The chemistry of life and human digestion

• Cells


  • The smallest unit of life, contains cell inclusions, i.e. organelles
• Tissues


  • A group of similarly differentiated cells that perform a common function
• Organs


  • A group of different tissues, which each performs its own function, but also perform a common function as a group
• Organ systems


  • Group of organs working together for a specific function
• Organism


  A living entity consisting of organ systems
• Chemical compounds


  • Organic compounds
  • Inorganic compounds
• Organic compounds


  Contain the element CARBON and are produced by living organisms
• Organic compounds


  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic acids
  • Vitamins
• Inorganic compounds


  Do not contain the element carbon and are not produced by living organisms
• Inorganic compounds


  • Water
  • Mineral Salts
• What is needed for a balanced diet

  • Carbohydrates
  • Lipids
  • Proteins
  • Vitamins
  • Minerals
• All of these can only be absorbed in the human body in their simplest form (monomer)
• For absorption in the human body, we need enzymes and components must be soluble in water
• Carbohydrates


  Consist of the elements C, H and O, with a ratio of H-atoms to O-atoms of 2:1
• Glucose


  The monomer of carbohydrates
• Carbohydrates


  • Sugars and starch (energy sources)
  • Structural component of cell wall
• Carbohydrate molecules


  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Glucose + Glucose


  Maltose + H₂O
• Glucose + Galactose


  Lactose + H₂O
• Monosaccharides


  Single sugars with a sweet taste
• Monosaccharides


  • Triose (3C, pyruvate)
  • Hexose (6C sugars: Glucose, Fructose, Galactose)
• Disaccharides


  Double sugars formed when two monosaccharides combine with each other
• Disaccharides


  • Maltose (malt sugar)
  • Sucrose (cane sugar)
  • Lactose (milk sugar)
• Polysaccharides


  Long chains of monosaccharides joined together
• Polysaccharides


  • Starch (stored in plants)
  • Glycogen (stored in humans)
  • Cellulose (structural component of plant cell walls)
  • Chitin (structural component of insect exoskeletons and fungal cell walls)
• Starch


  • The form in which carbohydrates are stored in plants
• Glycogen


  • The form in which carbohydrates are stored in humans
• Cellulose


  • Forms a structural component of cell walls in plant cells
• Chitin


  • Substance found in the exoskeleton of insects as well as the cell walls of fungi
• The building blocks of starch, glycogen and cellulose are glucose, however the way they are bound together differs
• Importance of carbohydrates


  • Source of energy
  • Structural component
• Glucose


  The most important fuel molecule
• During cellular respiration, energy is released from glucose while CO₂ and H₂O are formed
• Starch and glycogen are stored in plants and animals respectively, and are insoluble in water so they do not influence the water potential of the cells
• Cellulose strengthens the cell walls of plant cells
• Chitin gives support and strength to exoskeletons and cell walls of fungi
• Lipids (fats & oils)

  Consist of the elements C, H and O (same as carbohydrates), but have a ratio of H:O greater than 2:1
• Fat molecule


  Consists of 1 glycerol molecule and 3 fatty acid chains
• Importance of fats & oils

  • Source of energy (supply 10 times more energy than carbohydrates)
  • Insulation
  • Production of steroid hormones
• Excess fats from absorption form adipose tissue