Irreversible precipitation of proteins is called

At the isoelectric point:

The compound with the formula $NH_2CH_2COOH$ acts as:

Which of the following contains the highest percentage of protein?

$A$ codon has a sequence of $\underline{A}$,and specifies a particular $\underline{B}$ that is to be incorporated into a $\underline{C}$. What are $\underline{A}, \underline{B}, \underline{C}$?
$\underline{A} \quad \underline{B} \quad \underline{C}$

What are the common types of secondary structure of proteins?