Unit 2A 

Background Notes for Teachers

Over ten per cent of our body tissue is made of protein and we need to eat protein in order to renew it and , if you are growing, you need more protein to make more tissue.

Protein is made up of chemical units called amino acids. Protein in food is broken down in your body into individual amino acids. These are then rebuilt in your body into your cells to form the proteins you need. This is why your diet should include some of the following: lean meat, fish, cheese, eggs, milk, nuts and beans.

Carbohydrates are built up of different sugars and this is where we get most of our energy from. The sugars can be found directly in foods such as fruit or jam. However as starch becomes sugar inside your body it can also be found in foods such as potatoes, rice and bread.

If you eat more carbohydrates than you need the excess turns into glycogen which is either stored in your liver and muscles or is turned to fat. Too much sugar can lead to fat and is also bad for your teeth. This is why your diet should not include too many cakes, biscuits, sweets, chocolates and fizzy drinks.

Fats provide you with energy, just like carbohydrates. They also form the membranes of your cells. When fat is stored on the body, it helps keep us warm. Too much fat can give you heart disease. This is why although our diet should include foods such as fatty meat, milk, butter and cheese, vegetable oil and nuts, we should not eat too many of them.

We also need minerals such as calcium and phosphorous, found in milk and cheese, to help make and keep your bones and teeth strong; iron, found in liver and green vegetables is needed for your red blood cells; and zinc, found in nuts, fish and fresh vegetables. We also need a limited amount of sodium chloride, in the form of salt. This is why we must have a balanced diet.

Fibre and water are also important to keep our body working properly.

After we have eaten our food, it travels in soft lumps down our gullet and into our stomach. Once there the stomach mashes the food up into a soupy mixture and passes it along the small intestine where the nutrients are taken out.

The food stays in our stomach for about 3 hours, but it takes another 20 hours to pass right through our body!

We all make about 1.5 litres of saliva a day. Without it we wouldn't be able to eat our food, as we would be unable to chew or swallow.

Did you know that Popeye had it all wrong? In the 1890's nutrition experts put the decimal place in the wrong place when calculating its value and said that it contained ten times more iron than it really does. Spinach in fact gives you no more strength than any other greens!

We all need teeth to chew, there are 32 teeth in a full adult set, and 20 in the first set of teeth we have (often called milk teeth.)

Teeth are made of a strong outer layer of enamel, to enable us to bite, dentine in the body of the tooth (which is similar to bone), and a soft tissue called pulp which supplies the tooth with food and oxygen and is home to the nerves. The tooth is anchored into the jaw bone by the root and a thin layer of bone tissue.

Your heart pumps around your body day and night carrying oxygen from the lung to every part. Some of our blood vessels are so tiny we cannot see them, yet laid out end to end they would stretch around the world twice!

Your blood travels all around your body more than once every minute - but when you run fast your blood flows faster, up to five times as fast.

When we exercise a muscle can only contract - that's why they mostly work in pairs! Your biggest muscles are in your buttocks and thighs - the smallest are in your ears and are as thin as cotton thread.

It's an old saying, but it's true - it takes 10 muscles to smile but 12 to frown - why not save energy and smile!