2.1.4 Enzymes – Affect of pH on enzyme action Flashcards
(14 cards)
What is pH?
pH is a measure of the concentration of hydrogen ions present in a solution.
Why does pH have an effect on the rate of enzyme controlled reactions?
Enzymes are affected by changes in pH since the hydrogen ions disrupt the hydrogen bonds and ionic bonds that hold the tertiary structure of the active site in place. This causes the active site to change shape and substrate molecules no longer fit and therefore are unable to form enzyme-substrate complexes.
What is catalase and what does it do?
Catalase is an enzyme in the liver that breaks down harmful hydrogen peroxide into oxygen and water.
Describe one way that the rate of reaction between catalase and hydrogen peroxide can be measured.
The reaction between catalase and hydrogen peroxide produces oxygen. This oxygen can be captured and measured in a measuring cylinder upended in water or with a gas syringe within a time period to calculate rate from formation of product.
Explain why different enzymes are affected by pH changes in different ways.
Different enzymes are affected differently by pH changes since the number of ionic bonds present at the active site differs between enzymes – each enzyme has its own optimum pH.
Give some of the limitations of the method used in class to investigate the effect of pH on the rate of the reaction between hydrogen peroxide and catalase.
- Some gas could be lost from the apparatus and connecting tubes so that a lower volume of gas is collected.
- There could be variations in the time delay in adding the enzyme to each tube will also lead to variations in the volume of gas collected.
Give a definition for accuracy.
A measurement of how close a result is to the true value.
Give a definition for data.
Information, either quantitative or qualitative, that has been collected.
Give a definition for precision.
Measurements which are all close to the mean value.
Give a definition for repeatable.
If the original scientist can repeat their results using the same method.
Give a definition for reproducible.
If a different scientist can repeat the results using different techniques.
Give a definition for validity.
The suitability of the investigation to answer the original question.
How can you measure the effect of different factors on an enzyme catalysed reaction using a graph?
You can plot the amount of product produced against time which should give you a curve. You can then measure the initial rate of reaction (during the first 30 seconds) by drawing a tangent to the curve at the start and measuring the gradient of this line.
Why is it more comparable to measure initial rate of reaction?
Because the initial rate of reaction is when concentrations of enzyme and substrate are known (and have not yet become limiting) so the rates can be compared.
