Edexcel IGCSE Biology: A Balanced Diet

Carbohydrates

Needed to release energy in cells to enable life processes to take place.

Made of carbon, hydrogen, oxygen

good sources of carbohydrates

Rice, bread, potatoes, pasta, sugar

Lipids (fat and oils)

Provide energy, act as an energy store and provide insulation to maintain body temperature.

Built from fatty acids and glycerol

Contain carbon, hydrogen, oxygen

Good sources of fats/lipids

Fats: meat. Lipids: oils, milk products (e.g. butter, cheese), nuts, avocados, oily fish

Proteins

Broken down to make amino acids which are used to form enzymes and other proteins needed by cells. Needed for growth and repair of tissue, and to provide energy in emergencies.

Made up of amino acids

Contain carbon, nitrogen, oxyen, hydrogen

Good sources of protein

Eggs, milk, milk products (cheese, yoghurt etc), meat, fish, legumes (peas and beans), nuts and seeds.

Vitamin A

Helps to improve vision and keep your skin and hair healthy. Helps cells to grow.

Good food sources of vitamin A

Liver, red and orange vegetables (e.g. carrots), butter and fish oil.

Deficiency disease of vitamin A

night blindness

Vitamin C

prevent scurvy Important for making collagen (an important protein in blood vessels and skin), and for repairing bones and healthy teeth and gums. Keeps blood vessel linings healthy.

Good food sources of vitamin C

Citrus fruit, green vegetables, potatoes

Deficiency disease of Vitamin C

Scurvy (bleeding gums and wounds don't heal properly)

Vitamin D

Needed for calcium absorption. + strong bones and teeth

Good food sources of vitamin D

Fish, eggs, liver, cheese and milk

Deficiency disease of Vitamin D

Rickets (softening of the bones)

Calcium

Needed to make (strong) bones and teeth. Involved in clotting of blood.

good food sources of calcium

(Dairy products, e.g.) Milk and eggs

Deficiency disease of calcium

Rickets

Iron

Needed to make haemoglobin in red blood cells for healthy blood.

Good food source of iron

Red meats, liver and kidneys, leafy green vegetables e.g. spinach

Deficiency disease of iron

Anaemia (reduction in number of red blood cells, person soon becomes tired and short of breath)

Water

Just about every bodily function relies on water - we need a constant supply to replace water lost through urinating, breathing and sweating.

Dietary Fibre

Made up of plant cell walls. Aids the movement of food through digestive system (inclu. the gut) during peristalsis. Important in preventing constipation. Thought to help prevent bowel cancer.

What are the components of a balanced diet?

proteins, carbohydrates, lipids, vitamins and minerals, water, dietary fibre

vitamins and minerals

Needed in tiny amounts for correct functioning of the body. Cannot be produced by the body + some can be destroyed by cooking.