Enzymes — IGCSE Biology (0970) questions by topic
Enzyme questions interpret a biological washing powder label listing protease and lipase, read a temperature-against-activity graph peaking near 40 degrees Celsius before falling to zero, compare four test-tubes testing lipase's breakdown of milk fats with and without boiling, and judge whether an active site's shape matches a substrate or all proteins.
Choose, state, describe, explain and identify lead 26 real questions worth 1 to 12 marks from 2023 to 2025 papers. Because these questions often ask for the shape and effect of denaturation rather than a general enzyme description, submitting each answer for instant marking shows precisely where the specificity of the active site or the temperature effect has been described too loosely.
May–June 2025, Paper 11
The graph shows the activity of three digestive enzymes at differing pH values. Enzyme X has a peak of activity at a low pH (around pH 2-3) and is active roughly between pH 1 and…
Answer this question and get it marked →May–June 2025, Paper 21
The graph shows how enzyme activity is affected by temperature. The curve rises from a low value at 0 °C, increases to a peak at around 40 °C, then falls steeply to zero at about…
Answer this question and get it marked →May–June 2025, Paper 22
What is the correct definition of enzymes? A carbohydrates that act as biological catalysts B carbohydrates that act as substrates C proteins that act as biological catalysts D…
Answer this question and get it marked →May–June 2025, Paper 42
A scientist investigated the effect of changes in pH on the activity of two different protease enzymes. Each enzyme was placed in a hole in the centre of a jelly layer in a Petri…
Answer this question and get it marked →May–June 2024, Paper 11
What is a correct statement about enzymes? A The pH has no effect on the rate of reaction. B They are denatured at low temperatures. C They are made of carbohydrates which have…
Answer this question and get it marked →Which statement about enzyme action is correct? A The shape of the enzyme's active site is complementary to all proteins. B The shape of the enzyme's active site is complementary…
Answer this question and get it marked →May–June 2024, Paper 12
Which graph (A–D) shows the effect of temperature on the activity of an enzyme? Each graph plots enzyme activity against temperature (0–100 °C). A B C D
Answer this question and get it marked →Which of these statements about enzymes are correct? 1 enzymes are proteins 2 enzymes are used up during chemical reactions 3 enzymes speed up metabolic reactions A 1, 2 and 3 B 1…
Answer this question and get it marked →The diagram shows a label on a container of biological washing powder: works at low temperatures; contains protease; contains lipase; keep out of reach of children. The table…
Answer this question and get it marked →May–June 2024, Paper 21
A student investigates the breakdown of fats in milk by lipase. Four test-tubes A–D are set up. The table shows the contents (key: ✓ = present, ✗ = absent): A: milk ✓, bile ✓,…
Answer this question and get it marked →May–June 2024, Paper 22
The graph shows the effect of pH on the rate of an enzyme-catalysed reaction (rate against pH 0–10). What explains the effect of pH on the reaction rate? A As the pH increases…
Answer this question and get it marked →May–June 2024, Paper 31
Enzymes are biological catalysts. Describe what is meant by a catalyst.
Answer this question and get it marked →May–June 2024, Paper 41
A student investigated the effect of lactase on three different liquids: milk, lactose-free milk and sucrose solution. The student used an indicator to test for glucose (brown in…
Answer this question and get it marked →October–November 2024, Paper 12
Which statements about enzymes are correct? 1 Enzymes are biological catalysts. 2 Enzymes are carbohydrates. 3 Enzymes have an active site.
Answer this question and get it marked →October–November 2024, Paper 22
The diagram shows the steps in an enzyme-controlled reaction. Substrate binds to enzyme active site forming a complex labelled X, then products are released. What describes the…
Answer this question and get it marked →The graph shows the effect of temperature on the time taken for the complete digestion of starch. The curve shows shortest time (fastest rate) at around 40°C. At which temperature…
Answer this question and get it marked →October–November 2024, Paper 32
Tick (✓) all the boxes that describe enzymes. Statement --- they are permanently changed by the reaction they are involved in all metabolic reactions they are proteins they are…
Answer this question and get it marked →May–June 2023, Paper 11
What is true of all enzymes? The table considers two statements: they are sugars; they are most effective at pH 7 (key: shaded = yes, blank = no). A B C D
Answer this question and get it marked →The diagram shows enzyme X with a labelled active site and four molecules A, B, C and D of differing shapes. What is the substrate for enzyme X? A B C D
Answer this question and get it marked →May–June 2023, Paper 12
Which processes depend on the action of enzymes? 1 digestion 2 osmosis 3 respiration A 1 and 2 B 1 and 3 C 1 only D 2 and 3
Answer this question and get it marked →Which diagram of an enzyme, active site and substrate is correct? Diagrams A–D show an enzyme with an active site and a substrate, with differing shape matches between the active…
Answer this question and get it marked →May–June 2023, Paper 21
What is true of all enzymes? The table considers two statements: they are sugars; they are most effective at pH 7 (key: shaded = yes, blank = no). A B C D
Answer this question and get it marked →Which statement about human enzymes is correct when they are at temperatures above 80 °C? A The enzyme molecules are denatured. B The shape of the active site is stable. C More…
Answer this question and get it marked →May–June 2023, Paper 22
The graphs A–D show the effect of temperature on enzyme activity. This enzyme has an optimum temperature of 30 °C. Which graph shows the effect of temperature on the activity of…
Answer this question and get it marked →May–June 2023, Paper 32
Fig. 3.1 shows the action of an enzyme. On Fig. 3.1 use label lines and labels to identify: • an enzyme • a product • a substrate.
Answer this question and get it marked →October–November 2023, Paper 12
Which changes could cause an enzyme to denature? 1 change in pH 2 change in temperature 3 change in substrate concentration A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3…
Answer this question and get it marked →Other IGCSE Biology topics
- Human nutrition (75)
- Organisms and their environment (64)
- Coordination and response (62)
- Reproduction (53)
- Organisation of the organism (cells) (50)
- Plant nutrition (42)
- Characteristics and classification of living organisms (40)
- Variation and selection (40)
- Transport in animals (39)
- Inheritance (39)
- Movement into and out of cells (38)
- Transport in plants (38)