(a)
Explain why lipase cannot be used to catalyse the breakdown of proteins.
[ 3 ]
(a)
Yeast cells make the enzyme sucrase. Sucrase catalyses the breakdown of sucrose to glucose and fructose.
Enzymes are made of protein.
Explain how the shape of a sucrase molecule is related to its function.
[ 2 ]
(b)
The students made an extract of sucrase from yeast cells.
They investigated the activity of the sucrase extract at different pH values. They determined the rate of reaction at each pH .
They then calculated the rate of each reaction as a percentage of the fastest reaction, to give the percentage activity of sucrase.
The results of this investigation are shown in Fig. 1.2.
Fig. 1.2
Describe and explain the effect of pH on the activity of sucrase shown in Fig. 1.2.
[ 6 ]
[Maximum number: 8]
Enzymes are catalysts.
(a)
(i)
Describe what is meant by the term catalyst.
[ 2 ]
(b)
Lipase is an enzyme found in the human digestive system.
Fig. 1.1 shows the effect of pH on the percentage activity of lipase.
Fig. 1.1
Describe and explain the change in percentage activity of lipase shown on Fig. 1.1.
[ 6 ]
[Maximum number: 7]
Enzymes are used in genetic engineering.
(a)
Define the term enzyme.
[ 2 ]
(b)
The process of genetic engineering often starts with the steps shown in Fig. 1.1.
Fig. 1.1
[ 2 ]
(i)
Explain how enzyme 1 in Fig. 1.1 is specific to the exact sequence of DNA bases.
[ 2 ]
(c)
Sketch a graph to describe how the activity of the enzymes used in genetic engineering would change if the reaction occurred at a range of temperatures from very cold to very hot.
Label the axes with appropriate titles.
Do not use units or a numbered scale.
[ 3 ]
[Maximum number: 6]
Fig. 1.1 shows several villi from the ileum, which is part of the small intestine.
(a)
Many fungi are decomposers that feed on dead plants. The fungi secrete enzymes to digest large molecules.
Students made an extract from a species of fungus. The extract contained digestive enzymes.
The students carried out an investigation to find out if amylase and pectinase were present in the fungal extract.
They made agar plates by filling Petri dishes with agar jelly containing either starch or pectin. They cut four holes of the same size in the agar jelly in each Petri dish.
The holes in each Petri dish contained the same volume of:
A - 1\% amylase solution
B - 1\% pectinase solution
C - distilled water
D - fungal extract. The Petri dishes were kept at for four days. After this time a dye was poured into each dish to stain the areas where starch and pectin remained. Fig. 1.3 shows drawings of the stained agar in the Petri dishes. The clear zones indicate the areas where no starch or pectin remained.
Fig. 1.3
[ 6 ]
(i)
State what conclusions can be made about the enzymes in the fungal extract and give evidence from Fig. 1.3 to support your conclusions.
[ 5 ]
(ii)
The investigation was repeated but at instead of at .
Predict the effect of the lower temperature on the results.
[ 1 ]
[Maximum number: 6]
Biological washing powders contain enzymes that break down food stains.
(a)
Compare the effectiveness of the two washing powders at removing stains.
Use the information in Fig. 2.1 in your answer.
[ 4 ]
(b)
The students suggested that the enzymes in the biological washing powder were denatured at high temperatures.
Explain why enzyme molecules do not function when they are denatured.
[ 2 ]
[Maximum number: 1]
Which statement describes the effect of temperature on enzymes?
A
High temperatures denature enzymes making it difficult for substrate molecules to fit into the active site.
B
High temperatures denature enzymes making it easy for substrate molecules to fit into the active site.
C
Low temperatures denature enzymes making it difficult for substrate molecules to fit into the active site.
D
Low temperatures denature enzymes making it easy for substrate molecules to fit into the active site.
[Maximum number: 1]
The structures of antibodies, DNA molecules and enzymes are specific to their actions.
Which feature of each molecule makes it specific?
antibody
DNA
enzyme
active site
binding site
base order
base order
active site
binding site
base order
binding site
active site
binding site
base order
active site
[Maximum number: 1]
An experiment was carried out to study the effect of temperature on the time taken for protein to be digested by an enzyme.
The table shows the results.
For these results, at which temperature does the enzyme denature?
A
B
C
D
[Maximum number: 1]
The diagram shows a protease molecule catalysing the break down of a protein molecule.
What are the parts labelled P, Q, R and S ?
enzyme
product
substrate
active site
P
Q
R
S
R
S
P
Q
S
P
Q
R
S
R
Q
P