Topic 1

• Monomer definition


  One of many small molecules that combine to form a larger one known as a polymer
• Poylmer definition


  Large molecule made up of repeating smaller molecules
• Condensation reaction


  When two molecules join together with the formation of a new chemical bond, and a water molecule is released when the bond is formed
• Hydrolysis reaction


  The breaking down of large molecules into smaller ones by the addition of water molecule
• What elements are carbohydrates made from?

  Carbon, hydrogen and oxygen
• Monosaccharide definition


  A monomer of carbohydrates
• Disaccharide definition


  A molecule that is made up of two monosaccharides
• Polysaccharide definition


  A molecule formed from more than two monosaccharides
• What type of sugar is glucose?

  Hexose sugar
• Isomer definition


  Two molecules with the same molecular formula as each other, but with the atoms connected in a different way
• Draw the structure of alpha glucose

  
• Draw the structure of beta glucose

  
• What type of bond forms between monosaccharides?

  Glycosidic bond
• What is maltose made up of?

  Glucose + glucose
• What is sucrose made up of?

  Fructose + glucose
• What is lactose made up of?

  Glucose + galactose
• Structure of starch


  Alpha glucose molecules joined together to form a helix resulting in a large compact molecule
• Function of starch


  Store of excess glucose in plants
• Linking the structure of starch to its function (3)

  1. Helix makes it compact so a lot of glucose can be stored in a small space

  2. Large size means it is insoluble so does not affect the water potential of cells

  3. Large size so unable to move out of cells
• Structure of glycogen


  Polysaccharide of alpha glucose molecules, joined together by glycosidic bonds to form a helix resulting in a large compact molecule that is more branched than starch
• Function of glycogen


  Store of excess glucose in animals
• Linking the structure of glycogen to its function (3)

  1. Helix makes it compact so a lot of glucose can be stored in a small space

  2. Large size means it is insoluble so does not affect the water potential of cells

  3. Many branches mean more ends so it is easily hydrolysed to release glucose for respiration
• Structure of cellulose


  Beta glucose molecules joined together to form long unbranched chains. Hydrogen bonds between chains allow them to form microfibrils
• Function of cellulose


  To provide structural support, for example in plant cell walls
• Linking the structure of cellulose to its function


  The hydrogen bonds ensure the microbrils are strong and stable giving strength and rigidity to the plant cell wall. This prevents the cells bursting when water enters by osmosis so they become turgid
• Test for sugars


  Benedict's test
• Process of testing for non-reducing sugars

  Take a second sample and add it to 2cm3 of water in a test tube. Add 2cm3 of dilute hydrochloric acid and place in a boiling water bath for 5 minutes. Add sodium hydrogen carbonate to neutralise. Re-test the solution by heating with 2cm3 of Benedict's reagant ina boiling water bath for 5 minutes
• Process of testing for reducing sugars

  Add the food sample to 2cm3 of water in a test tube and add an equal amount of Benedict's reagant. Heat the mixture in a boiling water bath for 5 minutes
• What would a positive/negative result look like when testing for sugars?

  Positive result: sample forms green/yellow/orange/brick red precipitate depending on the amount of sugar

  Negative result: sample stays blue
• Test for starch


  Iodine solution
• Process of testing for starch


  Place a small quantity of the sample being tested into a test tube and add one or two drops of potassium iodide solution
• What would a positive/negative result look like when testing for starch?

  Positive result: the sample turns dark blue/black

  Negative result: the solution will stay browny orange
• What elements are lipids made from?

  Carbon, hydrogen and oxygen
• How are lipids different to carbohydrates and proteins?

  They can't form polymers as they don't have monomers
• Describe the structure of a triglyceride

  One molecule of glycerol and three fatty acids
• Draw the structure of a triglyceride

  
• What are fatty acid tails made from and what property do they have?

  Hydrocarbons - they are hydrophobic
• How are triglycerides formed?

  By a condensation reaction between fatty acids and a glycerol. An ester bond is formed and a molecule of water is removed
• Difference between a saturated an unsaturated fatty acid

  Saturated fatty acids don't have any double bonds between their carbon atoms while a unsaturated does
• 5 functions of a tryglyceride


  Source of energy, waterproofing, insulation, protection, buoyancy