Temperature and the Enzyme Rennin
Enzymes are chemical reactions that speed up the process in our cells.
They can also be known as biological catalysts. They are useful
because the enzyme can be used again and again. The enzyme does not
form a chemical bond with the substrate therefore once the products of
the reaction are released, the enzyme
returns to its normal shape.
Only a small amount of the enzyme is needed to control the reaction
and only 1 type of enzyme can be used on a particular substrate. They
influence the rate of the reaction by speeding up the chemical
reactions. E.g. digestion.
Enzymes can be affected by temperature and pH. Temperature increases
the rate of the activity up to the enzymes optimum temperature
However as the temperature rises the enzyme denatures and is no longer
useful. The enzyme no longer fits the active site. The optimum
temperature for each enzyme changes. For instance, for mammalian and
microbial enzymes their optimum temperature is often between 30-45C.
However this is different in plants as their optimum temperature is
Diagrams show that only 1 type of enzyme can fit into an active site.
Also shows enzyme has denatured and no longer fits the active site.
Graph shows how the level of activity rises and falls with the
increase of temperature.
The effect of pH on the enzyme also varies greatly. Very few pH
optima’s are below 3.0 or above 9.0. Many hydrolase’s have an optimum
of around 4.5-6.0.
Graph shows how the level of activity rises and falls with the change
to the pH.
Here we can see that optimum pH level is around 5.
The table below shows what the optimum pH level is for each enzyme.
4.0 - 5.0
Lipase (castor oil)
1.5 - 1.6
7.8 - 8.7
6.1 - 6.8
6.7 - 7.0
4.6 - 5.2
The kinetic collision theory is particles that collide because of the
energy given when heated. The molecules move faster therefore having a
greater chance of colliding with one another. The particles must have
enough energy before the reaction takes place known as activation
energy to break a bond to initiate a reaction.
The enzyme rennin
is a biological catalyst and is found in the stomach
of a young mammal. It is one of two enzymes that is found in the
stomach, the other one being pepsin which replaces the important
enzyme after a period of time as it is no longer needed as much.
Rennin causes the milk to solidify to slow down the digestion of the
milk allowing the young mammal to gain the nutrients it needs. This is
known as coagulation. The casein in the rennin substrate is what
coagulates the milk.
[IMAGE][IMAGE]Casein + Rennin
I am going to investigate the effect that temperature has on the
enzyme rennin. The variable I will change will be the temperature. The
temperature will be changed from 10C-60C to see how the enzyme is
affected. The variable I will measure will be the volume of filtrate.
This will change depending on how the enzyme is affected and how much
it coagulates. The more it coagulates the less filtrate there will be.
The variables I will control are:
* Reaction time (1 minute)
* Filtration time (2 minute)
* Volume of acid (5ml)
* Volume of milk (15ml)
* Volume of rennin (1ml)
* Some number of filter papers (1)
* Same syringe for each substance
* Same type of milk used (semi-skimmed)
* The enzyme from the same bottle
* Same concentration of acid
* Same concentration of milk
* Same concentration of rennin
I predict that the optimum temperature is going to be around 37C as
this is the body temperature of mammals. This would make sense since
the enzyme rennin is found in the stomach of young mammals. I predict
this because enzymes prefer higher temperatures therefore it being
‘happy’ in the stomach. I also predict that rennin would prefer acidic
conditions since it is found in the stomach. Adding to this I believe
that as the temperature becomes closer to 37C that there will be less
filtrate. As well as this, I think that there will be more at 10C and
60C as at 10C the milk wont be coagulating and at 60C the enzyme has
Milk (15ml for each test)
Large beaker (used for water for cooling)
Small beaker (used for filtrate)
Rennin (1ml for each test tube)
Water bath (used for heating at a certain temperature)
Syringes (one each for different substances)
Boiling tube stands (to hold test tubes)
Kettle (used for higher temperatures)
Ice (used for cooling substances)
* First we will fill the test tubes up with 15ml of milk.
* Then we will use separate test tubes to add 5 ml of hydrochloric
acid and in the same test tube as the acid, 1 ml of rennin.
* Then we will add the acid and rennin to the milk. Another person
will start the stop clock.
* We will not stir and shake the test tube, as this could make it an
* As soon as the stop clock reaches 1 min we will filter the
* We will leave the stop clock running so not to make it an unfair
* After this, we will take the mixture and whole funnel with filter
paper in out of the small beaker at the end of the 2 mins of
* Now we will measure the filtrate using a syringe.
* There should be more filtrate when the temperature is low or above
optimum temperature and hardly any around 30-45C.
* We will repeat this for different temperatures to see how the
activity of the enzyme is affected.
* We will then record our results in a table to compare them.
Volume of filtrate (ml)
Volume of filtrate (ml)
Volume of filtrate (ml)
Average volume of filtrate (ml)
Average filtrate rate (ml/s)
From the results I can see that this does match my prediction and the
optimum temperature seems to be around 30-40C. The average volume of
filtrate is at the 60C but I believe this to be wrong, as one of the
results was 13.8, which dramatically changes the results. This result
should be around 4 because of the other results.
Overall I believe that more test could have been done so more results
could have been given. I also think that more temperatures could have
been done especially around the 30-40C mark, as this was what I
predicted. Using intervals of 5C would have been better had it not
have been for the limited time.