1. The largest amino acid is Trp.
   
2. Asp is the most acidic. Glu is rather acidic too, but Asp beats it by 0.1 pKa unit. (In chemistry pKa is a measure for acidity. The lower the pKa, the more acidic.)
   
3. Gly is the smallest.
   
4. Gly is also the one without a chiral center. A carbon is chiral if it has 4 different groups bound to it. All α-carbons are chiral, and so are the Cβs of Ile and Thr. Gly has two protons on its Cα and is thus not chiral.
   
5. In proline we find an unusual bond between the backbone N and the side chain Cδ.
   
6. Histidine has two Nitrogens in its side chain that can donate or accept protons (depending on the pH). And that makes it a very good buffer.
   
7. Ile, Thr, and Val are β-branched. Alifatic means "contains only non-aromatic carbons". So it is Ile.
   
8. Even though Pro has a ring, it is not aromatic.
   
9. Cys can form Cys-Cys bridges.
   
10. A sequence begins with the N-terminal residue and ends with the C-terminal one. So it is Asp.
11. Gly doesn't have a real side chain. So its Φ and Ψ rotations are unrestricted. That makes it very flexible.
    
12. Proline cannot rotate around its Φ angle because of the extra, ring-forming bond of the backbone N with the side chain Cδ. That makes it very restricted in its conformations.
    
13. Cysteine can form bridges, can bind metals, can be oxidized. So it is very reactive.
    
14. The last to questions get each time another molecule in the window, so I cannot give the answers here.
    

The last question in the quiz gives every day another picture so I cannot type the answer...