Properties of water in biochemistry: Which listed statement does NOT correctly describe liquid water?
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AThe water molecule is asymmetric (bent geometry).
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BWater readily forms hydrophobic interactions.
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CThe O–H covalent bonds in water are highly polarized.
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DAll three atoms in H2O can participate in hydrogen bonding.
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EWater has a significant dipole moment.
Answer
Correct Answer: Water readily forms hydrophobic interactions.
Explanation
Introduction / Context:Water’s unique properties drive protein folding, membrane assembly, and acid–base chemistry in life. Distinguishing hydrophilic from hydrophobic effects is essential for understanding biomolecular structure.
Given Data / Assumptions:
- Liquid water near room temperature.
- Hydrogen bonding network among molecules.
- Hydrophobic interactions occur among nonpolar solutes in water.
Concept / Approach:Water is polar and forms extensive hydrogen bonds. Hydrophobic interactions are not bonds formed by water; rather, they are entropy-driven associations of nonpolar molecules that minimize disruption of water’s hydrogen-bonded network. Thus, saying “water readily forms hydrophobic interactions” is incorrect; water drives hydrophobes together but does not “form” those interactions itself.
Step-by-Step Solution:Recall geometry: bent, asymmetric; strong dipole.Recognize hydrogen-bond donors/acceptors: H (donor) and O lone pairs (acceptor).Identify the false statement: water forming hydrophobic interactions.
Verification / Alternative check:Consider oil droplets coalescing in water; the driving force is water’s preference to hydrogen bond with itself, excluding nonpolar surfaces.
Why Other Options Are Wrong:
- Asymmetry/polar bonds/dipole: All true.
- Hydrogen-bonding by all atoms: Oxygen accepts; hydrogens donate; net effect involves all three atoms.
Common Pitfalls:Equating “hydrophobic interaction” with a physical bond type; it is an emergent thermodynamic phenomenon.
Final Answer:Water readily forms hydrophobic interactions.