AQA GCSE Chemistry Foundation (8462), Foundation tier · Organic chemistry › Synthetic and naturally occurring polymers
Practise DNA and other naturally occurring polymers. 7 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
DNA and the other natural polymers that are important for life (proteins, starch and cellulose), and the monomers they are made from. GCSE Chemistry only. Expect short recall questions, often 1 mark each, and 'describe the structure of DNA'.
Key facts
DNA = deoxyribonucleic acid, a large molecule essential for life
DNA encodes genetic instructions for the development and functioning of living organisms and viruses
DNA: two polymer chains, four different nucleotides, double helix
DNA is made from nucleotides
Proteins are made from amino acids
Starch is made from sugars (glucose)
Cellulose is made from sugars (glucose)
Notes
DNA
diagram
DNA (deoxyribonucleic acid) is a large molecule that is essential for life.
DNA encodes the genetic instructions for the development and functioning of living organisms and viruses.
Most DNA molecules are two polymer chains in the form of a double helix.
DNA: two chains of nucleotides twisted into a double helix. The order of the nucleotides is the genetic code.
The chains are made from four different monomers called nucleotides.
The order (sequence) of the nucleotides along the chains carries the genetic instructions. DNA molecules are very long, so they can hold a huge amount of information.
Other natural polymers
Proteins: the monomers are amino acids.
Starch: the monomers are sugars (glucose).
Cellulose: the monomers are also sugars (glucose). Starch and cellulose are both made by plants.
Like synthetic polymers such as poly(ethene), natural polymers are very long molecules made from many monomers joined together.
How to answer each type of question
Match polymers to their monomers
1 mark eachGrade 4
Learn the four pairs: DNA and nucleotides, proteins and amino acids, starch and sugars, cellulose and sugars.
Glucose is the sugar in starch and cellulose, so you can give either word.
Draw one straight line from each box, and do not join one box to two others.
Example. Draw one line from each polymer to the monomer it is made from. Polymers: cellulose, DNA, protein Monomers: amino acids, ethene, glucose, nucleotides
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Cellulose to glucose (1) DNA to nucleotides (1) Protein to amino acids (1)
Describe the structure of DNA
2 to 3 marksGrade 5
Say that it is made of two polymer chains.
Say that the monomers are four different nucleotides.
Say that the chains form a double helix.
Example. A student writes: 'DNA is a single polymer chain made from one type of monomer.' Give two ways in which the student's description is wrong, and name the shape of a DNA molecule.
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DNA is (usually) two polymer chains, not one (1). It is made from four different monomers (nucleotides), not one type (1). The shape is a double helix (1).
Don’t lose marks
Saying DNA is made from amino acids. DNA is made from nucleotides; proteins are made from amino acids.
Writing 'double helix' but not saying that there are two polymer chains made from four different nucleotides.
Saying starch and cellulose are made from different monomers. Both are made from glucose (a sugar).
Saying DNA only carries instructions for humans or animals. It does so for all living organisms and for viruses.
More tips
Memory tricks
Two S's: Starch and cellulose are both made of Sugar (glucose).
P and A: Proteins are made of Amino acids.
DNA in numbers: 2 chains, 4 different nucleotides, 1 double helix.
Natural polymers are nature's plastics: long chains of repeating monomers.
Exam technique
Most questions here are 1-mark recall: learn the exact key words, such as 'nucleotides', 'double helix' and 'genetic instructions'.
'Describe the structure of DNA' is usually 3 marks: two polymer chains, four different nucleotides, double helix.
In matching questions, one line from each box. Two lines from the same box lose the mark.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Name natural polymers that are important for lifeDNA, proteins, starch and cellulose.
Grade 4
Name the monomers of each natural polymerDNA: nucleotides. Proteins: amino acids. Starch and cellulose: sugars (glucose).
Grade 4
State what DNA doesDNA encodes the genetic instructions for the development and functioning of living organisms and viruses.
Grade 5
Describe the structure of DNATwo polymer chains, made from four different nucleotides, in the form of a double helix.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Give the name of the shape of a DNA molecule.
Double helix
Starch and cellulose are also naturally occurring polymers. Name the monomer used to make both starch and cellulose.
Glucose (a sugar)
Name the monomers that join together to make proteins.
Amino acids
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
(a) What are the monomers of starch? Tick (✓) one box.[1]
Sugars (glucose)
Amino acids
Nucleotides
Alkenes
(b) What are the monomers of proteins? Tick (✓) one box.[1]
Sugars
Amino acids
Nucleotides
Esters
(c) What are the monomers of DNA? Tick (✓) one box.[1]
Sugars
Amino acids
Nucleotides
Alkanes
(d) Give the name of the shape of a DNA molecule.[1]
Show the answer and mark scheme
(a)Answer: Sugars (glucose)
(b)Answer: Amino acids
(c)Answer: Nucleotides
(d)Answer: Double helix
double helix
Question 2Medium5 marks
DNA (deoxyribonucleic acid) is a large molecule that is essential for life.
(a) Describe the structure of a DNA molecule.[3]
(b) What is the function of DNA?[1]
(c) Starch and cellulose are also naturally occurring polymers. Name the monomer used to make both starch and cellulose.[1]
Show the answer and mark scheme
(a)Answer: Two polymer chains made from four different nucleotides, twisted into a double helix.
two polymer chains
made from four different monomers called nucleotides
in the form of a double helix
(b)Answer: It encodes the genetic instructions for the development and functioning of living organisms and viruses.
it encodes genetic instructions (for the development and functioning of living organisms and viruses)