Science Revision Cards

Carbohydrate To provide energy Cereals, bread, pasta and potatoes

Protein For growth and repair Fish, meat, eggs and dairy products

Fat To provide energy. Also to store energy in the body and insulate it against the cold Butter, oil and nuts

Minerals Needed in small amounts to maintain health Salt, milk (for calcium) and liver (for iron)

Vitamins Needed in small amounts to maintain health Dairy foods, fruit, vegetables

Fibre To provide roughage to help to keep the food moving through the gut Vegetables, bran

Water Needed for cells and body fluids Fruit juice, milk, water

Microbes

Many living things are so small that they can only be seen through a microscope. These living things are called micro-organisms or microbes. There are three main types of microbe:

• fungi
• bacteria
• viruses

Fungi

Mushrooms and toadstools are fungi, but these are made of lots of cells, so they are not microbes. Yeasts are single-celled fungi, so they are microbes. Fungi are usually the biggest type of microbe. If there is just one of them, we call it a fungus.

Bacteria

Bacteria are usually smaller than fungi. If there is just one of them, we call it abacterium. Bacteria have many different shapes. Some have 'tails' (called flagella) that let them swim.

Viruses

Viruses are the smallest type of microbe. As a virus can only reproduce inside a cell, some people are not convinced that viruses are really living things.

Microbes - useful or not?

People often use the word germ instead of microbe, so you might think that microbes are all harmful. But some are useful to us.

Useful microbes

Yeast cells are useful to bakers and brewers. Yeast cells can change sugar into carbon dioxide, gas and alcohol. This is useful to bakers because the gas helps the bread rise, and it is useful to brewers because it adds the alcohol needed for their drinks.

Bacteria are also useful to us. For example, certain bacteria cause the changes needed in milk to make yogurt and cheese out of it.

Harmful microbes

Here are some diseases caused by bacteria:

• tuberculosis, TB (affects the lungs)
• salmonella (causes food poisoning)
• whooping cough (affects the lungs)

Here are some diseases caused by viruses:

• chicken pox (affects skin and nerves)
• common cold
• influenza, flu
• measles (affects skin and lungs)
• mumps (affects salivary glands)
• rubella, german measles

Microbes cause disease when they are able to reproduce in the body. They produce harmful substances called toxins, and damage tissues and organs. We say that someone who has harmful disease-causing microbes in them is infected.