Building Large Molecules from Small Ones Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

How glucose is converted to starch, glycogen and cellulose, and how lipids and proteins are synthesised from smaller molecules.

• Explain how glucose is used to make starch, glycogen and cellulose
• Describe how plants use glucose to make lipids
• Apply knowledge of how plants use glucose and nitrate ions to make amino acids
• Compare the structure and function of different biological macromolecules

Key ideas to keep in view

Use this lesson to stay inside B1.3 Respiration while connecting the detail back to the wider B1: Cell level systems topic.

• B1: Cell level systems
• B1.3 Respiration
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from Building Large Molecules from Small Ones before testing yourself from memory.

• Your body is like a construction site that never stops building. Every second, cells are taking tiny molecules and sticking them together to make massive structures. Think of it like LEGO - you start with simple bricks and end up with complex models.
• But why bother? Why not use big molecules from the start? The answer is efficiency and control. Small molecules are easier to transport, store, and modify. When you need a specific structure, you build it to order.
• A reaction that joins small molecules together to make larger molecules.
• Small molecules join together to make larger molecules.
• Cells join small molecules together to make larger molecules such as starch, proteins and fats.
• Glucose is the Swiss Army knife of biology. This simple sugar can be transformed into three completely different polymers, each with a unique job. It's like having one type of brick that can build a wall, a bridge, or a tower depending on how you arrange it.
• A storage polymer made from glucose monomers joined together. Found in plant cells as an energy reserve.
• A storage polymer made from glucose monomers with extensive branching. Found in animal cells, particularly liver and muscle, for rapid energy release.
• A structural polymer made from glucose monomers arranged in straight chains. Forms the cell walls of plants, providing strength and support.
• Trap: Many students think these are completely different molecules. Actually, they're all made from identical glucose units - the difference is in how the glucose molecules are connected and arranged.

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.