New
New
Year 10
AQA
Higher

The effect of pH on the rate of an enzyme reaction: practical

I can carry out an investigation into the effect of changing pH on the rate of an enzyme reaction.

New
New
Year 10
AQA
Higher

The effect of pH on the rate of an enzyme reaction: practical

I can carry out an investigation into the effect of changing pH on the rate of an enzyme reaction.

Lesson details

Key learning points

  1. Safe use of materials and apparatus.
  2. Accurate measurement of reactants and reagents.
  3. Control of temperature using a water bath or electric heater.
  4. Continuous sampling of reaction mixture and testing with iodine for the presence of starch.
  5. Sampling at accurately timed intervals.

Common misconception

Mistakes are often made when preparing the practical, for instance which samples go into which test tubes, or carrying out the practical, such as exactly when to take the continuous sample.

The correct approach to preparing and completing this method accurately and carefully is discussed throughout, with quick checks at key points and the opportunity to try it for themselves.

Keywords

  • Rate of reaction - How fast a chemical reaction occurs.

  • PH - A measure of how acidic or alkaline a solution is.

  • Amylase - An enzyme that breaks down starch into maltose (a type of sugar).

  • Starch - A carbohydrate, which is a polysaccharide (a polymer of sugar).

  • Continuous sampling - A method that involves taking regular and frequent samples.

If time is an issue, split the class into three and give each a different pH buffer. Demonstrate the method or show the video so there is no uncertainty in how to proceed and students can carry the practical out confidently.
Teacher tip

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
What is starch made of?
amino acids
Correct answer: sugars
fatty acids
glycerol
Q2.
What is the enzyme that catalyses the breakdown of starch into maltose?
Correct Answer: Amylase
Q3.
Match the variable to its description for the investigation 'Investigating the effect of changing pH on the rate of enzyme reaction'.
Correct Answer:pH,independent variable

independent variable

Correct Answer:enzyme amount,control variable

control variable

Correct Answer:rate of reaction,dependent variable

dependent variable

Q4.
Is this a positive or negative test for starch?
An image in a quiz
Correct answer: positive
negative
Q5.
Who best describes what rate of reaction is?
Sofia: How much substrate has been used up.
Alex: How much enzyme has been used.
Izzy: How much product was formed when the reaction finished.
Correct answer: Jacob: How much product was formed every second.
Q6.
Order these steps to show how you would carry out an investigation into the effect of changing temperature on the rate of an enzyme-controlled reaction.
1 - Measure 5 ml of starch and amylase solution into separate test tubes.
2 - Place both test tubes in a water bath at 21 °C for five minutes.
3 - Combine the solutions and mix gently. Return to the water bath.
4 - Using a pipette, remove a sample of solution.
5 - Test the solution in a spotting tile with iodine solution.
6 - Continue testing every minute until the iodine solution stays orange/brown.
7 - Repeat at different temperatures.
Q4 UYSEG

6 Questions

Q1.
Which piece of equipment would you use in this practical to heat the test tubes of starch and amylase to a specific temperature?
Correct answer: water bath
Bunsen burner
autoclave
hot plate
microwave
Q2.
What is collecting data at accurately timed intervals know as?
random sampling
occasional sampling
Correct answer: continuous sampling
Q3.
What is formed when amylase digests starch?
Correct answer: maltose
proteins
lipids
amino acids
Q4.
What is this piece of equipment called?
An image in a quiz
Correct Answer: Pipette, Pasteur pipette, Dropper pipette
Q5.
Iodine solution is an irritant. What piece of safety equipment should be warn when using it?
Correct Answer: Safety glasses, Glasses, Saftey glasses, Goggles, Safety goggles
Q6.
What is this piece of equipment used for?
An image in a quiz
mixing liquids
Correct answer: measuring liquids
sampling

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