Which element is common in both hemoglobin and myoglobin?

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

Which of the following amino acids contains a polar and positively charged '$R$' group?

Non-essential amino acids are:

The spiral configuration of $\alpha$-helix and $\beta$-pleated sheet of polypeptide chains are held together by . . . . . . bonds to form the secondary structure of protein.

Match the following.

Column-$I$	Column-$II$
$A$. Trypsin	$1$. Intercellular ground substance
$B$. $GLUT-4$	$2$. Hormone
$C$. Insulin	$3$. Enzyme
$D$. Collagen	$4$. Enables glucose transport into cells