Edexcel IGCSE Biology 2.10 enzymes as biological catalysts

Practise enzymes as catalysts by linking concentration, active sites, controlled variables and oxygen-volume data in practicals.

Exam points

State enzymes are biological catalysts and link higher enzyme concentration to more active sites.
Interpret oxygen-volume data as enzyme concentration or potato disc number changes.
Choose control variables such as temperature, pH or potato type in enzyme practicals.

[Maximum number: 1]

Catalase is an enzyme found in many cells.
This enzyme controls the breakdown of hydrogen peroxide into water and oxygen.

2 \mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}

hydrogen water oxygen peroxide

A teacher uses this method to investigate the effect of pH on catalase.
Step 1 cut a cylinder of potato tissue into six equal sized discs
Step 2 measure $10 \mathrm{~cm}^{3}$ of hydrogen peroxide solution and place into a boiling tube
Step 3 add a pH buffer solution to the tube to keep the pH at 7
Step 4 add the six potato discs to the boiling tube
Step 5 collect the gas given off by the reaction in an inverted $20 \mathrm{~cm}^{3}$ measuring cylinder

Step 6 measure the total volume of gas collected after five minutes
Repeat steps 1 to 6 using four different pH buffers ( pH 4, pH 5, pH 6 and pH 8 ).
The diagram shows the teacher's apparatus.

Figure for Question 2.10 Enzymes as biological catalysts question 1 — Edexcel IGCSE Biology

State what is meant by the term enzyme.

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2.10 Enzymes as biological catalysts question 1