Biological Molecules Basics

IGCSE Edexcel Biology
2.7-2.8 Biological Molecules
Key Concept: Carbohydrates, proteins, and lipids are built from smaller units and contain specific elements.

Section A: Elements

1. State the elements found in carbohydrates, proteins, and lipids. [3]

Section B: Building Blocks

2. Explain how starch and glycogen are made from simple sugars. [2]
3. Describe how proteins are made from amino acids. [2]
4. Describe how lipids are made from fatty acids and glycerol. [2]

Section C: Functions

5. Identify the macromolecule for each function: long-term energy store, enzymes, cell membranes. [3]
Total marks: 12

Mark Scheme

1. Carbohydrates: C, H, O; Proteins: C, H, O, N (often S); Lipids: C, H, O [3]
2. Many glucose units join to form starch or glycogen (condensation to a polymer) [2]
3. Amino acids join to form polypeptides/proteins [2]
4. Glycerol bonds with fatty acids to form lipids [2]
5. Lipids, proteins, lipids (in order) [3]