Nutrients: sources and functionsSpec 2.25
In short
Each nutrient has a source and a specific function. Carbohydrate provides energy, protein is needed for growth and repair, and lipid is an energy store and insulation. Vitamin A is needed for vision in dim light, vitamin C keeps skin and gums healthy, vitamin D helps absorb calcium, calcium builds bones and teeth, and iron is needed to make haemoglobin.
You need to know a source and a function for each of the nutrients in the table.
| Nutrient | Sources | Functions |
|---|---|---|
| Carbohydrate | Bread, pasta, rice, potatoes | Provides energy (released by respiration) |
| Protein | Meat, fish, eggs, beans | Growth and repair of tissues. Proteins are made from amino acids. |
| Lipid (fats and oils) | Butter, cooking oils, nuts, oily fish | Energy store, insulation (keeps heat in), and part of cell membranes |
| Vitamin A | Liver, carrots, dairy foods | Healthy eyes and vision in dim light. A lack causes night blindness. |
| Vitamin C | Citrus fruits, fresh vegetables | Keeps skin and gums healthy. A lack causes scurvy. |
| Vitamin D | Oily fish, eggs, margarine (also made in skin in sunlight) | Helps the body absorb calcium. A lack causes weak bones (rickets in children). |
| Calcium (mineral ion) | Milk, cheese, green vegetables | Needed for strong bones and teeth |
| Iron (mineral ion) | Red meat, liver, spinach | Needed to make haemoglobin in red blood cells. A lack causes anaemia. |
| Water | Drinks and most foods | Solvent for chemical reactions, and the main part of blood plasma, which transports substances |
| Dietary fibre | Wholemeal bread, vegetables, fruit | Adds bulk, which helps peristalsis move food through the gut and prevents constipation |
Exam tip:
Mark schemes want a specific function, not just 'it is good for you'. Learn one clear function for each nutrient. Fibre is not digested, so it provides no energy.
Written and checked against the Edexcel IGCSE Biology (4BI1) specification · Updated October 2026