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Organic macromolecules


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Organic macromolecules

  1. 1. 12. Organic macromolecules Chemistry Grade 12Everything Science
  2. 2. 2Introduction A polymer is a macromolecule that is made up of many repeating structural units calledmonomers which are joined by covalent bonds. Polymers that contain carbon atoms in the main chain are called organic polymers. Organic polymers can be divided into natural organic polymers (e.g. natural rubber) orsynthetic organic polymers (e.g. polystyrene).The polymer polyethene for example, is made up of many ethene monomers that havebeen joined into a polymer chain. Everything Science
  3. 3. 3PolymerisationPolymers form through a process called polymerisation.Two examples of polymerisation reactions are addition and condensation reactions.An addition reaction occurs when unsaturated monomers (e.g. alkenes) are added to eachother one by one. The breaking of a double bond between carbon atoms in the monomer,means that a bond can form with the next monomer. The polymer polyethene is formedthrough an addition reaction.In a condensation reaction, a molecule of water is released as a product of the reaction. Thewater molecule is made up of atoms that have been lost from each of the monomers.Polyesters and nylon are polymers that are produced through a condensation reaction. Everything Science
  4. 4. 4Properties of polymersThe chemical properties of polymers (e.g. tensile strength and melting point) aredetermined by the types of atoms in the polymer, and by the strength of the bondsbetween adjacent polymer chains. The stronger the bonds, the greater the strength of thepolymer, and the higher its melting point.Some examples are: Hydrogen bondsPolymers that contain amide or carbonyl groups can form hydrogen bonds betweenadjacent chains. Polymers that contain hydrogen bonds have high tensile strength and ahigh melting point. Dipole-dipole forcesPolyesters have dipole-dipole bonding between their polymer chains. Dipole bonding isnot as strong as hydrogen bonding, so a polyester’s melting point and strength are lowerthan those of the polymers where there are hydrogen bonds between the chains. Thesepolymers have greater flexibility. van der Waals forcesThese polymers have a low melting point. Everything Science
  5. 5. 5PlasticsOne group of synthetic organic polymers, are the plastics.Some types are: Polystyrene is a plastic that is made up of styrene monomers. Polystyrene is used a lot inpackaging. Polyvinyl chloride (PVC) consists of vinyl chloride monomers. PVC is used to make pipesand flooring. Polyethene, or polyethylene, is made from ethene monomers. Polyethene is used to makefilm wrapping, plastic bags, electrical insulation and bottles. Polytetrafluoroethylene is used in non-stick frying pans and electrical insulation. Everything Science
  6. 6. 6Plastics continuedA thermoplastic can be heated and melted to a liquid. It freezes to a brittle, glassy statewhen cooled very quickly. Examples of thermoplastics are polyethene and PVC.A thermoset plastic cannot be melted or re-shaped once formed. Examples of thermosetplastics are vulcanised rubber and melanine.It is not easy to recycle all plastics, and so they create environmental problems.Some of these environmental problems include issues of waste disposal, air pollution andrecycling. Image by Doug Lee Everything Science
  7. 7. 7Biological macromoleculesA biological macromolecule is a polymer that occurs naturally in living organisms.Examples of biological macromolecules include carbohydrates and proteins, both of which areessential for life to survive.Carbohydrates include the sugars and their polymers, and are an important source of energyin living organisms.Glucose is a carbohydrate monomer. Glucose is the molecule that is needed for cellularrespiration. The glucose monomer is also a building block for carbohydrate polymers such asstarch, glycogen and cellulose. Everything Science
  8. 8. 8ProteinsProteins have a number of important functions. These include their roles in structures,transport, storage, hormonal proteins and enzymes.A protein consists of monomers called amino acids, which are joined by peptide bonds.A protein has a primary, secondary and tertiary structure. Everything Science
  9. 9. 9Amino acids and DNAAn amino acid is an organic molecule,made up of a carboxyl and an aminogroup, as well as a carbon side chain ofvarying lengths.It is the sequence of amino acids thatdetermines the nature of the protein.It is the DNA of an organism thatdetermines the order in which aminoacids combine to make a protein.DNA is a nucleic acid. DNA is a polymer,and is made up of monomers callednucleotides.Each nucleotide consists of a sugar, aphosphate and a nitrogenous base. It isthe sequence of the nitrogenous basesthat provides the ’code’ for thearrangement of the amino acids in aprotein. Everything Science
  10. 10. 10For more practice or to ask an expert for help on thissection Everything Science