Biological Molecules: Biological Molecules
4.1 Biological Molecules
Chemical Elements In Molecules
- Carbohydrates → Carbon (C), Hydrogen (H), Oxygen (O)
- Lipids → C, H, O (less oxygen than carbohydrates)
- Proteins → C, H, O, Nitrogen (N), sometimes Sulfur (S)
- DNA → C, H, O, N, Phosphorus (P)
Large Molecules Made From Small Units
| Large Molecule | Built From | Examples |
|---|---|---|
| Starch, Cellulose, Glycogen | Glucose units | Plant starch, plant cell walls, animal storage |
| Proteins | Amino acids | Enzymes, hormones, structural proteins |
| Lipids (fats/oils) | Fatty acids + Glycerol | Oils, butter |
| DNA | Nucleotides | Genetic material |
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course
Food Tests
| Test | Reagent | Positive Result |
|---|---|---|
| Starch | Iodine solution | Blue-black |
| Glucose (reducing sugar) | Benedict’s solution + heat | Brick-red |
| Protein | Biuret test (sodium hydroxide + copper sulfate) | Purple |
| Lipids | Ethanol emulsion test | White emulsion |
Key Notes
- Glucose = main respiratory substrate.
- Glycogen = storage carbohydrate in animals.
- Cellulose = structural carbohydrate in plant cell walls.
- Proteins = enzymes, antibodies, hormones.
- Lipids = insulation, energy store, membranes.
- DNA = carries genetic information.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course