|T H E N I H C A T A L Y S T||S E P T E M B E R O C T O B E R 2003|
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BUBBLING BILLIONS: A YEAST EXPERIMENT
For anything to grow, it needs the right conditions. In this experiment, were going to find out how to wake up something that looks like sanddry yeast.
Just looking at this stuff, youd never think it could be used to make bread, or wine, or pizza. But youll soon see that you can make this dull, dry sandpile just bubble over with enthusiasm!
First, it might be a good idea to get a grown-up to help you gather the ingredients and equipment youll need (and dont be surprised if the grown-up gets curious and wants to stick around to see what happens).
You will need:
A package of dry active yeast
Four small glasses (cordial size would be good, but test tubes would be even better)
A packet of sugar
Warm and cold tap water
Your sense of what is warm and cold is just fine. (You might also write down your observations, glance at the clock every now and then, and use some wooden chopsticks to stir.)
Now lets get started.
So that you remember what to do and what is in each glass container, label the four glasses (with a Post-It) with the following: 1) Yeast-warm-sugar. 2) Yeast-cold-sugar. 3) Yeast-warm. 4)Yeast-cold.
Step 1: Open the package of yeast and pour it on a plate. Theres not much there at alland were going to divide that little bit into quarters, too! (Not much? Well see.) Shake the dry yeast so it covers the plate, then divide it into quarters (an index card is a good tool for this). Put each quarter in its own glass.
Step 2: Into the two glasses that are marked to have sugar, sprinkle enough sugar to cover the surface of the yeasta healthy "pinch."
Step 3: Now for warm and cold. Fill a separate container with warm tap water that feels like bathwater and another separate container with cold tap water that feels like a cold soda. Then pour the warm water into the two yeast glasses that are marked for warm, and pour the cold water into the two yeast glasses that are marked for cold (look at the label to make sure, and pour the water almost to the top).
Step 4: Stir. Use separate stirrers for the glasses with and without sugar.
Step 5: Wait and wonderbut you wont have to wait long at all to see something happening.
So, what is it that makes dry, dull yeast wake up and bubble over? When you decide what that is, see if you can get all four yeast samples to behave like that.
Jennifer White, NIGMS
For more information about yeast (and action videos), see this website.
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