Structure of Water and Hydrogen Bonding：練習題

A polypeptide is synthesized through a series of dehydration reactions. If a protein consists of 120 amino acids arranged in a single linear chain, what is the total number of water molecules released during its formation, and what is the resulting number of peptide bonds formed?

In an investigation of the properties of water, a student observes that a water strider can walk on the surface of a pond without sinking. At a molecular level, this phenomenon is best explained by the fact that at the air-water interface, water molecules are:

A researcher analyzes a macromolecule isolated from a bacterial cell wall. The analysis reveals the presence of nitrogenous components and various six-carbon sugars linked by peptide bonds. Further investigation shows that this molecule provides structural support against osmotic pressure. Which of the following best describes the chemical bonds primarily responsible for the strength of this macromolecule?

Which of the following best explains why water has a high specific heat and how this property contributes to biological homeostasis?

Analyze the following data regarding the elemental composition of four unknown biological samples. Sample A contains 1:2:1 ratio of C:H:O. Sample B contains C, H, O, N, and P. Sample C contains C, H, O, and N. Sample D contains C, H, and very little O. Which sample is most likely a nucleotide-based signaling molecule like cAMP?

Explain how the unique properties of hydrogen bonding between water molecules contribute to the process of transpirational pull in the xylem of vascular plants.

In a hypothetical population of beetles, a mutation leads to a change in the primary structure of a chitin-binding protein where glutamic acid (polar, acidic) is replaced by valine (non-polar). Predict how this substitution affects the tertiary structure of the protein and the resulting fitness of the individual in an environment with high fungal pathogen exposure.

Water is essential for life due to its unique chemical properties, which stem from its polar covalent bonds and the resulting hydrogen bonding between molecules.

(a) Describe the property of adhesion and explain how it differs from cohesion in the context of water movement in plants.
(b) Explain why water has a high specific heat capacity and discuss why this property is biologically important for aquatic organisms.