What affects the rate of an enzyme reaction?

Fig.1 Biological Catalyst at work

In their globular structure, one or more polypeptide chains twist and fold, bringing together a small number of amino acids to form the active site, or the location on the enzyme where the substrate binds and the reaction takes place. Enzyme and substrate fail to join together if their shapes do not match exactly. This ensures that the enzyme does not participate in the wrong reaction. The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with a new substrate. Enzymes work to change the rate of a reaction without being absorbed by the reaction. The reactant that an enzyme acts on is called the enzyme's substrate. Enzymes or catalase are used for removing Hydrogen Peroxide from the cells. Hydrogen Peroxide is the poisonous by-product of metabolism. Catalase speeds up the decomposition of Hydrogen Peroxide (which is the substrate) into water and oxygen.

The main variables that affect the rate of an enzyme reaction are as follows:

. Concentration of Enzyme/Hydrogen Peroxide can affect the rate of reaction since this takes us back to the collision theory. If you increase the concentration of the enzyme/Hydrogen Peroxide this will increase the number of particles present and therefore increases the chance of any collisions. So subsequently it increases the rate of the reaction.

2. Temperature conditions of reactants can also affect the rate of reaction for the reason that increasing the temperature of any reactant provides then particles with more kinetic energy thus they will move faster which will then increase the number of collisions per second and for this reason it increases the rate of reaction. Alternatively if you decrease the temperature the enzymes will cease to work beneath or above optimum temperature.

Catalase is an enzyme found both in humans and plants. In humans Hydrogen Peroxide is poisonous and builds up during respiration. To decompose this substance quickly the catalase in our liver acts as an biological catalyst to speed up the reaction. Catalase is the fastest ever enzyme in the human body working at nearly 6x105 reaction per minute. In plants Hydrogen Peroxide builds up also during respiration. In this experiment we are going to use potatoes instead of liver because it can be handled more easily.

The apparatus that I will be using for this experiment are as follows:

* Boiling tubes

* Clamp and stand

* Hydrogen Peroxide

* Knife

* Measuring Cylinder

* Pipette and pen for liquid method

* Potatoes

* Ruler

* Stop clock

* Washing up liquid

My method is as follows:

. First gather all the equipment need for the experiment. Then cut the potato as accurately as you can, using the ruler.

2. Next set up the equipment and measure out the hydrogen peroxide and pour into the boiling tube.

3. After that I will put the washing up liquid using the pipette and then will immediately add the potato. As I drop the potato instantaneously I will start the stop watch and time for 1 minute.

4. I will record the result on a table and do steps 1 to 4 for the rest of the potato sizes.

5. I will then repeat the steps 1 to 4 three times on order to ensure me that the experiment is not just luck.

The variable that will be changed is the size of the potato and the range of the sizes will be five. They are 1x1x1, 2x1x1, 3x1x1, 4x1x1, and 5x1x1 (all in centimetres) I am going to repeat the experiment three times as well because this ensures me that the experiment is accurate and not just by chance.. The other variables that will be controlled are the temperature which will be kept st the room temperature the same person starting and stooping the stop watch. If all these are kept the same then hopefully the experiment will not be biased and will be a fair one.

I predict using the above science as my evidence and research that the larger the size of the potato the more bubbles will be formed. This is because the large potato will have more concentration of catalase and therefore this increases the chance of more collisions and hence increases the rate of reaction and produces more bubbles.

ANALYSING

TIME

x1x1 (cm3)

2x1x1 (cm3)

3x1x1 (cm3)

4x1x1 (cm3)

5x1x1 (cm3)

st

0.8

.2

.1

2.0

2.4

2nd

0.7

.0

.3

.8

.9

3rd

0.7

.1

.2

.6

2.2

AVERAGE

0.7

.0

.2

.8

2.15

I was trying to find out what affects the rate of an enzyme reaction. During the experiment I decided to vary the amount of hydrogen peroxide. From the result table above using the results I have drawn a graph that shows the result above but in a simpler way. As you can see, from the graph that my prediction was absolutely right. I had predicted that the larger the size of the potato the more bubbles that it will form. This is exactly what the graph is telling us. If you look at the potato size 5cm it has produced a lot of bubbles compared to the potato sizes 1cm.

From observing the graph I can clearly draw a conclusion that the higher the concentration of the catalase them faster the rate of reaction and therefore I can also say that the concentration of the catalase can affect the rate of an enzyme reaction. With some brief scientific knowledge I can clearly explain what has happened referring to the graph and the results table. As the concentration of the catalase was higher (the larger the potato size) the rate of the reaction was faster. We can tell this by the amount of bubbles produced. Every reaction has a by-product and if the reaction went at a faster speed there will be more by-products and this is what we can see from the graph. Increasing the concentration of the catalase can affect the rate of reaction. If you increase the concentration of the enzyme this immediately will amplify the number of particles present and as a result boosts the chance of any collisions.

EVALUATION

In doing the experiment I have come across some problems. The most difficult problem was the measuring of the bubbles. As you can see from the results table the amount of bubbles went into decimals i.e. 2.1 cm3 and therefore it was very crucial that the measurement was read carefully and precisely. The problem above can not affect the results in the big picture. I might have been one tenth of a centimetre more or less but this can minimally affect the graph but the idea will still be the same.

Surprisingly there were no odd results. Maybe this was due to the accuracy of my work or maybe it was just luck. The graph has also a line of best fit in which we can see how accurate our results were. The line of best fit goes through three of the points, as this tells us that the results were pretty precise. The other two points are not very far from the line of best fit. This also backs up that the results are pretty precise and accurate.

BIOLOGY COURSEWORK

M.R 11.1