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Chapter 1-5: Key Vocabulary from the Video Lecture on Chemistry and the Living Body

Bonding and Water in Biological Systems

  • Recap: Elements, atoms, and how they form bonds
  • Bonding types mentioned:
    • Sharing electrons (covalent bonding)
    • Trading/transferring electrons (ionic interactions)
    • Hydrogen bonding as a special interaction involving hydrogen between electronegative atoms (often O in water molecules)
  • Water molecule polarity:
    • Oxygen is partially negative; Hydrogen is partially positive
    • Opposite charges attract, leading to hydrogen bonds between water molecules
    • Each water molecule can attract and form bonds with about four others, promoting cohesion
  • Inorganic vs Organic molecules:
    • Inorganic: not living or not containing carbon; can be important to life
    • Organic: always associated with living systems; contain carbon; commonly include oxygen and hydrogen
  • Key takeaway about molecular composition in life: carbon-based chemistry underpins much of biology, with water as a central solvent and medium

Water as a Solvent, Transport Medium, and Cushion

  • Water as a transporter:
    • Blood is largely water; many substances dissolve in water for transport
    • Water enables dissolution and distribution of solutes throughout the body
  • Water as a solvent specific properties:
    • Polar nature makes it an excellent solvent for many substances
    • Lipids (oils, fats) do not dissolve well in water, leading to separation unless transported by binding proteins
  • Water’s lubricating and cushioning roles:
    • Cerebrospinal fluid surrounds brain and spinal cord providing cushioning
  • Water and waste excretion:
    • Water aids in excretion; kidneys and urinary system rely on water to flush waste
  • Homeostatic importance of water:
    • Adequate water intake helps regulate body temperature via mechanisms like sweating
    • Dehydration can lead to elevated body temperature due to impaired thermoregulation
  • Water properties related to temperature:
    • High specific heat helps stabilize body temperature during environmental changes
  • Lipid transport context:
    • Some substances (hormones, vitamins) are fat-soluble and do not dissolve well in water
    • The body uses proteins to bind and transport lipid-soluble substances through the bloodstream
  • Hydrophobic vs hydrophilic concepts:
    • Water tends to separate hydrophobic (lipid) from hydrophilic substances unless emulsified or bound to carrier molecules

pH, Acids, Bases, and Buffers

  • Water autoprotolysis (dissociation):
    • ext{H}_2 ext{O}
      ightleftharpoons ext{H}^+ + ext{OH}^-
    • Often written with hydronium: ext{H}2 ext{O} + ext{H}2 ext{O}
      ightleftharpoons ext{H}_3 ext{O}^+ + ext{OH}^-
  • The pH scale:
    • Ranges from 0 to 14; 7 is neutral
    • Definition: ext{pH} = -
      abla_{10}[ ext{H}^+]
    • At 25°C, pure water has [ ext{H}^+] = [ ext{OH}^-] = 1.0 imes 10^{-7} ext{ M}, giving pH = 7
  • Logarithmic nature of pH:
    • A change of one pH unit represents a tenfold change in hydrogen ion concentration
    • Example: moving from pH 6 to pH 7 changes
      [ ext{H}^+] ext{ from } 1.0 imes 10^{-6} ext{ M to } 1.0 imes 10^{-7} ext{ M}, a tenfold decrease
  • Acids and bases in the body:
    • Strong acid/base examples and pH implications discussed; a strong base like sodium hydroxide can reach pH 14
  • Buffer systems (homeostasis):
    • Body uses buffers to prevent rapid pH shifts in blood and body fluids
    • Buffers help maintain pH within a narrow physiological range important for enzyme activity and metabolism
  • Stomach acid and tissue protection:
    • Hydrochloric acid (
      ext{HCl}) in the stomach aids digestion
    • Stomach lining has specialized tissues to resist self-digestion, but reflux or ulcers can burn tissue (e.g., esophagus or ulcers in stomach)
  • Implications of pH balance:
    • Large, rapid pH shifts can be harmful; buffers and regulatory mechanisms are essential for maintaining homeostasis

Mixtures, Emulsions, and Samples in Biology

  • Emulsions:
    • Emulsion: forcing two immiscible liquids to mix using energy or emulsifiers
    • Mayonnaise as a classic example: fats/oils emulsified with water and egg proteins
    • Emulsions require mechanical mixing or emulsifying agents; without mixing they can separate over time
  • Suspensions vs solutions:
    • Sand-in-water as an example of a suspension: large particles settle out over time
    • In solutions, solutes are dissolved and not visible; in suspensions they remain dispersed but settle
  • Blood as a suspension:
    • Blood contains cells and other components that appear uniform in motion but separate under centrifugation
    • Dense components (cells, nucleic acids, lipids) settle out when spun down; the serum/plasma remains above
  • Practical implications:
    • Understanding phases helps in interpreting lab samples, centrifugation results, and the behavior of lipids, proteins, and other macromolecules in fluids

The Four Major Biomacromolecule Groups

  • Four main macromolecules in animals and many organisms: carbohydrates, proteins, lipids, nucleic acids
  • Macromolecule definition:
    • Large molecules formed when smaller units bond together (polymers from monomers)
  • Common elements in biomolecules:
    • Hydrogen (H), Carbon (C), Oxygen (O), Nitrogen (N), Phosphate (P, in nucleic acids)
  • Carbohydrates:
    • Provide quick energy and serve as energy storage
    • Built from monosaccharides; examples include glucose, starches, glycogen, and cellulose (in plants)
  • Proteins:
    • Built from amino acids
    • Structural roles (nails, hair, skin) and functional roles (enzymes, transport, signaling, immune)
    • Meat (e.g., chicken, steak, seafood) is a source of dietary protein; digestion provides amino acids for body protein synthesis
  • Lipids:
    • Include fats, waxes, and phospholipids; often contain carbon, hydrogen, and oxygen (some nitrogen in certain lipids)
    • Not always a true macromolecule in strict chemistry terms, but biochemically grouped with macromolecules
    • Hydrophobic; essential for energy storage, membranes, and signaling; transport via lipid-binding proteins and lipoproteins
  • Nucleic acids:
    • DNA and RNA; store and transfer genetic information; monomers are nucleotides
  • Interconnectedness and function:
    • These macromolecules form the basis of cellular structure and function; nutrients from the diet support macromolecule synthesis and maintenance
  • Note on source and metabolism:
    • Nutritional intake (e.g., proteins from meat) provides amino acids that the body uses to synthesize its own proteins, including structural and functional proteins
  • Page 44 reference (textbook or slide): water properties, transport, and organ system relevance
  • Practical relevance:
    • Water balance, pH maintenance, and macromolecule synthesis are foundational for physiology, biochemistry, and health science careers
    • Understanding emulsions, suspensions, and solubility helps interpret lab results and physiological processes (e.g., lipid transport, protein binding, and blood composition)