Meisenberg: Principles of Medical Biochemistry, 3Rd Edition

Meisenberg: Principles of Medical Biochemistry, 3rd Edition

Chapter 1: Introduction to Biomolecules

Test Bank

MULTIPLE CHOICE

1. β Linkages are important in structural polysaccharides because:

a. / They are easily hydrolyzed by glycosidase enzymes.
b. / They allow the chains to form compact coils.
c. / They cause the chains to exist in an extended form, thus allowing them to form fibers.
d. / They cause the chains to absorb more water.
e. / They can be formed by any hydroxy group in the monomer, whereas a linkages can be formed only by C-1.

ANS: C

Cellulose, chitin, and peptidoglycan are examples of fibrous polysaccharides that are formed from β-linked units.

2. What is the difference between α-D-glucose and α-D-galactose?

a. / They are mirror images of each other.
b. / They differ in the configuration of substituents at C-4.
c. / One is an aldose and the other is a ketose.
d. / They are anomers.
e. / One forms only O-glycosidic bonds, and the other forms only N-glycosidic bonds.

ANS: B

Galactose is a C-4 epimer of glucose (and vice versa). Epimers are not mirror images of one another because other asymmetrical carbons are also present in the molecule.

3. What is the major difference between glycogen and amylose?

a. / Glycogen contains only glucose, and amylose contains some fructose in addition to glucose.
b. / Glycogen is a storage polysaccharide, and amylose is a structural polysaccharide of the extracellular matrix.
c. / Glycogen is branched, and amylose is not.
d. / Glycogen contains some β linkages, but amylose contains only α linkages.
e. / Glycogen is stored in the liver, and amylose is stored in skeletal muscle.

ANS: C

Glycogen is a branched polysaccharide similar to amylopectin, a form of starch that is found together with unbranched amylose in the starch granules of plants.

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Test Bank

4. Unlike covalent bonds, all noncovalent interactions are:

a. / Formed in irreversible reactions.
b. / Constantly forming and breaking on the molecular time scale.
c. / Susceptible to cleavage by strong acids and bases.
d. / Classified as energy-rich, because they are cleaved easily.
e. / Independent of the solvent that surrounds the bond-forming groups.

ANS: B

Because noncovalent bonds form and break constantly, all noncovalent interactions are reversible.