Which among the following is a basic amino acid?

Which of the following are protein fibers?

Proteins are $.......$.

Protein found in a biological system with a unique three-dimensional structure and biological activity is called a native protein. When a protein in its native form is subjected to a physical change like a change in temperature or a chemical change like a change in $pH$,denaturation of proteins takes place. Explain the cause.

Structures of alanine at $pH = 2$ and $pH = 10$ are respectively

Which of the following proteins destroys the antigen when it enters a body cell?