What do these words "ah", "eh", and "oh" do in a Tagalog sentence?

They would go like this:

Case 1: "Nandun lang 'yon eh!" or "Sarado na eh!"

Case 2: "Nandun lang 'yon ah!" or "Sarado na ah!"

Case 3: "Nandun lang 'yon oh!" or "Sarado na oh!"

I rarely spot them in an ordinary discourse. Here are my questions:

• For what instances they should be used?

• And what do they actually mean?

• Can the sentences stand without them? And still mean the same?

• Should the words always have to be uttered with a high tone (like singing)?

Sorry for a lot of questions. Just a curious dayuhan.