Experiments: Cells

Breathing Yeast

Materials you need are:
a sachet of bakers' yeast (from the supermarket)
plastic bags
a teaspoon
warm water

Put the same amount of yeast in each of 2 plastic bags. Add the same amount of warm water to each. Add different amount of sugar in each and seal. Put both bags in a warm place and leave for a day. What do you notice?

Yeast is a living fungus and respires as animals do. This means they use sugar and oxygen to make their energy, some water and some carbon dioxide. The more sugar they have, the more carbon dioxide gas they should make.

Design a Cell

Use only pen and paper to design a cell. Think of how a city works - government, power station, factories, warehouses, transport within the city and to other cities, sanitation and so on. Draw how you think a cell should work.

Your ideas will probably be similar to a real cell. It is surrounded by a membrane and has a certain limited size to support its activities without becoming inefficient. Some examples are below:

government nucleus
trees to make oxygen chloroplasts
power stations to make energy mitochondria
factories ribosomes that make proteins
warehouses and roads for storage, sorting and transport endoplasmic reticulum, golgi bodies and vacuoles
sanitation lysosomes

Make Yoghurt

Safety rules:
Parent supervision
Take care with heat or fire
Do not eat this if you are lactose-intolerant

Materials you need are:
natural yoghurt
full cream milk
one litre container with a lid
a saucepan
a tablespoon
a measuring cup
a stove
a thermometer

Place about 500 millilitres of milk into a saucepan and heat it until it starts to boil. Keep the milk at boiling point for about 3 minutes and then allow it to cool. When the milk has cooled to a temperature of 45 °C (lukewarm), add 1 tablespoon or 20 grams of natural yoghurt to the milk. Allow this to set for about 6 hours. Then refrigerate and eat.

Yoghurt contains bacteria that will reproduce rapidly in the milk to make even more yoghurt within a short period of time. The bacteria in yoghurt are very good for you and the milk proteins and sugars are highly nutritious.