Lesson focus: What do starchA substance plants use to store food, found in potatoes, rice and bread., proteinA nutrient used for growth and repair, found in foods like meat, eggs and beans. and DNAThe chemical in cells that carries the instructions for how a living thing grows and works. have in common?
Identify natural polymerA polymer made by living things, such as starch or wool. and relate their structures to biological roles.
Build on earlier learning
Plant and animal cellsReconnect cell walls and genetic material with the molecules that form them.
Practical
Building a DNA model
- Join sugar–phosphate pieces to make two backbones.
- Pair the bases: A with T and C with G.
- Twist the ladder to show the double helix.
Record: A labelled photo or drawing and the base sequence of the second strand.
You will be successful when you can…
- Name four natural polymers.
- Identify their building units.
- Match each to a biological role.
- Explain why similar units can form different materials.
Words that carry the science
- natural polymer
- A polymer produced by living organisms.
- starch
- A glucose polymer used for energy storage in plants.
- cellulose
- A glucose polymer forming strong plant cell walls.
- amino acid
- A small molecule used as a building unit of proteins.
- nucleotide
- A building unit of DNA containing a sugar, phosphate and base.
- enzyme
- A protein that speeds up a chemical reaction in living organisms.
Connect building units, arrangement and biological function
01Living organisms make polymers
Plants make starchA substance plants use to store food, found in potatoes, rice and bread. for energy storage and celluloseA tough substance that makes plant cell walls strong. for cell-wall support. Both use glucose building units, but those units are joined and arranged differently.
02Sequence matters
Proteins are chains of amino acidA small building block that joins with others to make proteins.. Their amino-acid sequence affects folding and function; some proteins are enzymeA protein that speeds up chemical reactions in living things, such as breaking down food.. DNA is built from nucleotideOne of the small building blocks that join together to make DNA. whose base sequence stores genetic information.
03Digestion makes absorbable units
Large food polymers are generally too large to cross the gut wall efficiently. Digestion breaks them into smaller soluble molecules that can be absorbed.
Explain different glucose-polymer functions
Starch and cellulose are both built from glucose. Why do they have different roles?
- Identify the shared building unit: glucose.
- State that the glucose units are linked or arranged differently.
- Different arrangement produces different three-dimensional structure and properties.
- Connect properties to energy storage in starch and structural support in cellulose.
How to make the reasoning visible: Building-unit identity alone does not determine polymer function.
Natural-polymer comparison
Match structure information to a defensible function.
| Polymer | Building unit | Main example role | Location/example |
|---|---|---|---|
| Starch | Glucose | Energy storage | Plant cells/seeds |
| Cellulose | Glucose | Structural support | Plant cell walls |
| Protein | Amino acids | Enzyme or structure | Cells and tissues |
| DNA | Nucleotides | Genetic information | Chromosomes/cells |
Why are proteins not all enzymes?
Why can starch digestion help absorption?
Use the table. Starch and cellulose are both made of glucose. Give one way they are different.
Check your understanding
Answer from memory, then check against the suggested answer.
What is a natural polymer?
What are proteins built from?
What are DNA chains built from?
Name one natural polymer found in plants.
What is the job of cellulose in plants?
A fibre contains cellulose. Why can it strengthen a plant cell wall but not serve as the plant’s main glucose store?
Why does a change in one DNA nucleotide sometimes alter a protein?
Why is starch broken down into glucose during digestion?
Exam Question Practice
Exam Question Practice
Mark points shown after marking
Name two natural polymers and state one correct function of each.
(4)Total for this question: 4 marks
Command word: Keep each polymer directly paired with its own function.