters and infects a living cell, it can then start its reproductive cycle. It uses the host's (infected cell) replication system, to replicate its own DNA or RNA and create the necessary viral proteins to create more viruses. The newly created viruses are then able to infect other living cells. 

If it doesn't have a nucleus its a prokaryote

This type of galaxy is an approximately ellipsoidal shape and a smooth, nearly featureless image. they are the largest single star systems, in the universe and are built by the collisions of many smaller galaxies.