Author: Christ the King
Last saved by: Daniel Wilson

Enzymes homework 2    (     /30)

Q1. Proteins, such as enzymes, are important molecules found in all living organisms.

(a) Read through the following passage on the primary structure of proteins, then write on the dotted lines the most appropriate word or words to complete the passage.
(5)
 Proteins are made of monomers called ........................................................... These monomers
are joined together by ............................................................................................. bonds, formed during
............................................................................................. reactions.
Each monomer of a protein consists of a central carbon atom attached to a hydrogen
atom, an R group, an ............................................................................................. group and
a ............................................................................................. group. The sequence of monomers determines the primary structure of the protein.

(b) (i) Describe the three-dimensional (tertiary) structure of an enzyme.
(3)
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(ii) Explain how the primary structure of an enzyme determines its three-dimensional (tertiary) structure and its properties. (3)
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Q2. Enzymes are biological catalysts that change the activation energy of chemical reactions.
(a) Explain the meaning of the terms biological catalyst and activation energy. (4)
Biological catalyst
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Activation energy
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 (b) The graph below shows the results of an investigation into the effect of enzyme concentration on the initial rate of this reaction.

Explain why it is necessary to measure the initial rate of reaction when investigating the effect of enzyme concentration on the rate of reaction. (2)
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(c) In this investigation, the substrate concentration was a factor that was kept constant.
 Suggest two other factors that should be kept constant. For each factor, state how it can be kept constant. (4)
Factor 1
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How the factor can be kept constant
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Factor 2
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How the factor can be kept constant
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(Total for question = 10 marks)

Q3.A student investigated the effect of lipase concentration on the hydrolysis of lipids.He took a beaker containing a suspension of lipids. He placed a pH probe attached to a data logger into the beaker. After 5 minutes, he added the lipase solution. The data logger recorded the pH. The apparatus used is shown in the diagram below.
 
(a)     The student did not add a buffer to the lipase solution.Explain why.
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___________________________________________________________________(1)
(b)     Give two variables the student would have controlled in this investigation.
1. _________________________________________________________________
2. _________________________________________________________________(2)
(c)     Give the suitable control for this investigation.
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The data logger recorded the pH. The graph below shows what happened after he added the lipase solution.
 
(d)     Draw a tangent on the graph and use it to calculate the rate of change at 5 minutes.
Rate of change at 5 minutes = _________________ pH minute^−1(2)
(e)     Explain the results shown in the graph.
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___________________________________________________________________ (2)
(f)      The student repeated the experiment with a higher concentration of lipase solution.
Describe and explain the results you would expect him to get.
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___________________________________________________________________(3)

Carmel College