GCSE Biology Coursework- The effects of a named variable on the action of the enzyme trypsin

SHAMIMA SHALLY 11TI

Background Knowledge: Enzymes are biological catalysts that speed up the rate of reaction without themselves being used up. These reactions do not change the catalyst and so, even small amounts of enzyme can do a big job. Enzymes are composed of polymers of amino acids. Enzymes also are:

Protein- whose chemical shape is special to the substance it works on.
Specific- starch alone fits into the special shape of the enzyme salivary gland, not protein or anything else, so starch alone is digested by it.
Temperature Sensitive- boiling destroys enzymes (by altering their shape); cooling only slows down their action.
PH Sensitive- each enzyme has its own optimum PH e.g. optimum pH for pepsin is pH2 (acid); for salivary amylase pH6.8 (almost neutral); and for lipase pH9 (alkaline).

Collision Theory

Chemical reactions take place by chance. Particles need to collide with enough velocity so that they react. As the temperature is increased the particles move faster since they have more energy. This means that they are colliding more often and more of the collisions have enough velocity to cause a reaction. Since there are more collisions the chemical reaction takes place faster.

There are four main factors that can alter the rate of reaction of trypsin in the clearing of photographic film. Photographic film has clear acetate at the bottom; a layer of gelatine (a substrate) that is in the middle and a silver compound (which is now black) is on top. When trypsin is added, the gelatine breaks down, which leaves the clear acetate exposed. The rate at which this happens is dependent on four factors: temperature, pH, concentration and inhibitors.

Temperature

Generally, enzymes work best around the temperature 40°C. If the temperature is lower than this optimum temperature than the molecules will move slower and therefore there will be a smaller amount of collisions between the enzyme molecules and the substrates. This would result in a slower rate of reaction. However, if the temperature were higher than the optimum temperature for the enzymes to work, than the rate of reaction would slow down as some of the enzymes would have denatured. If the temperature were high enough to denature every enzyme molecule than no reaction would take place.

PH

This can alter the rate of reaction of the enzyme trypsin because if the pH is too low or too high for the enzyme, than it will become denatured. This is where the structure of the enzyme would have been changed so that substrates will no longer be able to fit inside the enzyme and therefore will not be digested. The enzyme, trypsin, works best between pH 7 and 8 because it is found in the duodenum, which is slightly alkaline.

Concentration

The concentration of substrate can affect the rate of reaction because if the ...