Rates of Enzyme-Controlled Reactions: Development of Practical Skills in Biology: Biology OCR A Level

What are the four factors affecting rate of enzyme reaction?

Enzyme concentration
Substrate concentration
Temperature
pH

How can you measure the rate of reaction using hydrogen peroxide and catalase?

Measure the volume of oxygen gas produced in a given time

State the word equation for the action of catalase.

Hydrogen peroxide → Oxygen + Water

What are the controlled variables of this practical?

Enzyme volume and concentration
Substrate volume and concentration
pH

State the hazards and safety precautions involved in this practical.

Hydrogen peroxide is an irritant.
Wear eye protection and avoid contact with skin.
Take care in handling hot water baths, and wash hands after handling peas/ source of catalase.

Outline the procedure to find the effect of enzyme concentration on rate of reaction using amylase.

1. Put drops of iodine solution into each well of a spotting tile.
2. Make a serial dilution of amylase to produce several concentrations.
3. Add the same concentration and volume of starch to the first boiling tube. At the same time, start the timer.
4. Use a dropping pipette to put a drop of this mixture into one of the wells containing the iodine solution at regular intervals.
5. Time how long it takes for the colour to no longer turn blue-black.
6. Repeat at least 2 more times and calculate the mean time taken.
7. Repeat the experiment for each concentration of amylase.

What are the controlled variables of this practical?

Temperature
pH
Substrate volume and concentration
Volume of enzyme added