required practical 1: Variables on enzyme controlled reactions

Question 1

What factors is the rate of an enzyme controlled reaction controlled by

Answer 1

. Temperature
. PH
. Concentration of substrate
. Concentration of enzyme
. Concentration of competitive and non competitive inhibitors

Determine the effect of these by changing a single variable and measuring its effect on the rate of reaction

Question 2

What enzyme is used in this reaction

What does it do, what type of enzyme is it

Answer 2

Trypsin

It is a protease so hydrolyses insoluble protein into small, soluble peptides

Question 3

How can you measure enzyme activity of trypsin

Answer 3

Measure the time for a cloudy protein solution to be clear

Question 4

Describe the method of making two control variables before the experiment

Answer 4

. Take two flat bottomed tubes
. Add 5cm^3 of milk suspension to each tube
. Add 5cm^3 of distilled water to one tube as a control variable, indicating the absence of of the enzyme
. Add 5cm^3 of HCl to the other, this control indicates the colour of a completely hydrolysed sample

Question 5

After the controls are made, what is the method to carry out the experiment of temperature affecting enzyme activity

Answer 5

. Take 3 test tubes and measure out 5cm^3 of milk into each.
Place in water bath at 10 degrees for 5 mins to equilibrate

. Take another 3 test tubes with trypsin and put in the water bath so they reach the same temp

. Add 5cm^3 of trypsin to each test tube simultaneously and start the timer immediately.
.Record how long it takes for the milk to completely hydrolyse and become colourless

. Repear these steps at 20 degrees, 30, 40 and 50

Find the mean time for the milk to be hydrolysed at each temperature

Question 6

How do you work out rate of reaction in this reaction

Answer 6

1/ mean time

Question 7

What are the independent, dependent and control variables

Answer 7

Independent:
The temperature of solution

Dependent:
The time taken for reaction to be complete which tells us the rate of enzyme activity of trypsin

Control:
.PH
. Volume of milk / trypsin solution added
. The enzyme used

Question 8

What do you do with the results from this

Answer 8

Put them into a table and then plot them on a line graph

Question 9

Describe the reasoning behind trypsin hydrolysing the milk

Answer 9

. Milk contains the protein caesan
. So when the trypsin hydrolyses it to break it down, the milk turns colourless

Question 10

How does temperature affect the enzyme activity of trypsin

Answer 10

. As temp increases from 10 degrees, kinetic energy increases so more enzyme-substrate complexes form.
This increases rate of reaction up until the optimum temperature

. After the optimum, bonds in tertiary structure of active site break so the active site changes shape so it is no longer complimentary to the substrate

So fewer enzyme substrate complexes form