biological molecules

• The energy stored in biological molecules, such as carbohydrates, proteins and fats, are required by living organisms to carry out life processes and maintain health
• Why do we need food?

  The nutrients in food provide us with energy and materials needed by the body
• Types of Nutrients


  • Carbohydrates
  • Fats
  • Proteins
• Biological molecules


  Substances that produced by cells and living organisms, such as carbohydrates, proteins and fats. All biological molecules are large molecules built from smaller basic units
• Monomers


  Basic building blocks, repeating units make up the biomolecules
• Polymers


  The whole biomolecule (made of monomers)
• Carbohydrates


  Organic molecules made up of Carbon, Hydrogen and Oxygen. The Hydrogen and Oxygen atoms are present in the ratio of 2:1. The general formula is CnH2mOm
• Carbohydrate classifications


  • Single sugars
  • Double sugars
  • Complex carbohydrates
• Carbohydrates


  • Substrate for respiration - provide energy for cell activities
  • Form supporting structures - e.g. plant cell walls
  • Form nucleic acids, e.g. DNA, RNA
  • Synthesise lubricants - e.g. mucus: glycoprotein
  • Synthesise nectar in some flowers
• Monosaccharides


  Carbohydrates that cannot be broken down further into simpler forms. Examples: glucose, fructose, galactose
• Disaccharides


  Created when 2 monosaccharides become linked through a condensation reaction. Examples: maltose, lactose, sucrose
• Complex carbohydrates


  • Starch - storage form in mammals
  • Glycogen - storage form in plants
  • Cellulose - cell wall protects plant cells, serve as dietary fibres
• Why are glycogen and starch used as storage materials?
• Hydrolysis of starch


  1. Starch is broken down into maltose molecules by amylase

  2. Maltose molecules are broken down into glucose by maltase
• The purpose of conducting food tests is to find out what nutrient is present in an unknown sample
• Reducing sugars


  Sugars with a free aldehyde or ketone group that can reduce other substances. Examples: monosaccharides and some disaccharides
• Benedict's test for reducing sugars


  Add Benedict's solution to food sample, shake, heat in boiling water bath for 2-3 minutes
• Proteins are organic molecules made up of carbon, hydrogen, oxygen and nitrogen
• Amino acids


  The smaller basic units that make up proteins
• Protein structure


  • Amino acids are linked by peptide bonds to form a polypeptide
  • Two or more polypeptide chains fold to form a 3-D protein molecule
  • Amount, type and arrangement of amino acids affects protein properties
• Denaturation of proteins


  Under certain conditions like heat or change in pH, the unique 3D shape of proteins can be changed, causing the protein to lose its ability to function
• Functions of proteins


  • Synthesis of protoplasm for growth and repair
  • Enzymes are protein in nature
  • Some hormones are made of protein
  • Antibodies and blood clotting factors
  • Source of energy during extreme starvation
• Biuret test for proteins

  Add biuret solution to food sample, shake, allow to stand for 5 minutes
• Fats


  Organic molecules made up of carbon, hydrogen and oxygen. Contain much less oxygen in proportion to hydrogen
• Fats


  • Commonly used as a store of energy, especially by animals
  • Made from fatty acids and glycerol in a condensation reaction
  • Broken down to fatty acids and glycerol by lipase
• Functions of fats


  • As an energy source and a long-term storage of energy
  • Insulating material- prevents excessive heat loss
  • Solvent for fat-soluble vitamins and hormones
  • Form cell membranes
  • Oily substance secreted by glands in the skin - reduce evaporation and rate of heat loss from skin surface
• Types of fats


  • Saturated and unsaturated
  • Trans fats
  • Cholesterol
  • High density lipids (HDL) and low density lipids (LDL)
• Ethanol emulsion test for fats

  Add ethanol to food sample, shake, decant into water and shake
• If starch is represented by this molecule, a fat molecule and a protein molecule (small section of 5 units) would look like...
• Malnutrition is due to dietary imbalance and can lead to effects like obesity, coronary heart disease, starvation, deficiency diseases, constipation, and cancers
• Glucose


  A simple sugar that can be absorbed and used for energy by the body
• Maltase


  An enzyme that breaks down maltose into individual glucose molecules
• Maltose


  A disaccharide made up of two glucose molecules
• Amylase


  An enzyme that breaks down starch into maltose