RP 1- Effect of a named variable on the rate of an enzyme-controlled reaction. Flashcards
What are the 5 variables that could affect the rate of an enzyme controlled reaction?
Enzyme concentration, substrate concentration, pH, temperature, competitive and non-competitive inhibitors
What is the independent variable if you are analysing the effect of temperature?
Temperature
What is the dependant variable in each possible reaction?
The rate of reaction
What are the control variables?
Everything that you are not changing. Eg- if you are changing the temperature then you have to keep substrate/ enzyme volume and concentration, pH and any inhibitor concentration the same.
What is the enzyme trypsin?
A digestive enzyme that catalyses the breakdown of the protein casein in milk- as this reaction occurs the colour of the milk changes from white to clear.
What is the enzyme amylase?
A carbohydrase that hydrolyses (breaks down) starch into maltose. A few drops of iodine solution would be blue/black as the starch would be present but then would turn brown as the starch would be broken down.
What is the enzyme catalase?
An enzyme found in the cells of most organisms that breaks hydrogen peroxide down into water and oxygen. Oxygen gas bubbles can form.
What is the enzyme protease?
An enzyme that catalyses the hydrolysis of peptide bonds and converts them to amino acids.
How could you investigate the effect of temperature on an enzyme controlled reaction?
Eg- the effect of temperature on the ROR catalysed by trypsin.
1) Use marker to draw an X on one side of each of 3 test tubes.
2) Add 10cm3 of 3% solution of milk powder to each test tube.
3) Add 2cm3 of 0.5% trypsin solution to 2cm3 of pH 7 buffer to 3 other test tubes.
4) Stand all 6 test tubes in water bath at 20 degrees for 10 min.
5) Add each trypsin and buffer solution to each milk powder solution test tube, place a bung in each test tube and invert 5 times to mix.
6) Place the 3 test tubes back in the water bath.
7)Time how long it takes for the X to become visible/ for the solution to turn clear.
8) Repeat at 30, 40, 50 and 60 degrees C.
How could you investigate the effect of substrate concentration on an enzyme controlled reaction?
Eg- the effect of enzyme concentration on the ROR catalysed by trypsin.
1) Dilute 1% trypsin solution by adding distilled water to produce solutions with
concentrations of 0.2%, 0.4%, 0.6% and 0.8. Eg- 1g of trypsin in 100ml distilled water= 1% trypsin solution.
2)Have to make a control to set the colorimeter absorbance to 0- could add 2cm3 of trypsin solution and 2cm3 distilled water.
3)To a cuvette, add 2cm3 of milk suspension and 2cm3 of the stock trypsin solution. Mix, place in colorimeter and measure absorbance at 15 second intervals for 5 minutes.
4) Rinse the cuvette with distilled water and repeat the pervious step at all trypsin concentrations.
How do you alter your experiment for enzyme concentration to investigate effect of substrate concentration?
Keep the 1% trypsin solution the same and dilute the milk suspension to create different concentrations of it.
How could you investigate the effect of pH on an enzyme controlled reaction?
1) Add a drop of iodine solution to each well of a spotting tile.
2) Use a water bath at a constant temperature of 35 degrees.
3) Use syringe to add 1cm³ of amylase solution to 1cm³ of pH 5 buffer solution to a boiling tube. Use test tube holders to put the tube in the water bath for 5 minutes.
4) Use a different syringe to add 5cm3 of starch solution to the test tube.
5) Mix and start stopwatch, use pipette to take fresh sample from the boiling tube every 30 seconds and put a drop in a well. When the iodine solution remains the same colour, starch is no longer present.
6) Repeat experiment with different pH buffers.
What you are measuring (dependant variable) goes on the y axis.
