Edexcel iGCSE Biology-2.8 structure of carbohydrates, proteins and lipids- Study Notes- New Syllabus
Edexcel iGCSE Biology-2.8 structure of carbohydrates, proteins and lipids- Study Notes- New syllabus
Edexcel iGCSE Biology-2.8 structure of carbohydrates, proteins and lipids- Study Notes -Edexcel iGCSE Biology – per latest Syllabus.
Key Concepts:
2.8 describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units: starch and glycogen from simple sugars, protein from amino acids, and lipid from fatty acids and glycerol
Structure of Carbohydrates, Proteins & Lipids
📝 Introduction
Biological molecules like carbohydrates, proteins, and lipids are called macromolecules (large molecules).
They are built by joining together smaller basic units (monomers) into polymers.
🍞 Carbohydrates
- Basic unit (monomer): simple sugars (monosaccharides) e.g., glucose.
- Large molecules (polymers):
– Starch (plants) → long chains of glucose.
– Glycogen (animals) → branched chains of glucose. - Function: Energy storage (starch in plants, glycogen in animals) and quick energy supply (glucose).
- Trick: “Sugars (small) → Starch/Glycogen (big storage).”
🍗 Proteins
- Basic unit (monomer): amino acids.
- ~20 different amino acids → joined in sequences to make different proteins.
- Large molecule (polymer): polypeptide chain (many amino acids linked by peptide bonds).
- Function: Growth, repair, enzymes, hormones, antibodies.
- Trick: “Amino acids are letters → proteins are words/sentences.”
🥑 Lipids (Fats & Oils)
- Basic units (monomers): glycerol + fatty acids.
- 1 lipid molecule = 1 glycerol + 3 fatty acids (called a triglyceride).
- Function: Long-term energy store, insulation, protection, cell membranes.
- Trick: “3 fatty acids hug 1 glycerol = fat molecule.”
📊 Summary Table – Structure of Macromolecules
| Molecule | Small Units (Monomers) | Large Molecule (Polymer) | Function |
|---|---|---|---|
| Carbohydrates | Simple sugars (glucose) | Starch (plants), Glycogen (animals) | Energy supply & storage |
| Proteins | Amino acids | Polypeptides / Proteins | Growth, repair, enzymes |
| Lipids | Glycerol + Fatty acids | Triglycerides | Energy storage, insulation, membranes |
⚡ Quick Recap
Carbs → Glucose (sugar) → Starch/Glycogen.
Proteins → Amino acids → Polypeptides/Proteins.
Lipids → 1 Glycerol + 3 Fatty acids → Triglyceride.