The Human Body

• Levels of structural complexity

  • Atoms
  • Molecules & macromolecules
  • Organelle
  • Cell
  • Tissue
  • Organ
  • Organ system
  • Organism
• Atom


  Smallest particle of an element
• Molecule


  Particle of two or more atoms joined by chemical bonds
• Organelle


  Cellular structure that performs specific metabolic functions for the cell
• Cell


  Structural unit of all living things
• Cells are specialised to carry out particular functions, including essential life functions
• Tissue


  Group of cells that perform a specific function
• Organ


  Body part formed from >2 tissues that carry out a specific function
• Organ systems


  • Integumentary system
  • Skeletal system
  • Muscular system
  • Nervous system
  • Endocrine system
  • Cardiovascular system
  • Lymphatic system
  • Respiratory system
  • Digestive system
  • Urinary system
  • Reproductive system
• All body cells are interdependent and the functions of organ systems are functionally integrated to maintain life functions (homeostasis)
• Extracellular fluid (ECF)


  Fluid outside body cells
• Intracellular fluid (ICF)


  Fluid inside cells
• Body fluids (ECF, ICF) are solutions consisting of water (solvent) and solutes (electrolytes and non-electrolytes)
• Element


  Substance in which all the particles that make it up are exactly the same
• Major elements in the human body

  • Oxygen
  • Carbon
  • Hydrogen
  • Nitrogen
  • Calcium
  • Phosphorus
  • Potassium
  • Sulfur
  • Sodium
  • Chlorine
  • Magnesium
  • Iodine
  • Iron
• Atom


  Smallest stable unit of matter
• Molecule


  Particles formed by atoms combining via chemical bonds
• Cation


  Positively charged ion
• Anion


  Negatively charged ion
• Electrolyte


  Electrically charged atoms or molecules (ions) in solution
• Major electrolytes


  • Sodium
  • Potassium
  • Calcium
  • Hydrogen
  • Bicarbonate
  • Chloride
  • Phosphate
• pH scale


  Measure of the number of hydrogen ions (H+) in a solution
• Normal body pH range is 7.35-7.45
• Buffer


  Molecule that can bind or release free H+ ions to counter changes in pH and maintain normal pH range
• Organic molecule/compound


  Contains both carbon and hydrogen
• Inorganic molecule


  Does not contain both carbon and hydrogen
• Macromolecule


  Polymer - chain-like molecule made up of similar or repeating units called monomers
• Classes of organic macromolecules

  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic acids
• Monosaccharide


  Simple sugar or monomer
• Disaccharide


  Dimer (2 monomers)
• Polysaccharide


  Polymer of many monosaccharides
• Functions of carbohydrates


  • Provide energy for all cellular functions
  • Short term energy store
  • Minor function: building materials
• Monomers


  Units from which larger molecules are made
• 4 classes of organic macromolecules that make up our body

  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic acids
• Carbohydrates


  Include sugars (saccharides) and starches
• Carbohydrates


  Contain carbon, hydrogen and oxygen in the ratio CH2O e.g. glucose C6H12O6
• Types of carbohydrates


  • Monosaccharides (simple sugars or monomers, small, soluble, e.g. glucose)
  • Disaccharides (dimers, small, soluble, e.g. sucrose, lactose)
  • Polysaccharides (polymer of many monosaccharides, large, insoluble, e.g. glycogen)
• Carbohydrates


  • Major function: provide energy for all cellular functions
  • Short term energy store
  • Minor function: building materials
  • 1-2% of cell mass
  • Cell membrane receptors
  • Component of nucleic acids (DNA, RNA)
• Dietary sources of carbohydrates

  • Mono- and disaccharides - fruits, sugar cane, honey, milk
  • Polysaccharides - vegetables and grains
• Lipids


  Contain carbon, hydrogen and oxygen - the ratio of H:O is very high, e.g. cottonseed oil C57H110O6