Water, pH, and Biological Molecules

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Questions and Answers

Why are nonpolar biomolecules poorly soluble in water?

They form stronger water-water interactions, excluding the nonpolar molecules.
They readily replace water-water interactions, leading to their aggregation.
They interfere with water-water interactions but cannot form energetically favorable water-solute interactions. (correct)
They increase the dielectric constant of water, reducing its ability to dissolve solutes.

How does the geometry of a water molecule contribute to its unique properties?

Its tetrahedral arrangement of electron orbitals results in a polar molecule with strong cohesive properties. (correct)
Its spherical symmetry minimizes intermolecular interactions, leading to a high vapor pressure.
Its linear shape allows for maximum hydrogen bonding capacity.
Its trigonal planar structure allows it to effectively dissolve nonpolar substances.

What is the significance of van der Waals interactions in biological molecules?

They enable the formation of strong covalent bonds between lipids and carbohydrates.
They contribute to the specific, three-dimensional structures of proteins, nucleic acids, polysaccharides and membrane lipids. (correct)
They facilitate the solubility of nonpolar molecules in aqueous environments.
They provide the primary force for protein folding and stabilization of nucleic acid structures.

Why is it important to consider equilibrium constants for ionization reactions in biological systems?

To predict the state of ionization of solutes in water, which affects their behavior and interactions. (C) Signup and view all the answers

How does the autoionization of water influence pH calculations?

It establishes a fixed relationship between [H+] and [OH-], allowing pH calculation if either concentration is known. (C) Signup and view all the answers

What is the chemical characteristic of a buffer system and explain how this relates to the system's function?

A mixture of a weak acid and its conjugate base, resisting changes in pH by neutralizing added acid or base. (C) Signup and view all the answers

How does the Henderson-Hasselbalch equation relate the pH of a solution to the pKa of a weak acid within that solution?

It mathematically relates pH to the pKa and the ratio of the concentrations of the acid and its conjugate base. (D) Signup and view all the answers

Considering the role of water in biological systems, what implications arise from its high heat of vaporization?

Organisms can efficiently dissipate excess heat through evaporation, maintaining stable internal temperatures. (B) Signup and view all the answers

How do the unique solvent properties of water influence the structure and function of proteins?

Water's polarity facilitates the formation of hydrogen bonds, stabilizing protein structure and enabling enzyme-substrate interactions. (B) Signup and view all the answers

In multicellular organisms, pH regulation within the extracellular fluids is tightly controlled. What is primarily responsible for achieving this constant pH?

The presence of biological buffers, which are mixtures of weak acids and their conjugate bases. (C) Signup and view all the answers

Flashcards

Importance of Water Properties

The physical and chemical characteristics of water influence cellular structure and function.

Role of weak interactions

Weak individually, but collectively strong influencers of biomolecule structure.

Water's Internal Cohesion

Attractions between adjacent water molecules that give liquid water great internal cohesion.

van der Waals Interactions

Weak interatomic interactions when uncharged atoms are very close; electron clouds influence each other, creating transient dipoles.