Enzymes
Q1.
Amylase is an enzyme found in the human body.
Amylase breaks down starch into sugars.
(a)     Where is amylase produced in the human body?
Tick one box.
 
Liver and pancreas		
Liver and stomach		
Salivary glands and pancreas		
Salivary glands and stomach		
(1)
(b)     Enzymes speed up chemical reactions.
Explain how amylase breaks down starch.
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(3)
(c)     One sugar in the body is glucose.
Glucose is used for respiration.
Give one other use for glucose in the body.
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(1)
(d)     A student investigated the effect of temperature on the activity of human amylase.
This is the method used.
1.   Put 2 cm3 of 1% starch solution into a boiling tube.
2.   Put 2 cm3 of amylase solution into a second boiling tube.
3.   Put both boiling tubes into a water bath at 20 °C.
4.   After 5 minutes, mix the amylase and the starch together in one boiling tube.
5.   After 30 seconds, add a drop of the starch and amylase mixture to a drop of iodine solution in one well of a spotting tile.
6.   Repeat step 5 until the iodine solution no longer changes colour.
7.   Repeat steps 1 – 6 at 40 °C and at 60 °C and at 80 °C
Why did the student leave the starch and amylase solutions in the water bath for 5 minutes in step 3?
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(1)
(e)     The temperature of the human body is 37 °C
The diagram below shows the results of the investigation at 20 °C and at 80 °C
Complete the diagram to show the results you would expect at 40 °C and at 60 °C
You should write a tick or a cross in each well of the spotting tile.
 
(2)
(f)      There are different ways to investigate the breakdown of starch by amylase.
One other method is to measure the concentration of starch present in the solution every 30 seconds.
Why is this method better than the method the student used?
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(2)
A colorimeter can be used to measure the concentration of starch present in the solution every 30 seconds.
A colorimeter measures the amount of light that cannot pass through a solution.
This is known as absorbance.
Below shows a graph of absorbance against concentration of starch.
 
(g)     The absorbance of the solution at 40 °C was 0.56 arbitrary units after 30 seconds.
What was the concentration of starch in this solution?
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Concentration of starch = ____________________ %
(1)
(h)     The concentration of starch in the solution at 20 °C after 1 minute is different from the concentration at 40 °C after 1 minute.
Explain why.
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(2)
(i)      Predict the absorbance for the solution at 80 °C after 30 seconds.
Give a reason for your answer.
Absorbance = ______________________ arbitrary units
Reason ____________________________________________________________
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(3)
(Total 16 marks)