Animal organisation - digestion - AQAMolecules of life
The major nutrients required for a healthy diet are carbohydrates, proteins and lipids. The digestive system breaks down large molecules of food, which are then absorbed into the bloodstream.
carbohydrateFood belonging to the food group consisting of sugars, starch and cellulose. Carbohydrates are vital for energy in humans and are stored as fat if eaten in excess. In plants, carbohydrates are important for photosynthesis., proteinOrganic compound made up of amino acid molecules. One of the three main food groups, proteins are needed by the body for cell growth and repair., lipidFat or oils, composed of fatty acids and glycerol. (or fats) are major nutrients that we need in large quantities.
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
