Biological Molecules

• How do hydrogen bonds form between water molecules?

  Hydrogen bonds form due to the polar nature of water, where oxygen is more electronegative than hydrogen.

  
• What is the significance of the partial charges in water molecules?

  The partial negative charge on oxygen and partial positive charge on hydrogen allow for intermolecular attractions.
• What are the 7 biologically important properties of water?

  • Reaches maximum density at 4℃
  • High surface tension
  • Incompressible
  • Metabolite/solvent for chemical reactions
  • High specific heat capacity
  • High latent heat of vaporization
  • Cohesion between molecules
• Why is the incompressible nature of water important for organisms?

  It provides turgidity to plant cells and a hydrostatic skeleton for some small animals.
• Why does ice float on water, and why is this important for organisms?

  Ice is less dense than water due to hydrogen bonds holding molecules in fixed positions, insulating aquatic life.
• How does the high surface tension of water benefit organisms?

  It slows water loss in plants and allows some insects to skim across the surface.
• Why is water considered an important solvent for organisms?

  Water is a polar universal solvent that dissolves and transports charged particles for biochemical reactions.
• What is the significance of water's high specific heat capacity and latent heat of vaporization for organisms?

  These properties help maintain stable temperatures and provide cooling effects through evaporation.
• How do hydrogen bonds form between water molecules?

  Water is polar: O is more electronegative than H, so it attracts electron density in the covalent bond more strongly. This forms O 𝛿- (slightly negative) and H 𝛿+ (slightly positive). There are intermolecular forces of attraction between a lone pair on O 𝛿- of one molecule and H 𝛿+ on an adjacent molecule.

  
• State 7 biologically important properties of water.

  The 7 biologically important properties of water are:

  1. Reaches maximum density at 4°C
  2. High surface tension
  3. Incompressible
  4. Acts as a metabolite and solvent for chemical reactions in the body
  5. High specific heat capacity
  6. High latent heat of vaporization
  7. Cohesion between molecules
• Why is the incompressible nature of water important for organisms?

  The incompressible nature of water provides turgidity to plant cells and a hydrostatic skeleton for some small animals like earthworms.
• Explain why ice floats on water. Why is this important for organisms?

  Ice is less dense than water because the hydrogen bonds hold the water molecules in fixed positions further apart from each other. This insulates the water in arctic climates so aquatic organisms can survive, as the water acts as a habitat.
• Why is the high surface tension of water important for organisms?

  The high surface tension of water slows water loss due to transpiration in plants, allows water to rise unusually high in narrow tubes (reducing demand on root pressure), and enables some insects to skim across the surface of water.
• Why is water an important solvent for organisms?

  Water is a polar universal solvent that can dissolve and transport charged particles involved in intra- and extracellular reactions, such as phosphate ions (PO4^3-) for DNA synthesis.
• Why are the high specific heat capacity and latent heat of vaporization of water important for organisms?

  The high specific heat capacity and latent heat of vaporization of water act as a temperature buffer, enabling endotherms to resist fluctuations in core temperature to maintain optimum enzyme activity. The cooling effect when water evaporates from the skin surface as sweat or from the mouth when panting is also important.
• Define monomer and polymer. Give some examples.

  A monomer is a smaller unit that joins together to form a larger molecule, while a polymer is a molecule formed when many monomers join together. Examples of monomers include monosaccharides (glucose, fructose, galactose, ribose), amino acids, and nucleotides. Examples of polymers include polysaccharides, proteins, and DNA/RNA.
• What happens in condensation and hydrolysis reactions?

  In a condensation reaction, a chemical bond forms between two molecules and a molecule of water is produced. In a hydrolysis reaction, a water molecule is used to break a chemical bond between two molecules, such as the peptide bonds in proteins or the ester bonds between fatty acids and glycerol in lipids.

  
• Name the elements found in carbohydrates, lipids, proteins and nucleic acids.

  Carbohydrates and lipids contain the elements carbon (C), hydrogen (H), and oxygen (O). Proteins contain the elements carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S). Nucleic acids contain the elements carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P).

  
• Draw the structure of α-glucose and β-glucose.

  Both α-glucose and β-glucose are hexose monosaccharides (6 carbon atoms) with a ring structure. α-glucose has a cis isomer configuration, while β-glucose has a trans isomer configuration.

  
• Describe the properties of α-glucose.

  α-glucose is a small, water-soluble molecule that is easily transported in the bloodstream. Its complementary shape allows it to bind to transport proteins for absorption in the gut, and its complementary shape to enzymes makes it a respiratory substrate for glycolysis.

  
• Draw the structure of ribose.

  Ribose is a pentose monosaccharide (5 carbon atoms) with a ring structure.