Monomers and polymers and carbohydrates

• Define monomer. Give examples

  ~Smaller units that join together to form larger molecules

  ~Monosaccharides

  ~Amino acids

  ~Nucleotides
• Define polymer. Give examples

  ~Molecules formed when many monomers join together

  ~Polysaccharides

  ~Proteins

  ~DNA/RNA
• What happens in a condensation reaction


  A chemical bond forms between two molecules and a molecule of water is produced
• What happens in a hydrolysis reaction

  A water molecules is used to break a chemical bond between two molecules
• Name the three hexose monosaccharides

  ~Glucose

  ~Fructose

  ~Galactose
• Name three disaccharides

  ~Glucose + glucose = maltose

  ~Glucose + fructose = sucrose

  ~Glucose + galactose = lactose
• Describe the structure and functions of starch

  ~Storage polymer of alpha glucose in plant cells

  ~Insoluble so no osmotic effect on cells

  ~Made from amylose or amylopectin
• Describe the structure and functions of glycogen

  ~Main storage polymer of alpha glucose in animal cells

  ~Branched = many terminal ends for hydrolysis

  ~Insoluble = no osmotic effect and does not diffuse out of cells

  ~Compact
• Describe the structure and functions of cellulose

  ~Polymer of beta glucose gives rigidity to plant cell walls

  ~Straight and unbranched molecule

  ~H-bond crosslinks between parallel strands form microfibrils
• Describe the benedicts test for reducing sugars

  ~Add an equal volume of Benedicts reagent to a sample

  ~Heat the mixture in an electric water bath at 100°c for five minutes

  ~Positive result = colour change from blue to orange and brick red precipitate forms
• Describe the benedicts test for non-reducing sugars

  ~Negative result means benedicts reagent remains blue

  ~Hydrolyse non-reducing sugars into their monomers by adding 1cm³ of HCl. Heat in a boiling water bath for five minutes

  ~Neutralise the mixture using sodium carbonate solution

  ~Proceed with the benedicts test as usual
• Describe the test for starch

  ~Add iodine solution

  ~Positive result = colour change from orange to blue - black
• Outline how colorimetry could be used to give qualitative results for the presence of sugars and starch

  ~Make standard solutions with known concentrations. Record absorbance or % transmission values

  ~Plot calibration curve: absorbance or % transmission and concentration

  ~Record absorbance or % transmission values of unknown samples. Use calibration curve to read off concentration