lesson 3

• What is the most important and abundant inorganic compound in the biosphere?


  Water
• In how many states is water present?


  Three states
• What percentage of water is liquid in the biosphere?

  97%
• How does the water content of the human body change with age?


  It decreases with age
• Why is maintaining the correct balance of fluid in the body crucial to health?


  It is essential for proper physiological functions
• What is dehydration defined as?


  A 1% or greater loss of body mass due to fluid loss
• What is the angle of the water molecule?


  104.5º
• What type of structure does the water molecule form?

  Almost a perfect tetrahedron
• What is the electronegativity difference in the water molecule?


  Oxygen is more electronegative than hydrogen
• What type of interactions are responsible for the strength and specificity of biomolecule recognition?

  Non-covalent interactions influenced by water's solvent properties
• How do hydrogen bonds affect the properties of water?


  They are responsible for water being liquid at room temperature
• How many hydrogen bonds can each water molecule form?


  Four hydrogen bonds
• What is the lifetime of each hydrogen bond in water?


  10^-12 seconds
• What is the equilibrium constant of water (Keq)?


  1. 8 x 10^-16 M
• What happens to water molecules in the ionization process?


  They separate into hydronium (H3O+) and hydroxyl ions (OH-)
• What is the ion product of water (Kw) at 25ºC?


  1 x 10^-14 M
• What is the pH of pure water?


  7
• What does a decrease in pH indicate?


  Increased acidity
• What is the relationship between pH and [H+] concentration?


  As [H+] increases, pH decreases
• What does the pH scale measure?


  The concentration of hydrogen ions (H+) in a fluid
• What is the physiological pH range for human blood?


  1. 35 to 7.45
• What is acidosis in terms of blood pH?


  A blood pH of 7.35 or lower
• What is alkalosis in terms of blood pH?


  A blood pH above 7.45
• What is the significance of the pH optimum for enzymes?


  It is the pH at which enzymes have maximal activity
• What defines a weak acid according to the Arrhenius definition?


  A substance that dissociates in protons (H+) in water
• What defines a weak base according to the Arrhenius definition?


  A substance that dissociates in hydroxide ions (OH-) in water
• What is an amphoteric compound?


  A substance that can act as both an acid and a base
• How do amino acids behave in neutral aqueous solutions?


  They exist in zwitterionic form
• What happens to the pH when an acid is added to an aqueous solution?


  The pH decreases
• What happens to the pH when a base is added to an aqueous solution?


  The pH increases
• What is the relationship between strong acids and their conjugate bases?


  The stronger the acid, the weaker its conjugate base
• What is the significance of the acid dissociation constant (Ka)?


  It measures the strength of a weak acid
• How does the pKa relate to the strength of an acid?


  Lower pKa values indicate stronger acids
• What is the relationship between Ka and pKa?


  pKa = -log(Ka)
• What are the key properties of water that influence biological systems?

  • High solvent capability
  • Cohesion and adhesion
  • High surface tension
  • Ability to form hydrogen bonds
• What are the definitions of acids and bases according to the Arrhenius and Bronsted-Lowry theories?


  • Acid (Arrhenius): Dissociates in water to produce H+
  • Acid (Bronsted-Lowry): Proton donor
  • Base (Arrhenius): Dissociates in water to produce OH-
  • Base (Bronsted-Lowry): Proton acceptor
• What are the characteristics of weak acids and bases?

  • Weak acids: Partially ionized in solution, characterized by Ka
  • Weak bases: Partially ionized in solution, characterized by Kb
• What is the significance of the dissociation constant (Ka) and its relationship to pKa?


  • Ka measures the strength of a weak acid
  • Lower pKa values indicate stronger acids
• How do weak acids and bases behave in solution?


  • Weak acids: Partially dissociate, establishing equilibrium
  • Weak bases: Partially dissociate, establishing equilibrium
• What is the role of buffers in biological systems?


  • Maintain stable pH levels
  • Resist changes in pH upon addition of acids or bases