fully discuss and describe the processes of forming and breaking down polymers.

Formation: If we consider the formation of large molecules called polymers the process by which monomers are reacted together to form polymer chains or three dimensional networks is called polymerisation.
There are two types of polymerisation processes on the basis of the nature of monomer units.
(a) Homopolymerization
(b)Copolymerisation.
(a) Homopolymerization- If we talk about homopolymerization it is the process in which polymers are made up from the same type of monomers.
A+A+A+..........................→AAAA..........A+A+A+..........................→AAAA..........
For example: if we consider PVC it is a homopolymer and polyethene is also a homopolymer which is made up from ethane monomer units.
(b) Copolymerisation: Copolymerisation is a process in which polymers are made up from more than one monomer unit.
A+B+A+B.........→ABAB......A+B+A+B.........→ABAB......
For example: Styrene/butadiene copolymer (SBR) is an example of copolymer.
Both synthetic and natural polymers play an essential part in everyday life.
There are basically two types of polymerisation depending upon the mechanism.
(a) Step growth
(b) Chain growth
(a) Step growth polymerisation: In step growth polymerisation there is a removal of water or acid molecules from the combination of two monomers. Polymers formed are called condensation polymers.
(b) Chain growth polymerisation: In chain growth polymerisation the long chains are formed by the addition of monomers in larger numbers. This type of polymerisation involves the linking together of unsaturated monomers containing double bonds.
Polymers like polyethene . PVC is formed by the chain growth polymerisation. 

Breaking: First, the polymers are not easily broken down (degraded, depolymerized) into monomers. Depending on the chemical structures of polymers, specific conditions must be established to drive the polymer into the depolymerization process. Such extreme conditions (high temperatures/pressures) are not available inside our body. Second, only a few natural polymers (e.g., proteins, polysaccharides) can be broken down in our body through biochemical reactions in the presence of biocatalysts (enzymes). Human’s body cannot degrade artificial and some natural polymers (e.g., PE, cellulose) due to lack of the required conditions. When the products of depolymerization reactions have nutritional values for our body, they are used as source of energy and fuel. An example is sugars made from digestion of polysaccharides and aminoacides from proteins. If the monomers and products of polymers degradation have no nutritional values, they may be eliminated or act as toxic substances in our body.