Proteins perform a diverse of functions and the function of a protein is determined by its tertiary structure. The enzymes are proteins that mediate catalysis of protein molecule sin the process of digestion.
Proteins are the main structural components of muscles. They also serve as significant contributions to energy resource, protein catabolism mainly occurs during fasting or excessive muscular activity.
Other functions of proteins include, they work as enzymes (Eg: pepsin), hormones (Eg: insulin) and receptors (Eg: membrane receptors.). The hormones are not only proteins but some of them are steroidal type. Keratin is protein but do not mediate any emzymatic catalysis.
Thus, the options (a), (b) and (d) are incorrect.
Proteins perform a diverse of functions and the function of a protein is determined by its tertiary structure. The enzymes are proteins that mediate catalysis of protein molecule sin the process of digestion.
Therefore, the correct option is – c. enzymes.