Get access to the common mistakes students make in their A-Level physics exams. Inspired by The Examiner's reports this is an un-missable opportunity to find out where precious marks are dropped.
We eat all sorts of food. It all looks very different, but if we examine it closely we can spot different food types.
There are three main food types: carbohydrates, proteins and fats...
Carbohydrates: Used to give us energy and come from sugary or starchy foods.
Fats: Also used to give energy but have other uses too.
Proteins: Important for building up muscle and other cells.
However, there are another four types of chemicals that are sometimes described as being 'food types'. These include minerals, vitamins, roughage and water.
Minerals: Simple ions (charged atoms) such as calcium, iron and fluoride.
Vitamins: More complex organic molecules.
Both Minerals and Vitamins are needed in only tiny amounts but have critical uses in the body and their absence causes disease.
Roughage: The indigestible bits of food that our body cannot cope with and so pass through unaffected.
Water: Also get this through drinks and in our food.
We have summarised these points for you below:
You can imagine that if we don't get some of all the foods that we need our bodies can become deficient in some of the important chemicals and we get ill.
See if you know which deficiencies cause which diseases, just click on the answer you think is correct and then mark your answer:
Without enough protein we cannot grow properly or be able to repair our cells. This problem is also seen in areas of the world suffering from famine - people can develop swollen abdomens from a disease called kwashiorkor.
Vitamin deficiencies are perhaps the best known examples of these diseases:
Scurvy is a disease once common amongst sailors and has the nasty symptoms of bleeding gums and lost teeth. The British navy found that eating limes stopped the disease. Much later it was found that this was due to the high amounts of vitamin C in citrus fruit. (That was why the American's started calling the British 'limeys').
A lack of vitamin D leads to your bones not hardening properly. This causes the disease rickets in which the leg bones are bent giving a 'bandy-legged' appearance.
Lack of minerals also causes problems, such as anaemia due to iron deficiency. Another example is poor tooth and bone development due to calcium deficiency.
The three main types of food have specific chemical tests that enable us to take any piece of food and test to see if it contains protein, fat or carbohydrate.
We can test for protein using the Biuret test. This involves adding the piece of food to a copper sulphate solution with a little sodium hydroxide added. The light blue colour changes to purple if proteins are present.
Food contains fat if a white emulsion (tiny droplets of fat in water) is made after mixing the food with water and ethanol. This is called the alcohol emulsion test.
Carbohydrates come either as starch or sugars.
If you add a few drops of iodine to food it will go blue/black if starch is present.
Have a look at this animation to see how this test is performed:
For sugars we can use Benedict's test. Here we boil up some of the food with Benedict's solution, the blue colour will change to an orange if sugars are present.