Biochem:water/carbohydrates

• Water is known as the "universal solvent" and is colorless, tasteless, and the most abundant surface on Earth
• Water is the only common substance that exists naturally as a solid, liquid, and gas
• Water molecules are extremely polar and form hydrogen bonds
• A hydrogen bond is a relatively strong and attractive interaction that occurs between a hydrogen atom bonded to a highly electronegative atom and another electronegative atom in a different molecule or within the same molecule
• Main Properties Of Water:

  • Water has high polarity, which is the distribution of electrical charge among atoms connected by a chemical bond
  • Water has high specific heat, which is the amount of heat energy required to raise the temperature of a substance by a certain amount
  • Water has a high heat of vaporization, which is the amount of energy required to transform a quantity of a liquid into a gas
  • Water has low density as a solid, resulting in its unique hydrogen bonding arrangement that creates a hexagonal lattice structure with large gaps between water molecules
• • Water is attracted to other polar molecules due to its polarity and hydrogen bonding
  • Water exhibits cohesion and surface tension due to hydrogen bonding between water molecules, allowing water to "stick" to itself and resist external forces
  • Water has solvent properties due to its polarity, enabling it to dissolve a wide range of substances
  • Water has a high melting point of 0 degrees Celsius at standard atmospheric pressure
• Hydrogen bonds are relatively strong intermolecular forces that require a significant amount of energy to break
• The high heat capacity of hydrogen bonds allows water to absorb and store a lot of heat energy without causing a significant increase in temperature
• The high heat of vaporization of water allows it to absorb heat from its surroundings when it evaporates, contributing to cooling effects and moderating temperature changes
• The low density of water as a solid has a profound impact on aquatic ecosystems, insulating bodies of water and preventing them from freezing completely in cold temperatures
• Water's attraction to other polar molecules is due to its polarity and hydrogen bonding
• Cohesion and surface tension in water are a result of hydrogen bonding between water molecules, allowing water to resist external forces and exhibit surface tension
• Water's solvent properties are due to its polarity, enabling it to dissolve a wide range of substances
• Water has a high melting point of 0 degrees Celsius at standard atmospheric pressure, requiring the disruption of hydrogen bonds for the solid ice to transition into the liquid state
• Water is amphoteric, meaning it can act as an acid or base, and its pH can be affected by dissolved carbon dioxide gas or minerals like calcium carbonate
• Self-ionization of water refers to the process where water molecules react with each other to form hydronium ions and hydroxide ions, with an equilibrium constant known as the ionization constant or Kw
• The ionization constant of water (Kw) is a measure of the extent of self-ionization and is equal to the product of the concentrations of hydronium and hydroxide ions in a solution at a given temperature
• At 25°C, the Kw of water is approximately 1.0 x 10^-14 M, indicating the product of hydronium and hydroxide ions in any aqueous solution at this temperature will always be constant
• At 25°C (298 K), the Kw of water is approximately 1.0 x 10⁻¹⁴ M
• The product of the concentrations of hydronium and hydroxide ions in any aqueous solution at this temperature will always equal to 1.0 x 10⁻¹⁴ M
• Water is identified as a Brønsted-Lowry acid or a Brønsted-Lowry base based on its reactions with other substances
• Examples of reactions involving water:

  • H₂O(ℓ) + NO₂⁻(aq) → HNO₂(аq) + OH⁻(aq)
  • HC₂H₃O₂(aq) + H₂O(ℓ) → H₃O⁺(aq) + C₂H₃O₂⁻(aq)
  • HCOOH(aq) + H₂O(ℓ) → H₃O⁺(aq) + HCOO⁻(aq)
  • H₂O(ℓ) + PO₄³⁻(aq) → OH⁻(aq) + HPO₄²⁻(aq)
• The relationship among pH, pOH, and pKw:

  • pH = 14 - pOH
  • pOH = 14 - pH
  • Kw = [H₃O⁺] [OH⁻]
  • To calculate: Press Shift log -pH
• Given [H₃O⁺] concentration of 2x10^-6 M at 25°C, calculate the [OH⁻] concentration
• Given [H₃O⁺] concentration of 3x10^-5 M, determine if the solution is acidic, basic, or neutral
• Examples of problem-solving:

  1. Calculate the pH of a solution with [H⁺] concentration of 1.35 x 10^-2 M

  2. Find the H⁺ concentration of an acid with a pH of 3.4

  3. Determine:

  a. H₃O⁺ in rainwater with a pH of 4.35

  b. OH⁻ concentration in ammonia with a pH of 11.28

  4. Calculate the pH value of a 0.0045 M HCl solution
• Try these calculations:

  1. Find the H⁺ concentration of a substance with an OH⁻ concentration of 5.62 x 10^-4 M

  2. Determine:

  a. H⁺ concentration of yogurt with a pH value of 2.85

  b. OH⁻ concentration of yogurt

  3. Calculate the OH⁻ and H⁺ of each solution:

  a. 0.00165 M HNO₃ (find [OH⁻])

  b. 0.0087 KOH (find [H₃O⁺])

  4. Calculate the pH value of a 6.14 x 10^-4 M HNO₃ solution
• Additional calculations:

  1. Calculate the OH⁻ and H⁺ of each solution:

  a. 0.000213 M Sr(OH)₂ (find [H⁺])

  b. 5.8 x 10^-4 M HI (find [OH⁻])

  2. Calculate the pH value of each solution:

  a. 0.0083 M NaOH

  b. 4.8 x 10^-3 M Ba(OH)₂
• Buffer solutions:

  • A buffer can resist pH changes upon the addition of acidic or basic components
  • It neutralizes small amounts of added acid or base, maintaining the solution's pH relatively stable
  • Acts as an acid or base shock absorber
• Examples of buffer systems:

  1. Calculate the pH of a buffer system with 0.15 M NH₃ and 0.35 M H₄Cl (given kb = 1.8x10^-5 mol/L of NH₃)

  2. Find the pH of a solution with propionic acid at 0.10 mol/L and sodium propanoate at 0.05 mol/L (given ka = 1.34x10^-5 mol/L)
• Try these buffer calculations:

  1. Calculate the pH of a solution with 1 M HOAC and 1.0 M NaOAC (given ka = 1.8x10^-5)

  2. Find the pH of a buffer solution with 0.12 M benzoic acid and 0.20 M sodium benzoate (given ka = 6.3x10^-5)
• Blood as a buffered solution:

  • Human blood contains a buffer of carbonic acid (H₂CO₃) and bicarbonate anion (HCO₃⁻) to maintain pH between 7.35 and 7.45
  • Oxygen transport by hemoglobin (HbH⁺) affects blood pH
  • Buffer systems control blood pH during exercise and other conditions
• Effects of acidosis and alkalosis on blood pH:

  • Acidosis decreases ventilation rate and depth, lowering blood pH
  • Alkalosis increases ventilation rate and depth, raising blood pH
  • Alkalosis can lead to overstimulation of the nervous system and other symptoms
• Advantages of alkalosis:

  • Improved muscle function, blood flow, and oxygen delivery
  • Buffering lactic acid buildup during exercise
  • Enhanced nervous system activity and rapid reactions
• Treatment of acidosis and alkalosis:

  • Acidosis treatment depends on the cause, such as controlling blood sugar or improving lung function
  • Alkalosis treatment involves fluid and electrolyte balance and addressing the underlying cause of hyperventilation
• The brain is the only carbohydrate-dependent organ in the body
• The brain exclusively uses glucose, a basic simple sugar carbohydrate, to function
• Brain cells need twice the energy of any other cells in the body
• Some animal products contain carbs, such as lactose in milk and other dairy products
• Carbohydrates are the only fuel source metabolized fast enough to support hard exercise