Carbohydrates: sugars, starch and fibre
Carbohydrates, fats and proteins are organic compounds made by living things. Carbohydrates contain only carbon, hydrogen and oxygen. We find them in bread, rice, potatoes, grains, fruit and vegetables. We sort them by size. Single sugars have one unit: glucose and fructose. Double sugars have two units: sucrose (glucose + fructose) and maltose (glucose + glucose). Small chains have 3 to 9 units, like raffinose in beans. Long chains have more than 9 units: starch and cellulose. Glucose is the sugar our cells use for energy, and the brain relies on it. Plants store their food as starch, and use cellulose in their cell walls; paper is mostly cellulose. Extra carbohydrate in our bodies is stored as glycogen in the liver and muscles, or as fat. Be careful: the idea that all carbohydrates taste sweet is wrong. Starch and cellulose are not sweet.
| Size | Units | Examples |
|---|---|---|
| single sugar | 1 | glucose, fructose |
| double sugar | 2 | sucrose, maltose |
| small chain | 3–9 | raffinose (in beans) |
| long chain | more than 9 | starch, cellulose |
Kitchen sort, with a grown-up. Choose eight foods (for example bread, rice, apple, potato, beans, honey, oats, lettuce). Sort them by main nutrient. Stir a spoon of sugar and a spoon of cornflour in two glasses of cold water and describe what you see in each glass. Do not use iodine or any test chemicals, and do not taste a test mixture.