Mr Exham's Guide to writing up a Biology Practical Investigation
Making Sense of Biology
10 Sections of a good write-up
2. Background Information
7. Risk Assessment
9. Analysis and conclusion
10. Evaluation and extensions
• I have expanded on each section on the
• I have used an experiment on enzymes to give
you a brief starting point and example for
• This should be a clear descriptive title
outlining the investigation.
An experiment to investigate the effect of temperature on the
rate of breakdown of starch by the enzyme amylase.
2. Background information
• This is where you go over all the biology that you can find on this
topic in order to form an educated hypothesis rather than just a
• Don’t forget to reference info from sources by putting in a
bibliography at the end of the write up.
In this case the following questions should be addressed.
What is an enzyme? How do enzymes work? Where do you find
amylase naturally? How do enzymes usually behave at different
temperatures and why?
• Now that you have explained all the biology
you should be able to make a clear statement
as to what you expect to happen.
As the temperature increases so does the rate of reaction. However
at a certain temperature the enzyme will become denatured and the
rate will rapidly decrease.
• Identify each of the variables in the experiment,
what type they are, and how they are controlled
or measured. This is done best in a table.
Variable Type How measured/controlled
Temperature Independent Thermometer and water bath
Rate of reaction Dependent Time using stop clock
Concentration of amylase Control Prepared at 1%
Concentration of starch Control Prepared at 5%
Volume of amylase Control 2ml using syringe
Volume of starch Control 10ml using syringe
Etc. Etc. Etc.
• This should be a detailed list of what apparatus is required
to carry out the experiment with a justification as to why it
is being used.
• Make sure you use sizes and qty.
• Again this is easy to represent in a table.
Apparatus QTY Justification
Boiling tubes X10 To put the starch in
2ml syringe X1 For transferring the amylase
Thermometer x1 For measuring the temperature
500ml Beaker x1 To make the water bath
Stop clock X1 To measure time taken to break down starch
Iodine solution 100ml X1 To test for starch
Etc. Etc. etc.
• This must be a step by step numbered guide as to how to
carry out the experiment.
• You can include a diagram of the set up if it is required.
• Someone should be able to recreate exactly the experiment
you carried out using this method.
1. Using the 2ml syringe transfer 2ml of amylase into a boiling tube.
2. Using the 10ml syringe transfer 10ml of starch into another
separate boiling tube.
3. Fill the 500ml beaker with 200ml of tap water.
4. Prepare a water bath using a Bunsen burner, heat proof mat,
tripod and gauze and heat to 80oC
5. Place the two boiling tubes in the water bath.
7. Risk assessment
• This should identify any risks in your method.
• Think about heating, glass wear, chemicals, harmful
• Once again a table can be an easy way to show this .
Risk Precaution taken
Bunsen Burner Tie hair back, wear goggles, stand up
• First you must have a table of results. It should
– A descriptive title.
– Clear column headings.
– Units in headings only.
– All data to the same number of decimal points.
– Independent variable as first column.
– Make sure you have at least 5 repeats to work out
a mean and a standard deviation.
A table of results to show the time taken for amylase to breakdown starch at various temperatures
For example . . .
• Sometimes you have raw data that needs further processing. In this
case show your final table in the results section and the original raw
data in an appendix at the back of your write up.
• In this example we need to process the time data to get a rate by
• Therefore this table would go in the results and the first table in the
raw data in the appendix.
A table to show how temperature effects the rate of breakdown of starch by the enzyme amylase
• The next stage is to draw a graph of your
results. It should have:
– A descriptive title
– Labelled axis with units in brackets
– Suitable scale
– Use as much of the paper as you can.
– Drawn in pencil (you can use a computer for the
graph but it’s sometimes hard to get it perfect).
– Join points with a ruler, don’t extrapolate past the
first and last point.
• You can also add error bars to show the spread of
your data around each mean.
• Plot one standard deviation up from the mean
point and one down and turn it into a bar like the
9. Analysis and Conclusion
• First analyse the data, what are the trends? And can you
conclude anything from the data.
• Relate this back to your hypothesis, does it agree or
• Also relate back to your background info section in order to
explain the results using science.
The results show that as you increase the temperature the rate of
reaction also increased up until the optimum temperature of 30oC
when it then decreased rapidly. This proves the hypothesis was
The results occurred due to increase in kinetic energy of both the
substrate and the enzyme making more collisions occur and form
more enzyme substrate complexes . . .
• In this section you need to critically evaluate the experiment. What
were the errors in the method that caused a decrease in accuracy?
Why was the standard deviation so large on some temperatures?
Were there any inaccuracies in the apparatus?
• For each issue you must suggest a suitable improvement.
• You should then also discuss how to extend the practical further to
deepen your investigation into the aim.
The water bath was very hard to maintain at the correct temperature
throughout the experiment. This would cause the results to be less accurate
and would account for some of large standard deviations in the data. In
order to improve this I would use a thermostatically controlled electric water
bath. . . .
To extend this experiment I would test more intermediate temperatures
especially between 30 and 40 in order to more closely identify the optimum
temperature . . .