Lecture 1 The Functions of Digestions

• Nutrition


  The science of how living organisms obtain and use food to support all the processes required for existence
• Food


  Provides your body, in particular your cells, with building materials and the resources it needs to carry out all functions
• Nutrients

  • Carbohydrates
  • Proteins
  • Lipids
  • Vitamins
  • Minerals
  • Water
• Micromolecules


  Small molecules that can pass easily through cell membranes and into your cells, do not need to be broken down before cells can absorb and utilise them
• Macromolecules


  Very large molecules (polymers) consisting of many smaller structural units (monomers) linked together, too big to pass through cell membranes and into your cells, must be broken down (disassembled) into smaller molecules before cells can absorb and utilise them
• Monomer


  Means 1
• Polymer


  Means multiple
• Carbohydrates and Proteins are true polymers because their monomers repeat, while Lipids' monomers are not repeating
• Dehydration synthesis (Condensation reaction)


  The chemical reaction responsible for the formation of macromolecules, involves the removal of water (H2O) for every monomer linked to another
• Types of Carbohydrates

  • Monosaccharides (simple sugars)
  • Disaccharides (double sugars)
  • Polysaccharides (complex sugars)
• Monosaccharides


  • Glucose
  • Fructose
  • Galactose
• Disaccharides


  • Sucrose (Table sugar)
  • Brown Sugar
• Polysaccharides


  • Cellulose
  • Glycogen
  • Starch
• Carbohydrates


  • Main source of energy
  • Quick energy from simple carbohydrates
  • Energy storage from complex carbohydrates
  • Structure - plant cell walls
• Only monosaccharides can be absorbed from the digestive system into the blood, and eventually into your body cells
• Lipids


  Macromolecules that do not dissolve in water, are all hydrophobic
• Lipid subcategories


  • Triglycerides
  • Phospholipids
  • Steroids
• Triglycerides


  Have three long hydrocarbon chains called fatty acids, all bonded to a glycerol group
• Saturated fatty acids


  Completely filled with hydrogen atoms
• Unsaturated fatty acids


  Have less hydrogen atoms and some double bonds
• Phospholipids


  Have a hydrophilic head with a phosphate, and two fatty acid chains that are hydrophobic
• Steroids


  Lipids that have 4 carbon rings, e.g. cholesterol, sex hormones
• Lipids


  • Structure - membranes
  • Protect vital organs
  • Hormones - steroids
  • Store energy
  • Insulate the body
• Unsaturated fats and some saturated fats are recommended in the diet, while trans fats should be limited due to increased risk of heart disease
• Proteins


  Chains (polymers) made up of over 20 different amino acid monomers
• Peptides, Polypeptides, Proteins


  Polymers of proteins named based on the number of amino acid subunits linked together
• Only amino acids can be absorbed from the digestive system into the blood, and eventually into your body cells
• Amino acid


  The monomer unit of a protein, has a central carbon surrounded by hydrogen, carboxyl group, amino group, and a side chain (R group)
• Protein structure


  • Primary - sequence of amino acids
  • Secondary - hydrogen bonding causing helical or pleated shape
  • Tertiary - further folding due to R-group interactions
  • Quaternary - interaction of 2+ polypeptide globules
• Protein functions


  • Growth and repair
  • Transport
  • Antibodies for immune system
  • Made up of amino acids, 8 are essential
• Minerals


  Inorganic nutrients needed to perform several different tasks/functions necessary for life
• Minerals

  • Calcium
  • Magnesium
  • Iron
  • Sodium
  • Iodine
  • Potassium
• Water


  Most important nutrient necessary for body cells to complete their cellular processes
• Functions of water

  • Makes up bulk of blood and other bodily fluids
  • Lubricates tissues and joints
  • Eliminates waste materials
  • Regulates body temperature
  • Transports dissolved nutrients