Nature of Molecules

• Matter


  Anything that occupies space & has mass
• Living things


  • Take up space and has mass
• Phases of matter


  • Solids
  • Gases
  • Liquids
• Matter is made up of elements - in pure form & in combinations
• 92 elements occur naturally on Earth
• About 25 chemical elements make up life
• Element


  A substance that cannot be broken down to other substances by chemical reactions
• Compound


  A substance consisting of two or more elements in a fixed ratio
• Properties of an element

  • Depend on the structure of its atoms
  • Each element consists of unique atoms
• Subatomic particles


  • Neutrons (no electrical charge)
  • Protons (positive charge)
  • Electrons (negative charge)
• Neutrons and protons form the atomic nucleus

  
• Electrons form a cloud around the nucleus
• Neutron mass and proton mass are almost identical and are measured in Daltons

  
• Atomic number

  Number of protons

  
• Mass number


  Protons + neutrons

  
• Isotopes


  Two or more atoms of an element that differ in number of neutrons

  
• Radioactive isotopes


  Unstable nuclei that dissipate excess energy by spontaneously emitting radiation
• Applications of radioactive isotopes in biological research

  • Dating fossils
  • Tracing atoms through metabolic processes
  • Diagnosing medical disorders
• Energy


  The capacity to cause change
• Potential energy


  The energy that matter has because of its location or structure
• Energy level


  An electron's state of potential energy
• Chemical behavior is determined by the number & arrangement of its electrons in their orbitals

  
• Orbital


  The three-dimensional space where an electron is found 90% of the time
• Each electron shell consists of a specific number of orbitals
• Valence electrons


  Those in the outermost shell, or valence shell
• The chemical behavior of an atom is mostly determined by the valence electrons
• Elements with a full valence shell are chemically inert
• Essential elements of life

  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
  • Calcium
  • Phosphorus
  • Potassium
  • Sulfur
• Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter
• Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur
• Trace elements


  Those required by an organism in minute quantities
• Carbon


  • Structural: Forms backbone / framework of organic molecules
• Hydrogen


  • Physiological /Metabolic role: Hydrogen ions are used to regulate physiological pH, Hydrogen ions are used in cellular active transport
  • Structural: Component organic molecules

  
• Oxygen


  • Metabolic: Used as the final electron acceptor during cellular respiration, Used to break a phosphate from ATP to release energy in tissues
  • Structural: Component of organic molecules
• Nitrogen


  • Structural: Forms part of haemoglobin (rbc protein) which transports oxygen, and myoglobin which stores oxygen in muscles, Component of ferredoxin (chloroplasts protein), which is an electron acceptor during photosynthesis
  • Metabolic: Used for the synthesis of amino acids, Synthesis of chlorophyll in plants

  
• Phosphorus


  • Structural: Phospholipids (plasma membranes) are components give the cell membrane its fundamental characteristics (semipermeability), Together with sugar molecules, phosphates form the backbone of DNA and RNA, Teeth and bones, as well as cartilage and sinew, obtain their hardness and strength from calcium phosphate
  • Metabolic: The role of phosphate in ATP is to transport energy to create energy-rich bindings
• Some naturally occurring elements are toxic e.g. arsenic
• Some species are adapted to environments containing toxic elements e.g. serpentine-tolerant species
• Serpentine


  Mineral containing nickel, cobalt & chromium
• Hyperaccumulation


  Adaptation to environments containing toxic elements