Biological Molecules

• Carbohydrates


  One of the main carbon based compounds in living organisms
• Carbohydrates


  • All molecules contain C, H or O
  • H and O are always present in a 2:1 ratio (e.g. H2O)
• Types of carbohydrates


  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Monosaccharide


  A single sugar, a monomer
• Disaccharide


  A sugar formed when 2 monosaccharides join together
• Polysaccharide


  A polymer formed from many monosaccharides
• Monosaccharides


  • Glucose
  • Fructose
  • Galactose
• Polysaccharides


  • Cellulose (b-glucose)
  • Starch (a-glucose in the form of amylose and amylopectin)
  • Glycogen (a-glucose)
• Glycosidic bond


  A bond formed between a carbohydrate molecule and any other molecule
• Monosaccharides


  • They are all reducing sugars
• Maltose


  A sugar found in germinating seeds
• Lactose


  A sugar found in mammal milk
• Sucrose


  A sugar stored in sugar cane
• Cellulose


  Strengthens the cell wall
• Starch and glycogen


  Energy storage molecules (in plants and animals respectively)
• Carbohydrates, proteins, lipids and nucleic acids are the key molecules required to form and build structures that enable organisms to function
• All four of these contain carbon and hydrogen which means that they are organic compounds
• Carbon atoms


  • Each can form 4 covalent bonds which makes the molecule very stable
  • Can form bonds with oxygen, nitrogen and sulfur
  • Are flexible and can bond to form straight chains, branched chains or rings
• Monomers


  Small single sub units that have the ability to bond with many repeating subunits to form polymers
• Polymers


  Bigger compounds formed via polymerisation (condensation reaction)
• Macromolecules


  Polymers that contain 1000 or more atoms
• Not all polymers are macromolecules, as the subunits of polymers have to be the same repeating units
• Covalent bond


  Sharing of 2 or more electrons between 2 different atoms
• Non-polar covalent bond


  Electrons are shared equally
• Polar covalent bond


  Electrons are shared unequally, resulting in one atom being more electronegative than the other
• Electronegativity


  The measure of the tendency of an atom to attract a pair of electrons available for bonding
• Covalent bonds


  Formed by sharing outer electrons, allowing atoms to fill their outer shell and gain stability
• Formation of covalent bonds

  1. Single bond

  2. Double bond

  3. Triple bond
• Dehydration synthesis


  Monomers combine to form polymers or macromolecules, with a H2O molecule removed
• Hydrolysis


  Breaking of covalent bonds by adding a H2O molecule
• Organic molecules


  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic Acids
• Glycoside


  Covalent bond between a carbohydrate and another molecule
• Peptide


  Covalent bond between amino acids
• Phosphodiester


  Covalent bond between nucleic acids
• Reducing sugar


  Can donate electrons, can be detected using Benedict's test
• Non-reducing sugar


  Cannot donate electrons, must be hydrolysed before Benedict's test
• Carbonyl group


  Carbon double bonded to oxygen, allows reducing sugars to be oxidised
• Glucose


  Most well-known carbohydrate, central to most life forms, exists in alpha and beta forms
• Steric effect


  Non-bonding interactions that influence the shape and reactivity of molecules, caused by repulsive forces between overlapping electron clouds
• Alpha glucose is less stable than beta glucose due to steric effect of hydroxyl group