GCSE · Chemistry · Edexcel · Spec 1CH0

Biological polymers (DNA, starch, proteins)

What's a polymer? If you pictured a carrier bag, you're only half right. Some of the most important polymers are inside you right now.

Chemistry · Natural polymers

Three natural polymers, three monomers

Which natural polymer does each clue belong to?

Still to sort

DNA (0)

A polymer made of nucleotides.

Where the line is: Its monomers are nucleotides, not amino acids or glucose.

Starch (0)

A carbohydrate polymer made of glucose.

Where the line is: Its monomer is glucose, not nucleotides or amino acids.

Protein (0)

A polymer made of amino acids.

Where the line is: Its monomers are amino acids, and the links between them are peptide bonds.

11 of 11 still to sort.

Every clue below belongs to DNA, to starch or to proteins. Tap a clue, then tap the polymer it fits.

Watch out: Each polymer has its own monomer. Nucleotides, glucose and amino acids are not interchangeable.

Inside DNA

A schematic of DNA

View: Held together. Showing 2 layers: The two chains, Bonding between the bases

View

Layers

Explore

Switch the view, then tap each part to see what it does.

Bonding between the bases holds the chains together.

A simplified picture, not to scale.

How proteins are built

R stands for the rest of an amino acid molecule. It is different in different amino acids.

Tap a molecule to see what it does in the reaction.

Check your thinking

Which idea sounds most like you?

Jay is revising polymers and writes three notes. Only one of them is right.

Which note is closest to what you think right now?

Polymers are plastics made in factories, like poly(ethene). DNA and starch can't be polymers.DNA is one single long chain of nucleotides.DNA, starch and proteins are all built from the same monomer.DNA, starch and proteins are natural polymers. Each has its own monomer, and DNA is usually two chains.

How sure are you?

I'm sureI think soI'm guessing

Polymers are plastics made in factories, like poly(ethene). DNA and starch can't be polymers.

This is a common misconception

Easy mistake: poly(ethene) is a polymer, but not every polymer is a plastic. DNA, starch and proteins are natural polymers, each built from small monomer molecules that join together. They matter because natural polymers are important for life.

DNA is one single long chain of nucleotides.

This is a common misconception

The chain part is right, the 'one' is not. DNA is a polymer of nucleotides, but it is usually two long chains wrapped around each other in a double helix.

DNA, starch and proteins are all built from the same monomer.

This is a common misconception

Each one has its own monomer: nucleotides for DNA, glucose for starch and amino acids for proteins. That is the whole point of asking 'what is the monomer?' about each polymer.

DNA, starch and proteins are natural polymers. Each has its own monomer, and DNA is usually two chains.

This matches the evidence

That's the whole picture: three natural polymers, three different monomers, and DNA usually in two chains.

Polymers aren't just plastics. DNA, starch and proteins are natural polymers, each with its own monomer.

Write it out

Explain it in your own words

Explain why the formation of a protein from amino acids is described as a condensation reaction. [3 marks]

Your answer

0 words · your answer stays on this page and is not sent anywhere.

The mark scheme

Amino acids join together (polymerise) to form a polypeptide / protein (1 mark)
Water is also produced when the amino acids join (1 mark)
A polymerisation that also produces water is a condensation reaction (1 mark)

Model answer

Amino acids join together to form polypeptides, which are the chains in a protein. Every time two amino acids join, a molecule of water is also produced. A polymerisation that makes water as well as the polymer is a condensation reaction.

Say what joins, say that water is also produced, then name the reaction type.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Polymers aren't just plastics. Life runs on them too.

What you need to know

A polymer is a long chain built from small monomer molecules joined together.
DNA, starch and proteins are natural polymers, and natural polymers are important for life.
Have a goSam says: 'Polymers are only plastic bags and bottles.' Name one thing from this page that proves Sam wrong.
DNA, starch or proteins: any one of them.
All three are natural polymers, each built from small monomer molecules joined together, so polymers are not only plastics.
DNA's monomers are nucleotides, and each nucleotide is made of a phosphate, a sugar and a nitrogenous base.
Four different bases, adenine (A), thymine (T), guanine (G) and cytosine (C), give four different nucleotides.
Have a goEvery nucleotide has the same kinds of parts. Which part is the one that differs between the four nucleotides?
The nitrogenous base.
There are four different nucleotides because there are four different bases (A, T, G and C).
DNA carries the genetic code, and it is usually two long chains wrapped around each other in a double helix.
Sugar–phosphate bonding forms the backbone of each chain; bonding between the bases holds the two chains together.
Have a goPicture DNA as a twisted ladder whose two sides are the backbones. What makes up the rungs?
Bonding between the bases.
The backbone runs along each chain, but it is the bonding between the bases that holds the two chains together.
Starch is a carbohydrate (carbon, hydrogen and oxygen atoms) made from glucose monomers, C₆H₁₂O₆.
Proteins are polymers of amino acids, and a protein contains one or more polypeptide chains.
Every amino acid has a carboxylic acid group (COOH) and an amine group (NH₂), and joining them makes peptide bonds.
Have a goWhich of the two groups on an amino acid contains nitrogen, COOH or NH₂?
NH₂, the amine group.
COOH is the carboxylic acid group (carbon and oxygen); the amine group, NH₂, is the one with nitrogen.
Water is also produced when amino acids join, so making a polypeptide is a condensation reaction.

The big picture

DNA, starch and proteins are natural polymers, each built from its own monomer: nucleotides, glucose and amino acids. DNA is usually two chains in a double helix, and joining amino acids to make proteins gives off water, so it is a condensation reaction.

Key points

1DNA, starch and proteins are natural polymers: each is a long chain built from small monomers.

2The monomers are different: nucleotides for DNA, glucose (C₆H₁₂O₆) for starch and amino acids for proteins.

3DNA is usually two chains in a double helix, with bonding between the bases holding the chains together.

4Amino acids have a COOH and an NH₂ group and join by peptide bonds to make polypeptides.

5Water is produced when amino acids join, so forming a protein is a condensation reaction.

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Worked example

Problem

One polypeptide chain is made by joining 6 amino acids in a single chain. How many peptide bonds form, and how many molecules of water are produced?

⚠ Watch out

Thinking 'polymer' means 'plastic', or that DNA is one chain. DNA, starch and proteins are natural polymers, and DNA is usually two chains. Also, don't mix up the monomers: nucleotides, glucose and amino acids each belong to one polymer.

🧠

Memory hook

Same question, three answers. What's the monomer? DNA: nucleotides. Starch: glucose. Protein: amino acids. And for proteins, every join lets a molecule of water escape.

✓

Check yourself

Cover the page. Write down the three natural polymers and the monomer each one is built from. Then add one fact about each polymer that the other two don't share.

Flashcards

(14)

What do we call DNA, starch and proteins?

Natural polymers: each is built from small monomer molecules joined together, and natural polymers are important for life.

What is the monomer of DNA?

A nucleotide.

What is the monomer of starch?

Glucose, molecular formula C₆H₁₂O₆.

What is the monomer of a protein?

An amino acid.

What three parts make up one nucleotide?

A phosphate, a sugar and a nitrogenous base.

Which four bases are found in DNA?

Adenine (A), thymine (T), guanine (G) and cytosine (C).

Why does DNA have four different nucleotides?

Because there are four different bases.

What does DNA's shape look like?

Usually two long polymer chains wrapped around each other: a double helix.

What holds the two chains of DNA together?

Bonding between the bases.

What does DNA do for living organisms and viruses?

It carries the genetic code they need to develop and carry out life processes.

What type of compound is starch, and which atoms does that type contain?

A carbohydrate: carbon, hydrogen and oxygen atoms.

Which two functional groups does every amino acid contain?

A carboxylic acid group (COOH) and an amine group (NH₂).

What links amino acids together in a polypeptide?

Peptide bonds.

What else is produced when amino acids polymerise, and what does that make the reaction?

Water, so it is a condensation reaction.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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Three natural polymers, three monomers

Which idea sounds most like you?

Explain it in your own words

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