CELL BIOLOGY
Cell Biology - Respiration and Photosynthesis
Breathing Yeast
- Materials you need are:
- a sachet of bakers' yeast (from the supermarket)
- plastic bags
- a teaspoon
- sugar
- 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.
Cell Biology - Cell Types
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:
A CITY |
A CELL |
| 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 Yogurt
- Safety rules:
- Parent supervision
- Take care with heat or fire
- Do not eat this if you are lactose-intolerant
- Materials you need are:
- natural yogurt
- full cream milk
- one litre container with a lid
- a saucepan
- a tablespoon
- a measuring cup
- a stove
- a thermometer
Place about 500 mL 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 45oC (luke-warm), add 1 tablespoon or 20 grams of natural yogurt to the milk. Allow this to set for about 6 hours. Then refrigerate and eat.
Yogurt contains bacteria that will reproduce rapidly in the milk to make even more yogurt within a short period of time. The bacteria in yogurt are very good for you and the milk proteins and sugars are highly nutritious.