CIE iGCSE Co-Ordinated Science B5. Enzymes Exam Style Questions Paper 1
Question
Which type of molecule are enzymes?
A. Fat
B. Carbohydrate
C. Protein
D. DNA
▶️Answer/Explanation
Answer: C
Explanation: Enzymes are biological catalysts made up of proteins. They speed up chemical reactions in the body without being consumed in the process.
Question
What is an enzyme?
A. a carbohydrate that speeds up the rate of a reaction
B. a carbohydrate that alters the activity of a target organ
C. a protein that alters the activity of a target organ
D. a protein that speeds up the rate of a reaction
▶️Answer/Explanation
Answer: D
Explanation: Enzymes are biological catalysts made of proteins that speed up chemical reactions in the body without being consumed in the process.
Question
Which graph shows the effect of pH on the rate of activity of an enzyme?
A. rate of enzyme activity increases linearly with pH
B. rate of enzyme activity decreases linearly with pH
C. rate of enzyme activity increases to a maximum and then decreases
D. rate of enzyme activity remains constant with pH
▶️Answer/Explanation
Answer: C. rate of enzyme activity increases to a maximum and then decreases
Explanation: Enzymes have an optimal pH at which they function most efficiently. As pH deviates from this optimal value, the enzyme’s activity decreases. Therefore, the graph showing the rate of enzyme activity increasing to a maximum and then decreasing with pH is correct.
Question
A student carried out an investigation on the effect of temperature on an enzyme-controlled reaction. The results are shown.
Which labels does the student need to add for the axes labelled axis 1 and axis 2?
| Axis 1 | Axis 2 |
|---|---|
| A. rate of reaction | temperature |
| B. rate of reaction | time |
| C. temperature | rate of reaction |
| D. time | rate of reaction |
▶️Answer/Explanation
Answer: C. temperature (Axis 1) and rate of reaction (Axis 2)
Explanation: In an enzyme-controlled reaction, the independent variable (temperature) is typically plotted on the x-axis (Axis 1), and the dependent variable (rate of reaction) is plotted on the y-axis (Axis 2).
Question
A student investigated the effect of pH on an enzyme that digests starch. Which chemical will be needed to determine if any starch has been digested?
A. Benedict’s solution
B. biuret solution
C. iodine solution
D. ethanol
▶️Answer/Explanation
Answer: C. iodine solution
Explanation: Iodine solution is used to test for the presence of starch. If starch is present, the solution turns blue-black. If starch has been digested, the solution will remain brown.
Question
The Pompeii worm lives in deep-sea hydrothermal vents where average temperatures are often as high as 68 C.
Which graph represents the activity of enzymes found in the Pompeii worm?
▶️Answer/Explanation
Ans :B
Question
Catalase is an enzyme that breaks down hydrogen peroxide to form a foam of water and oxygen.
The maximum height of the foam produced at different temperatures in a given length of time is measured.
The rate of the reaction is proportional to the height of foam.
The table shows the results.
Which conclusion can be drawn from these results?
A Increasing the temperature decreases the rate of the reaction up to 50 ºC.
B Increasing the temperature decreases the rate of the reaction up to 60 ºC.
C Increasing the temperature increases the rate of the reaction up to 40 ºC.
D Increasing the temperature increases the rate of the reaction up to 50 ºC.
▶️Answer/Explanation
Ans :A
Question
Fungus can live at the base of human hair where the activity of one of its enzymes can cause dry skin.
The graph shows the action of the fungal enzyme at different pH values.
Different shampoos have different pH values.
Which shampoo causes the greatest amount of dry skin?
A pH3 B pH5 C pH7 D pH9
▶️Answer/Explanation
Ans : B
Question
Which process involves enzymes?
(A) absorption
(B) digestion
(C) egestion
(D) ingestion
▶️Answer/Explanation
Ans: B
Question
Which statement about enzymes is correct?
(A) They are made from fat molecules.
(B) They are used up in a reaction.
(C) They speed up reactions.
(D) They are not affected by temperature.
▶️Answer/Explanation
Ans: C
Question
Which elements can be found in an enzyme molecule?
1 carbon
2 nitrogen
3 oxygen
(A) 1, 2 and 3
(B) 1 and 3 only
(C) 1 only
(D) 2 only
▶️Answer/Explanation
Ans : A
Question
The graph shows the rate at which 10 g of starch is broken down by amylase at four different temperatures.
At which temperature does amylase work best to break down starch?
A 10 ºC B 25 ºC C 40 ºC D 70 ºC
▶️Answer/Explanation
Ans : C
Question
Which type of molecules speed up chemical digestion?
A carbohydrates
B enzymes
C hormones
D fatty acids
▶️Answer/Explanation
Ans : B
Question
Which type of molecule are enzymes?
(A) amino acids
(B) carbohydrates
(C) fats
(D) proteins
▶️Answer/Explanation
Ans : D
Question
Which graph is correct?
▶️Answer/Explanation
Ans: B
Question
Which type of molecule are enzymes?
(A) carbohydrate
(B) fat
(C) protein
(D) starch
▶️Answer/Explanation
Ans: C
Question
Which graph shows the effect of temperature on enzyme activity?
▶️Answer/Explanation
Ans : D
Question
The graph shows the effect of pH on two different enzymes.
Which statement is correct?
(A) Both enzymes show no activity in conditions of pH 4.
(B) Both enzymes are active in conditions of pH 5.
(C) Only enzyme X is active in conditions of pH 10.
(D) Only enzyme Y is active in conditions of pH 3.
▶Answer/Explanation
Ans : B
Question
What are biological catalysts?
A. antibodies
B. enzymes
C. hormones
D. platelets
▶️Answer/Explanation
Answer: B
Explanation: Biological catalysts are enzymes, which speed up chemical reactions in living organisms without being consumed in the process. Antibodies are part of the immune system, hormones are chemical messengers, and platelets are involved in blood clotting, so options A, C, and D are incorrect.
Question
A mixture of starch and saliva was set up at four different temperatures. Each mixture was tested with iodine solution after 15 minutes and again after 30 minutes.
The results are shown in the table.
| temperature /°C | colour with iodine solution (15 minutes) | colour with iodine solution (30 minutes) |
|---|---|---|
| 0 | blue-black | blue-black |
| 15 | blue-black | brown |
| 35 | brown | brown |
| 95 | blue-black | blue-black |
What do the results suggest?
A. The enzyme in saliva is inactive at 95°C.
B. The enzyme in saliva is slow to work at 35°C.
C. The enzyme in saliva works equally well at 15°C and 35°C.
D. The enzyme in saliva works faster at higher temperatures.
▶️Answer/Explanation
Answer: A. The enzyme in saliva is inactive at 95°C.
Explanation: The enzyme in saliva (amylase) breaks down starch into simpler sugars. At 95°C, the enzyme is denatured and inactive, as indicated by the blue-black color with iodine solution, which means starch is still present. At 35°C, the enzyme is active, as indicated by the brown color, which means starch has been broken down.
Question
Which graph shows the effect of temperature on the activity of a mammalian enzyme?
▶️Answer/Explanation
Answer: C. Graph C
Explanation: The activity of enzymes increases with temperature up to an optimum point, after which the enzyme denatures and activity decreases. Graph C correctly shows this relationship.
Question
Which smaller molecules make up enzymes?
A. amino acids
B. fatty acids
C. glucose
D. glycerol
▶️Answer/Explanation
Answer: A. amino acids
Explanation: Enzymes are proteins, and proteins are made up of amino acids. Therefore, amino acids are the smaller molecules that make up enzymes.
Question
Which type of molecule is an enzyme?
A. Carbohydrate
B. Fat
C. Protein
D. Vitamin
▶️Answer/Explanation
Answer: C. Protein
Explanation: Enzymes are biological catalysts made up of proteins. They speed up chemical reactions in the body without being consumed in the process.
Question
Which statements are correct for all enzymes?
1. They are proteins.
2. They are unaffected by temperature.
3. They speed up chemical reactions.
4. They work best at a high pH.
A. 1, 2 and 4
B. 1, 3 and 4
C. 1 and 3 only
D. 2 and 4 only
▶️Answer/Explanation
Answer: C. 1 and 3 only
Explanation: Enzymes are proteins that act as biological catalysts, speeding up chemical reactions. However, they are affected by temperature and pH, and each enzyme has an optimal pH at which it works best, which is not necessarily high.
Question
A solution of salivary amylase is boiled in a test tube. The boiled amylase is then added to a solution of starch. Which graph shows what happens to the concentration of starch in the mixture during the next 10 minutes?
▶️Answer/Explanation
Answer: B
Explanation: Boiling denatures the enzyme amylase, rendering it inactive. Therefore, the concentration of starch will remain constant over time as the enzyme cannot break it down.
Question
Which graph shows how enzyme activity is affected by temperature?
▶️Answer/Explanation
Answer: D
Explanation: Enzyme activity increases with temperature up to an optimum point, after which it decreases due to denaturation.
Question
The graph shows the activity of an enzyme at different temperatures.
What is the optimum temperature for this enzyme?
A. 20°C
B. 40°C
C. 60°C
D. 80°C
▶️Answer/Explanation
Answer: C
Explanation: The optimum temperature for an enzyme is the temperature at which it shows the highest activity. In this case, the enzyme’s activity peaks at 60°C, indicating that this is its optimum temperature.
Question
The graphs show the possible effects of temperature on the rate of reaction of an enzyme. Which graph is correct for a human enzyme?
▶️Answer/Explanation
Answer: A
Explanation: Human enzymes typically have an optimal temperature around 37°C. The rate of reaction increases with temperature up to this point, after which the enzyme denatures, and the rate drops sharply. Graph A correctly represents this behavior.