Explain DNA controlling cell reactions through enzyme proteins
DNA controls function through protein production. For an enzyme: coding information → enzyme protein → catalysed reaction. Binding, amount and activity conditions must be supplied before claiming a specific rate.
Exam scope and assessment notes
Extended only (Supplement) · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall the nucleus, DNA base pairing, gametes, fertilisation, enzymes, membrane carriers and chemical synapses.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which protein example connects DNA with control of reaction rate?
What you will learn
- Connect gene information with an enzyme and its reaction role
- Use the supplied binding conditions rather than a guaranteed effect
Original teaching model. Counts and records are stipulated; drawings are schematic.
| Feature | Meaning |
|---|---|
| Information | Gene coding for an enzyme |
| Product | Enzyme protein with a folded shape |
| Function | Catalyses a cell reaction |
| Evidence limit | Presence is not a measured activity rate |
Connect gene information with an enzyme and its reaction role
DNA controls cell function partly by controlling the production of proteins. Enzymes are one required example: a protein-coding gene provides information used to make an enzyme, and the enzyme catalyses a cell reaction. The DNA does not itself sit in the reaction as the enzyme. Information, protein production and reaction role are connected but different stages.
An enzyme’s amino-acid sequence influences its folded shape, including the active-site region. A suitable active-site shape permits the specified substrate interaction. This links the gene and protein sequence with the earlier enzyme lessons, without claiming every amino-acid change necessarily abolishes all activity or that all enzyme reactions use one identical shape.
Use the supplied binding conditions rather than a guaranteed effect
An original model stipulates enzyme E binds substrate S and helps its conversion to product P under the stated conditions. A second outline is stipulated not to bind S. Under that evidence, the second outline cannot carry out the same model binding step. The drawing alone is not enough to make that prediction unless the binding condition is actually supplied.
A gene can be present while the relevant enzyme is not currently produced at the required amount. Likewise, an enzyme can be present while conditions limit its activity. Do not collapse gene presence, protein amount and measured reaction rate into one observation. The practice traces a defined information-to-function chain rather than diagnosing a person or estimating an unprovided cellular rate.
Pause and explain
A model stipulates a changed outline cannot bind S. What follows within that model?
Worked example
In the supplied E–S model, why does the gene not act as the enzyme itself?
Show the worked solution
- Locate the gene’s coding-information role.
- Identify the protein performing the catalysed-reaction role.
Answer The DNA gene carries information used to produce enzyme E; the enzyme protein, not the gene, acts in the model reaction.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Trace the DNA-to-reaction relationship using an enzyme example.
Give me a hint
Use information, product and function.
Compare my reasoning
- Identify gene information producing an enzyme.
- Connect the enzyme with a catalysed cell reaction.
DNA gene information is used to produce an enzyme protein, which catalyses a cell reaction and so contributes to control of cell function.
Look for these in your work
- Include protein production
- Include reaction role
Explain the stipulated consequence when one model enzyme outline cannot bind substrate S.
Give me a hint
Use the specified binding condition only.
Compare my reasoning
- Identify the absent S-binding step.
- Limit the prediction to that model interaction.
The outline cannot carry out the specified binding interaction with S in this model; it does not establish that every enzyme activity in the cell is lost.
Look for these in your work
- Use the binding evidence
- Keep the prediction bounded
An enzyme gene is present but there is no expression or reaction-rate record. Can its presence establish a measured rate?
Give me a hint
Information availability is not a rate measurement.
Compare my reasoning
- Separate gene presence from enzyme production.
- Identify missing activity and condition evidence.
No. Gene presence does not establish enzyme amount, activity conditions or a measured reaction rate; those observations are missing.
Look for these in your work
- Separate evidence categories
- State missing rate evidence
Common mistakes
- Gene presence does not automatically establish enzyme amount or rate.
- A shape effect must respect the supplied binding evidence.
What can you explain now?
A model stipulates a changed outline cannot bind S. What follows within that model?
Compare with the explanation
That outline cannot perform the specified S-binding step
The conclusion uses supplied binding evidence.
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Make it stick
Explain connect gene information with an enzyme and its reaction role and use the supplied binding conditions rather than a guaranteed effect. Use the stated cell, chromosome sets and information pathway before opening the solutions.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.