Read the following statements and choose the correct answer.
A. Cellulose is a branched structural polysaccharide.
B. GLUT-4 is a heteropolymer.
C. Zinc ions are required for catalytic activity of salivary amylase.
Solution:
Let's analyze each statement:
A. Cellulose is a branched structural polysaccharide. This statement is incorrect. Cellulose is an unbranched homopolymer of glucose units linked by β-1,4 glycosidic bonds. Starch (amylopectin) and glycogen are examples of branched polysaccharides.
B. GLUT-4 is a heteropolymer. This statement is correct. GLUT-4 (Glucose Transporter Type 4) is a protein. Proteins are polymers made up of different types of amino acids (typically 20 different types), hence they are considered heteropolymers.
C. Zinc ions are required for catalytic activity of salivary amylase. This statement is incorrect. Salivary amylase (ptyalin) requires chloride ions (Cl-) for its optimal catalytic activity, not zinc ions. Zinc ions act as cofactors for many other enzymes, such as carbonic anhydrase and alcohol dehydrogenase.
Based on the analysis, only statement B is correct.