B2 Investigating Enzymatic Reactions (page 26) Flashcards
Can you investigate the effect of pH on Enzyme Activity?
Yes
The Enzyme amylase catalyses the breakdown of starch to what?
maltose.
Its easy to detect starch using what?
iodine solution
If starch is present in the enzyme, what colour will the iodine solution change from?
from browny-orange to blue-black if starch is detected.
(this is how you can detect how pH affects amylase activity),
What is the process of investigating how pH affects amylase activity?
1) put a drop of iodine solution into every wallof a spotting tile.
2) Place a Bunsen burner on a heatproof mat, and a tripod and gauze over the Bunsen Burner. Put a beaker of water on top of the tripod and heat the water until it is 35°C (use a theroeter to measure the temperature). Try to keep the temperature of the water constant throughout the experiment.
3) Use a syringe to add 1cm³ of amylase solution and 1cm³ of a buffer solution wit a pH of 5 to a boiling tube. Using test tube holders, put the tube into the beaker of water and wait for five minutes.
4) Next, use a different syringe to add 5cm³ of a starch solution to the boiling tube.
5) Use continuous sampling to record how long it takes for the amylase to break down all of the starch. To do this, use a dropping pipette to take a fresh sample from the boiling tube every 30 seconds and put a drop into a well. When the iodine solution remains browny-orange, starch is no longer present.
6) Repeat the whole experiment with buffer solutions of different pH values to see how pH affects the time taken for the starch to be broken down.
8) Remember to control any variables each time (e.g. concentration and volume of amylase solution) to make it a fair test.
(you could use an electric water bath, instead of a Bunsen Burner and a beaker of water, to control the temperature too)
Please see diagram on page 26 of the items to use in this experiment)
How can you accurately measure the pH of your solutions during an experiment?
by using a pH meter.
It is often useful to calculate the rate of reaction after an experiment, what is meant by term rate?
Rate is a measure of how much something changes over time
For the experiment on page 26 how can you calculate the rate of reaction?
using this formula:
1000 Rate = \_\_\_\_\_\_\_\_\_\_
time
At pH 6, the time taken for amylase to break down all the starch in a solution was 90 seconds. what would the rate of reaction be?
rate of the reaction = 1000 ÷ 90 = 11s -¹ (2 s.f)
The units are in s-¹ since rate is given per unit time.
If an experiment measures how much something changes over time, how do you calculate the rate of reaction?
by dividing the amount that it has changed by the time taken.
The enzyme catalase catalyses the breakdown of hydrogen peroxide into water and oxygen. During an investigation into the activity of catalase, 24 cm³ of oxygen was released in 50 seconds (s). Calculate the rate of the reaction. Write your answer in cm³ s-¹ ?
Amount of product formed = change = 24 cm³
Rate of reaction = change ÷ time = 24 cm ÷ 50 x = 0.48 cm³ ³ s-¹
(cm³ s-¹ is another way of writing cm³/s
An enzyme-controlled reaction was carried out at pH 4. After 2 minutes, 36 cm³ of product had been released. Calculate the rate of reaction in cm³ s (1 mark)
2 minutes = 2 x 60 = 120 seconds.
36 ÷ 120 = 0.3 ³/s (1 mark)
