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Proteins and enzymes homework 2
1. An investigation was carried out into digestion of a protein. The protein was mixed with agar
gel in a petri dish. Four holes were cut in the gel and a different enzyme was placed in each
hole. The dish was left for two days. Where digestion of the protein had taken place, a clear
area developed in the gel around the hole. The diameter of the clear area was measured. The
experiment was carried out four times.
The diagram below represents the appearance of one of the petri dishes after two days.
a) What name is given to the substance an enzyme acts upon?
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b) Explain why trypsin digested the protein but no other enzyme did.
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The table below shows the results for each dish.
c) Complete the table by calculating the average diameter of the clear area.
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d) Give two precautions, not already mentioned, that would have to be taken each time the
experiment was carried out, to ensure validity of the results.
1. ________________________________________________________________________
2. ________________________________________________________________________
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2. The apparatus shown below was used to study the effect of different temperatures on the
activity of the enzyme catalase.
The catalase was added and reacted with the hydrogen peroxide to release oxygen. The
increase in oxygen compared to the starting value was recorded as a percentage. This was
carried out at five different temperatures and the results are shown below.
a) At which temperature was the catalase most active?
_________________°C
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b) What word is used to describe the temperature at which an enzyme works best?
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c) Why was it important that the catalase and hydrogen peroxide were both at the required
temperature before the catalase was added?
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d) Explain why there was no oxygen released when the experiments were repeated with
different enzymes.
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e) Calculate the simple whole number ratio of % increase in oxygen at 34 °C, 40 °C and 50 °C.
____________ : ____________ : ____________
34 °C
40 °C
50 °C
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