I need help on some simple chemistry questions

I'm taking AP Biology as a sophomore and it requires some knowledge over Chem. I am CLUELESS and I have a few q's. please help, thanks ! :))

1.A(n)_________ is a special chemical that has the ability to regulate a solution's pH. If a solution is too acidic is will ________ H+.

2. All solutions contains the ________ and the _________.

3. There are 20 different amino acids, all with the same basic structure. What is responsible for the different chemical properties of these different amino acids?

4. What is the double bonded oxygen [COO-] called?

1. buffer ... reduce
2. solute and solvent
3. the different side chains
4. C=O is the carbonyl. The carbonyl together with a hydroxyl makes the carboxyl group

1.) buffer, lose
2.) solvent, solute
3.) functional group
4.) carboxyl group:
..O
..||....._
-C-O (the dots are used for spacing - this space doesn't allow for spacing over)
(the O has a negative 1 charge)
(the C is double bonded to an O and singly bonded to the other O with the negative 1 charge)

I was assuming you meant the entire [COO-] not just the C=O

1 Buffer and reduce
2 solvent and solute
3 side chain
4 carboxyl