The effect of plant chemicals on humans
World Wide Fund for Nature (WWF-UK)
Weyside
Park,
Godalming, Surrey GU7 1XR
ENGLAND
The activity below is taken from:
“Science for
Survival: Plants and Rainforests in the Classroom” by Adam Cade, published
in 1988 by the Richmond Publishing Co. Ltd. Copyright Adam Cade, Richmond
Publishing Co. Ltd. WWF-UK.
This publication forms part of the WWF-UK Environmental
Education Project. The activity may be reproduced for non-profit, educational
purposes provided the source is acknowledged.
Scientists are continually discovering new properties of
chemicals found in plants. This is true even for well-known chemicals such as
caffeine. We know that caffeine, found in coffee beans, increases the pulse rate
and acts as a stimulant, but recent research suggests that coffee may increase
our blood cholesterol level, too. Other research has shown that caffeine may
have an effect against certain viruses such as herpes.
In the investigation below, you will find out how caffeine
affects your pulse rate:
You will need
1 cup of ordinary black coffee
1 cup of
decaffeinated black coffee
1 cup of warm water
Stopwatch
What to do
1. Three volunteer pupils (or multiples of three)
should record their pulse rates over 1 minute.
Figure
2. Each volunteer must then drink one of the three drinks.
3. They must record their pulse rate again over 1 minute at
intervals of 5. 10 and 15 minutes.
4. Copy and complete the following table.
