Pearson Edexcel International GCSE in Biology · 4BI1 · Free · no account needed
Enzymes and pH — exam questions
9 original Incandio exam-style questions on enzymes and pH, 19 marks, about 19 minutes of writing. Each one carries the command word, the tariff and the specification statement it assesses, exactly as a paper presents them. This is an original Incandio practice question, written to reflect the structure and demands of the qualification. It is not an official Pearson Edexcel past-paper question.
This is the practice set for Enzymes and pH — the lesson that teaches it. Read the lesson first if the idea is new; come here when you want to find out whether you can turn it into marks. Completely free, no account needed to read.
What these questions ask of you
7 command words run through this set, and on Pearson Edexcel International GCSE Biology each one means something precise. Answering the wrong command is the commonest way a candidate who understands the lesson still loses the mark.
- Which (1 mark)
- one option chosen from the set given
- Name (1–2 marks)
- the correct term, spelled recognisably
- State (1 mark)
- one precise fact, no justification
- Explain (2–4 marks)
- a causal chain — WHY it happens, each link a separate marking point Misread as: describing what happens without giving the reason it happens
- Describe (2–4 marks)
- developed, linked statements of WHAT happens — no reason required, but detail is Misread as: giving one bare statement where the tariff asked for a developed account
- Suggest (1–3 marks)
- a plausible answer applying taught biology to a situation not taught
- Give (1–2 marks)
- a short factual answer drawn from recall or from the data
Assessed on Paper 1 (4BI1/1B) and Paper 2 (4BI1/2B), against AO1, AO2, AO3.
Where these sit in the specification
Pearson Edexcel International GCSE Biology (4BI1) — statements 2.13 · 2.14. Incandio is aligned to this specification; it is not published by, endorsed by or affiliated with Pearson, and it reproduces none of Pearson's wording.
The 9 questions
Answer them on paper, then open the lesson's exam practice to have them marked. The mark scheme, the accepted and rejected answers and the annotated model answer are in Incandio and are not printed here — an answer beside its question is not practice.
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Figure 1 — the rate of reaction of enzyme X at different pH values. Plotted as a line; the graph is drawn in Incandio and the readings are below. pH Rate of reaction / arbitrary units 2 0 3 2 4 8 5 20 6 38 7 46 8 34 9 12 10 1 Figure 2 — the rate of reaction of enzyme Y at different pH values. Plotted as a line; the graph is drawn in Incandio and the readings are below. pH Rate of reaction / arbitrary units 1 14 2 41 3 30 4 12 5 3 6 0 7 0 (a)
(1)Give
Give the optimum pH of enzyme X, using Figure 1.
Figure 1 — the rate of reaction of enzyme X at different pH values. Plotted as a line; the graph is drawn in Incandio and the readings are below. pH Rate of reaction / arbitrary units 2 0 3 2 4 8 5 20 6 38 7 46 8 34 9 12 10 1 Figure 2 — the rate of reaction of enzyme Y at different pH values. Plotted as a line; the graph is drawn in Incandio and the readings are below. pH Rate of reaction / arbitrary units 1 14 2 41 3 30 4 12 5 3 6 0 7 0 optimum pH of enzyme X = ............................
(b)
(3)Explain
Explain the shape of the curve for enzyme X between pH 7 and pH 10.
Figure 1 — the rate of reaction of enzyme X at different pH values. Plotted as a line; the graph is drawn in Incandio and the readings are below. pH Rate of reaction / arbitrary units 2 0 3 2 4 8 5 20 6 38 7 46 8 34 9 12 10 1 Figure 2 — the rate of reaction of enzyme Y at different pH values. Plotted as a line; the graph is drawn in Incandio and the readings are below. pH Rate of reaction / arbitrary units 1 14 2 41 3 30 4 12 5 3 6 0 7 0 (c)
(2)Suggest
Suggest where in the human digestive system enzyme Y is most likely to act, using Figure 2.
Figure 1 — the rate of reaction of enzyme X at different pH values. Plotted as a line; the graph is drawn in Incandio and the readings are below. pH Rate of reaction / arbitrary units 2 0 3 2 4 8 5 20 6 38 7 46 8 34 9 12 10 1 Figure 2 — the rate of reaction of enzyme Y at different pH values. Plotted as a line; the graph is drawn in Incandio and the readings are below. pH Rate of reaction / arbitrary units 1 14 2 41 3 30 4 12 5 3 6 0 7 0 (Total for Question 1 = 6 marks)
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(1)Which
Which pH is the optimum for the protease released into the human stomach?
pH A pH 2 B pH 7 C pH 9 D pH 12 (Total for Question 2 = 1 mark)
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(1)Name
Name the process by which an enzyme permanently loses its shape at an extreme pH.
(Total for Question 3 = 1 mark)
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(1)State
State what is meant by the optimum pH of an enzyme.
(Total for Question 4 = 1 mark)
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(4)Explain
Explain why an enzyme stops working when the pH is moved far below its optimum.
(Total for Question 5 = 4 marks)
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(3)Describe
Describe how a buffer solution would be used in an investigation into the effect of pH on an enzyme, and why it is needed.
(Total for Question 6 = 3 marks)
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(3)Suggest
An enzyme extracted from bacteria living in an alkaline soda lake has an optimum of pH 10. Suggest why this enzyme is used in washing powders.
(Total for Question 7 = 3 marks)
Have them marked, then defend the answer
Practice tells you the mark; teaching it back tells you whether you understand it. On Incandio a topic counts as mastered only once you have taught it and defended it.
- Mark these questions — 9 questions, marked on Incandio against the authored scheme, with the mistake you actually made named.
- Teach it — explain enzymes and pH to Ember, an AI pupil who does not have it yet and asks the awkward question.
- Defend it — argue it against Søren Sørensen over three rounds, marked against descriptors you can read first.
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Back to the lesson
- Enzymes and pH — Why acid ruins one enzyme and is the only condition another will work in — and how to find an enzyme's best pH by experiment.
- All of Incandio Biology · Incandio Exam Practice