No cell could live without

What type of amino acids are phenylalanine and tyrosine,respectively?

Simple proteins bonded with a non-proteinic prosthetic group (acting as cofactor) are called:

Which structure of a protein represents its three-dimensional form?

Find the correct option for the sequence given below:
$(1)$ Alanine $\rightarrow$ Valine
$(2)$ Asparagine $\rightarrow$ . . . . . .
$(3)$ Aspartic acid $\rightarrow$ Glutamic acid
$(4)$ Arginine $\rightarrow$ Histidine

Attempt titrating an amino acid against a weak base and discover the number of dissociating (ionizable) functional groups in the amino acid.