The chemical level of organisation

• Ionic Bonds


  Ions are typically found in solutions, attracted by charge, remove the water and they join together forming crystals, some dissolve easily in water some do not
• Hydrogen bonds


  Formed between charged ends of adjacent polar molecules and/or ions, most common in (liquid) water
• Atomic structure


  Atoms have a nucleus with protons and neutrons, and electron shells with groups of electrons making up stable shells (generally 2 or 8 electrons)
• Chemical bonds

  • Ionic (strong attraction between ions)
  • Covalent (medium attraction–electron sharing)
  • Hydrogen (weak bonds)
• Levels of organisation

  • Organism
  • Organ system
  • Tissue
  • Cellular
  • Chemical/molecular
• Covalent


  Additionally, the shared electrons may be: Equal bonds (balanced charge) non-polar, Unequal bonds (unbalanced charge) polar
• Ions(cations and anions)


  1. Cation: When electrons are lost, forming a positive ion

  2. Anion: When electrons are gained, forming a negative ion

  3. Ionic elements are attracted to opposite charge, some form stable compounds (e.g. NaCl common salt)
• Covalent bonds


  Completion of outer shell electrons by sharing with other atoms, 1 pair shared is a single bond (e.g. hydrogen), 2 pairs shared is a double bond (e.g. oxygen)
• Hydrogen bonds


  • Formed between charged ends of adjacent polar molecules and/or ions
  • Most common in (liquid) water
• Water

  • Approximately 2/3 of body weight with special properties: Solubility, Reactivity, High heat capacity, Lubrication
• Salts & Buffers


  • Salt: Ionic compound of any cation and any anion (but not H+ and OH–). Many salts dissociate in water. Buffer: Absorb or release ions to keep pH stable. Typically in a physiological system remove or replace hydrogen ions
• Shared electrons

  • Equal bonds (balanced charge) are non-polar
  • Unequal bonds (unbalanced charge) are polar
• Organic compounds

  • Glucose, Lipid
• Inorganic compounds

  • Water
  • Solutes
  • Hydrogen ions
  • Acid/base
  • Salts
• pH

  • 7 neutral (equal hydrogen and hydroxyl ions)
  • pH <7 acidic (more hydrogen than hydroxyl ions)
  • pH >7 basic (more hydroxyl than hydrogen ions)
• Electrolysis (splitting water)


  Requires a lot of energy, from 2 molecules of water produces: 2 molecules of hydrogen gas (H2) and 1 molecule of oxygen gas (O2)
• Organic compounds

  • Carbohydrates, Lipids, Proteins, Nucleic acids
• Buffers

  • Buffers absorb or release ions to keep pH stable. Important for physiological systems to remove or replace hydrogen ions.
  • They help maintain the intracellular and extracellular pH within a narrow range and resist changes in pH in the presence of internal and external influences.
• pH importance

  pH is crucial as all biological processes are dependent on it. Cells and organisms must maintain a specific pH so their enzymes are in optimum state of protonation (providing atom, molecule or ion with a proton).