Biochemistry Multiple Choice Questions - Weak interactions in Aqueous Systems

11. Which of these statements about hydrogen bonds is not true?
a) Hydrogen bonds account for the anomalously high boiling point of water.
b) In liquid water, the average water molecule forms hydrogen bonds with three to four other water molecules.
c) Individual hydrogen bonds are much weaker than covalent bonds.
d) Individual hydrogen bonds in liquid water exist for many seconds and sometimes for minutes.
e) The strength of a hydrogen bond depends on the linearity of the three atoms involved in the bond.
Ans: d

12. A true statement about hydrophobic interactions is that they:
Hydrophobic interactions
a) are the driving force in the formation of micelles of amphipathic compounds in water.
b) do not contribute to the structure of water-soluble proteins.
c) have bonding energies of approximately 20–40 Kjoule per mole.
d) involve the ability of water to denature proteins.
e) primarily involve the effect of polar solutes on the entropy of aqueous systems.
Ans: a

13. Hydrophobic interactions make important energetic contributions to:
a) binding of a hormone to its receptor protein.
b) enzyme-substrate interactions.
c) membrane structure.
d) three-dimensional folding of a polypeptide chain.
e) all of the above are true.
Ans: e

14. Dissolved solutes alter some physical (colligative) properties of the solvent water because they change the:
a) concentration of the water.
b) hydrogen bonding of the water.
c) ionic bonding of the water.
d) pH of the water.
e) temperature of the water.
Ans: a

15. Osmosis is movement of a:
a) charged solute molecule (ion) across a membrane.
b) gas molecule across a membrane.
c) nonpolar solute molecule across a membrane.
d) polar solute molecule across a membrane.
e) water molecule across a membrane.
Ans: e

Reference: Lehninger Principles of Biochemistry Fourth Edition (Nelson and Cox)

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