Edexcel iGCSE Biology-2.7 identify chemical elements- Study Notes- New Syllabus
Edexcel iGCSE Biology-2.7 identify chemical elements- Study Notes- New syllabus
Edexcel iGCSE Biology-2.7 identify chemical elements- Study Notes -Edexcel iGCSE Biology – per latest Syllabus.
Key Concepts:
2.7 identify the chemical elements present in carbohydrates, proteins and lipids (fats and oils)
Chemical Elements in Carbohydrates, Proteins & Lipids
📝 Introduction
- All living organisms are made up of the same basic chemical elements.
- The main biological molecules are carbohydrates, proteins, and lipids (fats & oils).
- Each has a unique combination of elements → linked to their function.
🍞 Carbohydrates 
- Made of Carbon (C), Hydrogen (H), and Oxygen (O).
- Ratio: usually 1 Carbon : 2 Hydrogen : 1 Oxygen (like glucose, C₆H₁₂O₆).
- Function: Main source of energy (respiration).
- Mnemonic: CHO = “See HOw sweet sugars are!”
🍗 Proteins
- Made of Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).
- Many proteins also contain Sulfur (S) (in amino acids like cysteine, methionine).
- Function: Growth, repair, enzymes, hormones, antibodies.
- Mnemonic: CHON(S) = “Proteins are CHaNceS for life.”
🥑 Lipids (Fats & Oils)
- Made of Carbon (C), Hydrogen (H), and Oxygen (O).
- Proportion: much less Oxygen than in carbohydrates.
- Function: Long-term energy storage, insulation, cell membranes.
- Mnemonic: CHO (low O) = “Lipids are CHO but low on O.”
📊 Summary Table – Elements in Biological Molecules
| Molecule | Elements Present | Notes |
|---|---|---|
| Carbohydrates | C, H, O | Ratio ~ 1:2:1, energy source |
| Proteins | C, H, O, N (+S) | Amino acids → growth, enzymes, hormones |
| Lipids | C, H, O (low O) | Energy storage, membranes, insulation |
⚡ Quick Recap
Carbohydrates = CHO (sweet sugars).
Proteins = CHON(S) (nitrogen makes them different).
Lipids = CHO (but less oxygen).