Molecules of life

, , – or – are major nutrients that we need in large quantities – in grams rather than milligrams or micrograms.

We get these by eating them. They are broken down first and then reassembled into our own carbohydrates, proteins and lipids. This is because:

most of the molecules in food are too large to pass through the absorbing surface of the gut wall
the carbohydrates, proteins and lipids are reassembled in the form required, rather than other animal or plant versions

Nutrient	Major function	Major sources
Carbohydrates	Source of energy, glucose is the main respiratory substrate	Starch: Potatoes, rice and wheat products – bread, cereals and pasta. Sugars: fruit, smoothies, fizzy drinks, chocolate and sweets.
Proteins	Growth and repair	Meat, eggs, cheese, beans, nuts and seeds
Lipids	Energy, make up part of cell membranes, so essential for normal growth	Butter and margarine, meat and processed meat, plant oils, oily fish, nuts and seeds

Nutrient	Carbohydrates
Major function	Source of energy, glucose is the main respiratory substrate
Major sources	Starch: Potatoes, rice and wheat products – bread, cereals and pasta. Sugars: fruit, smoothies, fizzy drinks, chocolate and sweets.

Nutrient	Proteins
Major function	Growth and repair
Major sources	Meat, eggs, cheese, beans, nuts and seeds

Nutrient	Lipids
Major function	Energy, make up part of cell membranes, so essential for normal growth
Major sources	Butter and margarine, meat and processed meat, plant oils, oily fish, nuts and seeds

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