Food - Biology

• Function of Food


  • Source of energy
  • To make chemicals for metabolism
  • For growth and repair
• Common elements found in all foods


  • Carbon
  • Hydrogen
  • Oxygen
  • Sulfur
  • Nitrogen
• Common elements found in salts


  • Sodium
  • Magnesium
  • Chlorine
  • Potassium
  • Iron
  • Copper
  • Zinc
• Carbohydrates


  Consist of elements: carbon, hydrogen and oxygen
• Types of carbohydrate


  • Monosaccharide (Smallest, one sugar unit e.g. glucose, fructose)
  • Disaccharide (Two monosaccharides connected e.g. maltose, lactose)
  • Polysaccharide (Largest, many monosaccharides connected e.g. starch, cellulose, glycogen)
• Starch


  • Found in ground tissue of plants
• Cellulose


  • Found in plant cell walls
• Glycogen


  • Found in the liver
• Reducing sugars


  All monosaccharides and some disaccharides
• Carbohydrate ratio


  Ratio of hydrogen to oxygen is 2:1, General formula: Cx(H2O)y
• Lipids


  Consist of oils, fats and steroids
• Oils


  Liquids at room temperature
• Fats


  Solid at room temperature
• Lipids


  • Contain the elements carbon, hydrogen and oxygen
• Functions of Fat


  • Heat insulation
  • Energy store
• Phospholipids


  One glycerol, two fatty acids, one phosphate head, found in cell membranes

  
• Triglyceride


  One glycerol, three fatty acids, found in fatty foods

  
• Proteins


  Contain the elements carbon, hydrogen, oxygen and nitrogen, sometimes contain sulfur
• Amino acid


  The smallest unit of a protein
• There are 20 common amino acids found in proteins
• Peptide bond


  The bond between amino acids
• Protein types


  • Structural (fibrous) protein (e.g. keratin in hair, nails)
  • Metabolic protein (e.g. enzymes, hormones)
• Sources of protein


  • Lean meat
  • Fish
  • Egg white
• Vitamins


  Required in only small amounts in the diet for health, cell production and tissue growth
• Water-soluble Vitamin: Vitamin C


  Found in citrus fruits, deficiency causes scurvy
• Fat-soluble Vitamin: Vitamin D


  Found in milk, eggs, sunshine, deficiency causes rickets
• Minerals


  Required in tiny amounts by organisms
• Calcium (Ca) for plants


  Helps cell walls to attach to one another, source is the soil
• Magnesium (Mg) for plants


  Needed for chlorophyll production, source is the soil
• Calcium (Ca) for animals


  Needed for the formation of teeth and bones, source is milk and cheese
• Iron (Fe) for animals


  Needed for the formation of haemoglobin to help transport oxygen, source is meat and green vegetables
• Water


  A component of cytoplasm and body fluids (70-95% of cell mass), a solvent and medium in which chemical reactions take place
• Metabolism


  The sum of all the chemical reactions in an organism
• Anabolic reactions


  Formation of large complex molecules from smaller molecules, requires energy (e.g. photosynthesis)
• Catabolism


  Breakdown of large molecules into smaller molecules, releases energy (e.g. respiration)