Structural changes in globular proteins due to extreme $pH$ or temperature are known as:

Which bond connects two amino acids?

Which of the following statements correctly describe the functions of proteins?
$(I)$ As an enzyme
$(II)$ As a hormone
$(III)$ Fight against infectious organisms
$(IV)$ Formation of genetic material

How many polypeptide chains are present in the structure of hemoglobin?

Match the following Column-$I$ with Column-$II$ and select the correct option.

Column-$I$ (Type of Amino Acid)	Column-$II$ (Example)
$(A)$ Polar and uncharged $R$ group	$(i)$ Methionine
$(B)$ Non-polar $R$ group	$(ii)$ Glutamic acid
$(C)$ Polar and negatively charged $R$ group	$(iii)$ Lysine
$(D)$ Polar and positively charged $R$ group	$(iv)$ Cysteine

Casein present in milk is a/an .......