Biology Coursework


-We shall investigate the effects when changing the temperature on the rate of a Protease Enzyme called Trypsin on gelatine.

-We will be using photographic tape which has a layer of gelatine and we will try to get this layer off so we have a layer of clear plastic left only.


The four factors, which will affect the rate of reactions, are-


-Surface area


-Process of a catalyst


Temperature will alter the rate of reaction. This happens because if the temperature goes to low then the molecules will slow down and there for there will be fewer collisions of enzymes and the rate of reaction will be slower. However, if the temperature is too high the enzymes will become denatured and they will slow down. If you slow down the rate of reaction or the temperature is too high then no reaction will take place.

Surface Area

When the surface area of the photographic film is large the reaction will be slower this is because if the size of the film is big then there will have to be more particles for the enzymes (trypsin) to collide with the gelatine. However, if the surface area is small there will have to be fewer collisions for the reaction to take place. The surface area affects the rate of reaction because when there is an equal amount of the substance; the substance with the larger surface area will react more, meaning that there is more surface area exposed for the acid to attack.

Concentration of solution

The concentration of the solution affects the rate of the reaction. If the concentration is too high, there will be more collisions between the enzymes, which will also make the rate of reaction faster. On the other hand, if the concentration is to low then the collisions of enzymes with substrates will slow down or stop making the rate of reaction slower. This means that there will be less frequent collisions between the atoms. When there are more particles present, the more likely a collision, and so the higher the reaction rate.

Process of the Catalyst

A catalyst is a substance, which increases the rate of reaction. In our experiment we will use Trypsin as a biological catalyst. However, the catalyst itself is not changed or modified in any way during the experiment. The particles in the enzyme speed up because the catalyst acts as a platform for which the particles can collide. This increases the rate of reaction because it means there are more collisions. This would not happen and there would be fewer collisions if there were no catalysts present in the reaction.


I predict that the higher the temperature the faster the enzymes will work meaning that the Gelatine will be digested faster. Most enzymes work well at 37 C. This is why I predict that the gelatine will be digested at its maximum rate at 40 C. I think this because the higher the temperature is the faster the particles will collide. However, I did not choose 50 C or 60 C because I think that at this high temperature the enzyme may become denatured.


My main reason for my prediction was based on the collision theory and the body temperature. The collision theory is based on the knowledge that chemical reactions take place by chance. However, in order to react the particles must have enough energy to overcome the activation energy. In this experiment between Trypsin and Gelatine, the rate of reaction will be affected by the concentration, surface area, catalyst and temperature. The concentration of trypsin in this investigation will remain constant; however, the temperatures will be ever changing. I also made this prediction because Trypsin is used as an enzyme in the body, and as the body temperature is 37 C the optimum temperature for this enzyme should be roughly 40 C.

When the temperature starts to increase, the trypsin molecules gain more kinetic energy and therefore will collide more with the gelatine molecules. This is the kinetic theory, which states that if the particles are given heat there will be more kinetic energy. This in turn will mean the enzyme will have more energy and that the enzyme will have more collisions.

I made this prediction based on what I have leant and what I know about