As for your second question, read
this. The first 3 posts on that page relate to your question; I asked that exact same question a while ago! chrisjb helped me out there. It's not a complete answer, just a way of tackling the question.
Help pleaseee
"Explain how the role and structure of the Senate provides for responsible Government" [4 marks]
I would say something along the lines of; the Senate provides for a Responsible government, as its' main role is to review legislation to improve Bills with amendments or to defeat unwise legislation. In this way, it ensures that any bill passed by the government (Government bill)/House of Representatives is appropriate/responsible. The structure of the Senate also provides for a Responsible government as it represents the interest of the states - equal representation; 12 from each state, and 2 from each territory. If citizens are not satisfied with the role of some senators, they won't be re-elected.
It's by no means the greatest answer, just my shot at answering the question. It's a different question. I'm not really sure how to relate the structure of the Senate to Responsible government though. =[ Someone else can probably give a better answer than me.