WATER AND BUFFER (BIOMOLECULES)

• Water and Buffer Outline

  1. Anatomy and Physiology (Inorganic Compounds Essential to Human Functioning)

  2. Hydrogen Bonding and Water

  3. Other Bonds and Solvation

  4. Hydrophobic Effect and Its Consequences

  5. Acids, Bases, and pH

  6. Henderson-Hasselbalch

  7. Polyprotic Acids and Protonation State

  8. Aqueous Buffers

  9. Homeostasis

  10. Water and Buffer 1 of 3

  11. Water and Buffer 2 of 3

  12. Water and Buffer 3 of 3

  13. References
• Inorganic compound


  • Does not contain both carbon and hydrogen
• Inorganic compounds containing hydrogen atoms

  • Water (H2O)
  • Hydrochloric acid (HCl)
• Inorganic compounds containing carbon atoms

  • Carbon dioxide (CO2)
• Organic compound


  • Contains both carbon and hydrogen
• Organic compounds


  • Synthesized via covalent bonds within living organisms, including the human body
• Carbon and hydrogen are the second and third most abundant elements in the body
• As much as 70 percent of an adult’s body weight is water
• Water as a Lubricant and Cushion


  • Water in synovial fluid lubricates body joints
  • Water in pleural fluid helps lungs expand and recoil
  • Watery fluids help keep food flowing through the digestive tract
  • Water protects cells and organs from physical trauma
  • Water cushions a developing fetus in the mother’s womb
• Water as a Heat sink


  • Water absorbs heat generated by chemical reactions
  • Water helps keep the body cool in high environmental temperatures
• Water as a Component of Liquid Mixtures

  • Water is polar and readily dissolves ionic compounds and polar covalent compounds
  • Sugar dissolves well in water due to hydrogen-oxygen polar bonds making it hydrophilic
• Water


  Polar, with regions of positive and negative electrical charge, readily dissolves ionic compounds and polar covalent compounds
• Sugar


  Dissolves well in water due to containing regions of hydrogen-oxygen polar bonds, making it hydrophilic (water-loving)
• For cells in the body to survive, they must be kept moist in a water-based liquid called a solution
• Concentration of solute


  The number of particles of a given solute in a given space
• In the bloodstream of humans, glucose concentration is usually measured in milligrams per deciliter (mg/dL) and in a healthy adult averages about 100 mg/dL
• Measuring concentration of a solute

  By molarity (moles of the molecules per liter) or by the number of particles in a given space
• Colloid


  A mixture somewhat like a heavy solution
• Suspension


  A liquid mixture in which a heavier substance is suspended temporarily in a liquid, but over time, settles out
• Chemical reactions involving water

  Dehydration synthesis and hydrolysis
• Dehydration synthesis


  One reactant gives up an atom of hydrogen and another reactant gives up a hydroxyl group in the synthesis of a new product, releasing a molecule of water as a byproduct
• Hydrolysis


  A molecule of water disrupts a compound, breaking its bonds, with the water splitting into H and OH, bonding with different portions of the compound
• A typical salt, NaCl, dissociates completely in water
• Many other salts are important in the body, such as bile salts aiding in breaking apart dietary fats and calcium phosphate salts forming the mineral portion of teeth and bones
• Acids


  Substances that release hydrogen ions (H+) in solution
• Bases


  Substances that release hydroxyl ions (OH-) in solution or accept H+ already present in solution
• Strong acids release all of their H+ in solution, while weak acids do not ionize completely
• Bases


  1. A base is a substance that releases hydroxyl ions (OH–) in solution, or one that accepts H+ already present in solution

  2. The hydroxyl ions (also known as hydroxide ions) or other basic substances combine with H+ present to form a water molecule, thereby removing H+ and reducing the solution’s acidity

  3. Strong bases release most or all of their hydroxyl ions

  4. Weak bases release only some hydroxyl ions or absorb only a few H+

  5. Bicarbonate accepts some of the H+ protons, thereby reducing the acidity of the solution
• pH


  • The negative, base-10 logarithm of the hydrogen ion (H+) concentration of the solution
  • A solution with a pH of 7 is considered neutral—neither acidic nor basic
  • Pure water has a pH of 7
  • The lower the number below 7, the more acidic the solution, or the greater the concentration of H+
  • The concentration of hydrogen ions at each pH value is 10 times different than the next pH
  • The higher the number above 7, the more basic (alkaline) the solution, or the lower the concentration of H+
  • Human urine is ten times more acidic than pure water, and HCl is 10,000,000 times more acidic than water
• The pH of human blood normally ranges from 7.35 to 7.45, although it is typically identified as pH 7.4
• At a slightly basic pH, blood can reduce the acidity resulting from the carbon dioxide (CO2) constantly being released into the bloodstream


  Homeostatic mechanisms normally keep the pH of blood within a narrow range
• All cells of the body depend on homeostatic regulation of acid–base balance at a pH of approximately 7.4
• Buffers


  • A buffer is a solution of a weak acid and its conjugate base
  • A buffer can neutralize small amounts of acids or bases in body fluids
• Water is abundant in living organisms
• Water is composed of 2 H atoms covalently bonded to 1 O atom
• Hydrogen bonds


  • Water is polar
  • The atoms have dipoles: partial charges
  • Due to unequal sharing of electrons, water is polar with oxygen carrying a partial negative dipole and hydrogen atoms carrying a partial positive charge
  • Dipoles can align to form hydrogen bonds with some covalent character
• Unequal sharing of electrons

  Oxygen is more electronegative and holds on to more electrons, resulting in a partial positive charge on hydrogen atoms
• Dioles


  • Can align to form H bond
  • Has some covalent character (directionality)
• Formation of stronger vs. weaker H-bonds

  1. Linear alignment is stronger, allowing for maximum overlap of orbitals and shortest distance for strongest bond

  2. Confers geometric constraints
• Properties of Water


  • Highly cohesive
  • Liquid at room temperature
  • High surface tension
  • Solid less dense than liquid
  • Expands as it solidifies
  • Ice floats