4.3 Naturally Occuring Polymers

Question 1

DNA - polymers (4)

Answer 1

• DNA is a complex molecule that contains genetic information.
• It contains two strands made of monomers called nucleotides that bond together in a polymerisation reaction.
• There are four different nucleotide monomers in DNA, referred to by letters - A, G, C and T.
• Short sequences of these nucleotide monomers in DNA are called genes. These allow organisms to function and develop.

Question 2

Carbohydrates - polymers (2)

Answer 2

• Carbohydrates are molecules containing carbon, oxygen and hydrogen, used by living things to store energy.
• Starch, cellulose and glycogen are large, complex carbohydrates, which are made up of many smaller units of carbohydrates, known as sugars or fructose, joined together in a long chain.

Question 3

Which three functional groups do amino acids contain?

Answer 3

A carboxyl group (carboxylic acid group) an amino group and an ‘R’ group.

Question 4

Amino acids (3)

Answer 4

• Amino acids contain an amino group, a carboxyl group (a carboxylic acid group) and an ‘R’ group.
• Amino acids form polymers known as proteins via condensation polymerisation.
• Proteins have many important uses in the human body, e.g. as enzymes

Question 5

Which monomers combine to form a polypeptide?

Answer 5

Amino acids

Question 6

What do polypeptides from once they fold up?

Answer 6

A protein

Question 7

DNA molecules consist of ___ polymer chains that coil around each other in a double _____. This helps to protect the DNA from _______.

Answer 7

two, helix, damage

Question 8

What are the three elements that makes up carbohydrates

Answer 8

Oxygen, Carbon, Hydrogen

Question 9

What are three examples of carbohydrate polymers?

Answer 9

Glycogen, Starch and Cellulose

Question 10

What are 2 examples of carbohydrate monomers?

Answer 10

Glucose & Fructose

Question 11

Describe how the atoms in a chains of monomers are held together in polymers (5)

Answer 11

• In polymers, all the atoms in a chain are joined by strong covalent bonds.
• There are intermolecular forces between the chains.
• The intermolecular forces between polymer molecules are stronger than between simple molecules, so more energy is needed to break them. This means most polymers are solid at room temperature.
• The intermolecular forces are still weaker than ionic or covalent bonds, so polymers generally have lower melting points than ionic or giant covalent compounds.
• Before polymers melt, they become soft. The weaker the forces between the chains, the lower the softening point of a polymer.

Question 12

Describe how density can influence the properties of a polymer (2)

Answer 12

• Low density (LD) poly(ethene) is made from ethene. There’s lots of space between the polymer chains, so the forces between the chains are relatively weak. This means it’s flexible and so is used for bags and bottles.
• High density (HD) poly(ethene) is also made from ethene but under different conditions. The chains are packed more closely together, so the forces between them are stronger. So it’s stiff and is used for water tanks and drainpipes.

Question 13

Polymers that only have intermolecular forces between the chains

Answer 13

Polymers that only have intermolecular forces between the chains are made up of individual tangled chains that can slide over each other. The forces between the chains can be overcome, so the polymers can be melted.

Question 14

Polymers that have crosslinks between the chains

Answer 14

In polymers that have crosslinks between the chains as well as intermolecular forces, the chains are held together very strongly. These polymers don’t soften when they’re heated. The chains are held together in a rigid structure, making them strong, hard and stiff.