1. Investigating Saliva
What you need to know:
How do we know that amylase digests starch to produce sugar?
How do we know that saliva contains amylase?
How do scientists solve complicated problems?
To Do:
List three facts about enzymes

2. Enzymes are specialised proteins that speed up chemical reactions in the body
Enzymes are used in digestion to break down large nutrients quickly
Most enzymes are destroyed by boiling
Today’s Problem: How can we be sure that
Amylase breaks down starch to produce sugars, and;
Saliva contains amylase?
Compare the contents of a starch solution before and after adding amylase
Compare the effect of amylase and saliva on starch solutions
Is this effect lost if we boil the saliva?

3. Today’s Problem: How can we be sure that
Amylase breaks down starch to produce sugars, and;
Saliva contains amylase?
Compare the contents of a starch solution before and after adding amylase
Compare the effect of amylase and saliva on starch solutions
Is this effect lost if we boil the saliva?
How can we get all this done in one lesson?
Work in teams and then share results!

4. To Do:
Read through your method
Identify any bits you do not understand
Carry out your experiment, following the instructions carefully
When you have completed your experiment:
- tidy away your equipment
- complete the tasks on the back of the sheet

5. Starch solution before heating with mixture
Experiment
Iodine Test
Benedict’s Test
Final
colour
Is starch present?
Is sugar present?
Starch solution before heating with mixture
After
with unboiled amylase
with boiled amylase
with unboiled water
with boiled water
with unboiled Saliva
with boiled Saliva
Black
Yes
Blue No
Orange No
Red
Yes
Black
Yes
Blue No
Black
Yes
Blue No
Black
Yes
Blue No
Orange No
Red
Yes
Black
Yes
Blue No

6. How do you know that the starch solution originally contained no sugar
How do you know that the starch solution originally contained no sugar? How do you know it contained starch?
We tested for sugar with Benedict’s reagent (and found none)
We tested for starch with iodine (and found some)
2. How do you know that any sugar in your tubes was produced by breaking down starch?
The solution contained no sugar to start with
Solutions which contained sugar contained no starch
3. How do you know that heating the starch at 35⁰C would not break down starch without the amylase?
Heating starch without amylase produced no effect...
... the starch did not disappear and no sugar was produced

7. 4. What happens to the amylase enzyme if you boil it before use?
It stops working (it is destroyed or ‘denatured’)
The starch is not broken down
5. What evidence do you have that saliva contains the enzyme amylase?
When you heat starch with saliva, the starch disappears and sugar is produced, so...
... something in saliva breaks down starch into sugar.
This effect is lost of you boil the saliva first

8. 6. What term describes the experiments with the unboiled enzyme?
Positive controls
7. What term describes the experiments without amylase or saliva?
Negative controls

9. What you need to know:
How do we know that amylase digests starch to produce sugar?
How do we know that saliva contains amylase?
How do scientists solve complicated problems?