IB Biology SL C1.1 Enzymes and metabolism Questions

Practise IB Biology SL C1.1 by explaining enzyme specificity, metabolic reactions and rate evidence from temperature, pH and substrate experiments.

67 questions in this syllabus scope, with question parts counted together.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam analysis

SL · 2010–2025
Papers with this topic68 / 141in the analysed sample
Latest appearanceNovember 2025
Tagged question parts89
Paper types5

Most tested objectives

  1. C1.1.8—Effects on enzyme activity36 papers
  2. C1.1.3—Anabolic and catabolic reactions12 papers
  3. C1.1.9—Measuring enzyme reactions9 papers
  4. C1.1.5—Induced-fit binding6 papers
  5. C1.1.7—Relationships between structure and function4 papers

Common question formats

  • Calculation
  • Data analysis
  • Definition or recall
  • Diagram interpretation
  • Experimental design
  • Extended response
  • Graph interpretation
  • Structured response

Recent exam appearances

November 2025Paper 1B SL · TZ1Q3(a), 3(d)[ 4 ]
November 2025Paper 1A SL · TZ1Q4[ 1 ]
May 2025Paper 1B SL · TZ3Q4(c), 4(d), 4(e)[ 5 ]

141 papers analysed · Tagging incomplete

Exam points

  • Identify enzyme-catalysed steps in metabolism and classify reactions as anabolic or catabolic, including condensation, hydrolysis and oxidation.
  • Relate enzyme tertiary structure and active-site shape to substrate specificity, comparing lock-and-key and induced-fit binding.
  • Explain how temperature and pH change enzyme activity through molecular collisions, active-site bonding and denaturation.
  • Interpret enzyme activity data for temperature, pH and substrate concentration; identify optima and saturation and calculate rates.
  • Choose suitable measurements, controls and repeats to calculate enzyme activity and evaluate assay reliability.
  • Interpret enzyme-catalysed energy profiles to identify reduced activation energy with unchanged reactant and product energies.

Covered syllabus points

C1.1.1—Enzymes as catalystsC1.1.2—Role in metabolismC1.1.3—Anabolic and catabolic reactionsC1.1.4—Enzymes as globular proteinsC1.1.5—Induced-fit bindingC1.1.6—Molecular motionC1.1.7—Relationships between structure and functionC1.1.8—Effects on enzyme activityC1.1.9—Measuring enzyme reactionsC1.1.10—Effect of enzymes on activation energy

Exam points

  • Define enzymes as biological catalysts; most are proteins, although some RNA molecules are catalytic.
  • Explain that enzymes act in small amounts and remain unchanged after catalysis.

No public sample questions are available for this syllabus point yet.

Exam points

  • Define metabolism as the complete set of enzyme-controlled chemical reactions in cells.
  • Explain that specific enzymes determine which metabolic reactions occur and when.

Question 1

[Maximum number: 1]

Which enzyme is matched to its function?

Enzyme

Function

helicase

forms a DNA helix

DNA polymerase

forms a covalent bond between DNA nucleotides

restriction endonuclease

seals nicks in recombinant DNA

ligase

unwinds the double helix

Exam points

  • Explain how anabolism builds complex molecules by condensation and requires energy.
  • Explain how catabolism breaks molecules by hydrolysis or oxidation and releases energy.

Question 1

[Maximum number: 1]

Which process is an example of catabolism?

A

Protein synthesis

B

Photosynthesis

C

Oxidation of substrates in respiration

D

Glycogen formation

Exam points

  • Describe enzymes as usually globular proteins with a small active-site pocket that binds a substrate.
  • Explain that binding forms an enzyme–substrate complex and allows the reaction to be catalysed.

Question 1

[Maximum number: 1]

The image represents the structure of the enzyme Rubisco from common pea (Pisum sativum).

Figure for Question 1 — IB Biology SL

State a role of the active site of an enzyme.

Exam points

  • Explain that substrate binding induces shape changes in both the enzyme and substrate.
  • Explain how induced fit aligns catalytic groups and raises the substrate towards the transition state.

Question 1

[Maximum number: 1]

The diagram shows the formation of an enzyme-substrate complex.

Figure for Question 1 — IB Biology SL

What describes the process shown in the diagram?

A

The lock and key hypothesis, as the substrate is complementary to the enzyme.

B

The substrate permanently alters the shape of the enzyme's active site.

C

The substrate and the active site have the same shape.

D

The active site changes shape to accommodate the substrate in the induced-fit model.

Exam points

  • Explain how random molecular motion brings substrates into collisions with enzyme active sites.
  • Explain how higher kinetic energy increases the chance of successful substrate–active-site collisions.

Question 1

[Maximum number: 1]

Which statement applies to enzymes?

A

Enzyme function depends on collisions between substrate and active sites.

B

One active site typically binds to a broad range of substrates.

C

The active site on the substrate is specific to one enzyme.

D

When enzymes are immobilized they stop working.

Exam points

  • Explain how active-site amino acid arrangement determines substrate specificity.
  • Explain how denaturation changes tertiary structure and active-site shape without breaking peptide bonds.

Question 1

[Maximum number: 3]

Explain enzyme-substrate specificity.

Exam points

  • Explain how increasing temperature raises enzyme activity to an optimum, after which denaturation lowers the rate.
  • Explain how pH changes alter bonding at the enzyme active site and affect enzyme activity.
  • Interpret substrate-concentration data to explain the rise in enzyme activity to a saturation plateau.

Question 1

[Maximum number: 2]

A scientist investigated the effect of storage temperature on the activity of an enzyme.

The scientist incubated three lipase solutions for one hour at three different storage temperatures (40∘C,50∘C\left(40^{\circ} \mathrm{C}, 50^{\circ} \mathrm{C}\right. or 60∘C)\left.60^{\circ} \mathrm{C}\right).

At every 10-minute interval, a sample of lipase solution was taken and immediately used to catalyse the digestion of a small volume of oil. The values were then compared to the results obtained at the optimum temperature for lipase ( 37∘C37^{\circ} \mathrm{C} ). Relative enzyme activity values were determined.

The graph shows the mean results of the investigation.

Figure for Question 1 — IB Biology SL

Explain the relationship shown between storage temperature and relative enzyme activity.

Exam points

  • Measure enzyme activity as substrate loss or product formation per unit time.
  • Use an initial rate from amylase or catalase assay graphs to compare enzyme activity.
  • Use replicates and controlled variables when measuring enzyme reactions to assess result reliability.

Question 1

[Maximum number: 4]

Protease enzymes break down (degrade) protein. The catalytic activity of the protease enzymes papain and bromelain on meat tenderization was evaluated by injecting the enzymes at different concentrations into beef. Meat tenderization was assessed by measuring the concentration of the amino acid tyrosine, which is released from proteins as they become degraded. The graph shows the effect of enzyme concentration after 24 and 48 hours.

Figure for Question 1 — IB Biology SL

Question (a)

(a)

State an independent variable in this experiment.

[ 1 ]

Question (b)

(b)

Justify the use of the concentration of amino acids, such as tyrosine, to assess protease enzyme activity.

[ 3 ]

Exam points

  • Explain that enzymes lower activation energy by providing an alternative reaction pathway.
  • Explain how enzyme binding stabilises the transition state, lowering activation energy and increasing reaction rate.

Question 1

[Maximum number: 4]

Outline the action of enzymes.

Question 1

[Maximum number: 3]

The image represents the structure of the enzyme Rubisco from common pea (Pisum sativum).

Figure for Question 1 — IB Biology SL

Question (a)

(a)

State a role of the active site of an enzyme.

[ 1 ]

Question (b)

(b)

Outline one factor that could affect the activity of Rubisco.

[ 2 ]
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