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Which property of proteins enables them to act as pH buffers?

Correct answer: B. They contain carboxyl and amino groups

  • A. They are insoluble
  • B. They contain carboxyl and amino groups
  • C. They have a low molecular mass
  • D. They possess only secondary structure

Explanation

Option B is correct. Proteins act as pH buffers due to their amphoteric nature, meaning they can function as both acids and bases. This is because the amino acids that compose proteins have both carboxyl groups (-COOH), which can donate hydrogen ions, and amino groups (-NH2), which can accept hydrogen ions. This dual capability allows proteins to stabilize pH changes in biological systems.Option A is incorrect because solubility is not the property that enables buffering. Option C is incorrect as molecular mass is not related to buffering capacity. Option D is incorrect because the buffering ability is not tied to a single structural level of proteins but to the presence of specific functional groups.

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The chapter covers water's polarity and biological roles, carbohydrates, lipids, proteins and nucleic acids, including their monomers, bonds, structures and functions. It also distinguishes RNA from DNA and explains conjugated molecules such as glycoproteins, glycolipids and nucleoproteins, which combine organic molecules with a non-protein component.

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