investigating the effect of enzyme concentration on the initial rate of an enzyme-catalysed reaction

hypothesis

the higher the concentration of enzyme, the faster the initial rate of the enzyme-catalysed reaction. the is due to the increased probability of a collision between the enzyme and the substrate molecules

outline of the method

various concentrations of trypsin solutions are used to break down the casein in milk powder. as its digested the cloudy solution begins to clear the rate of which is meased via the colorimeter. the change in transmittance is monitored over a set period and then the data is used to plot graphs to calculate initial rates.

equipment

• 1% trypsin solution

• 10 cm3 volumetric flask

• 10cm3 graduated pipette

• distilled water

• colorimeter

• corvette

• casein solution

• 2cm3 graduated pipette x2

• stopwatch

health and safety

all of the enzymes have the potential to be allergens - any spillages should be cleaned up immediately - washed

structure and function of an enzyme

An enzyme is a biological catalyst. It is a protein molecule which speeds up biological reactions, allowing us to stay alive. Enzymes work by lowering the activation energy of the biochemical processes occurring within our cells.

The structure of an enzyme is vital for its function. An enzyme is made up of amino acid chains folded together in a specific manner resulting in a small area known as an active site, which is where the catalysis occurs.

method

• will be provided with 1% solution of trypsin. decide what concentration of enzyme will be investigated.

• transfer 2cm3 of the casein solution into a cuvette and record the initial transmittance of the solution using the colorimeter

• add 2cm3 of the trypsin solution and stir

• measure the transmittance of the solution at regular intervals for 5 minutes

• use distilled water to rinse out the cuvette

• repeat steps with the 4 other enzyme concentrations

data analysis

plot a graph - and use it to calculate the initial rate of reaction - tangent

evaluation

factors that could lead to decreased validity:

• fluctuations in temperatures

• lack of proof that enzyme cased the change in colour

evaluation - temp

occur due to changes within the environment. therefore the reaction could be carried out using a water bath to maintain constant temp

evaluation - enzyme

a control could be carried out using distilled water in place of the 2 cm3 of trypsin solution

who does the change in concentration of trypsin affect the initial rate of casein breakdown

• as the concentration of trypsin increases, the initial rate of reaction increases

• a comment on the proportionality of the relationship

• a comment referencing an plateauing of results

how would caring out this experiment at a lower temperature would affect the initial rate of trypsin activity

• initial rate would be lower

• fewer enzyme-substate complexes formed

• less kinetic energy

how would carrying out the experiment at increasingly higher tempretures would effect the initial rate of trypsin activity

• temp increase = initial rate increases

• more enzyme substrate complexes formed

• more kinetic energy

• optimum temp

• rate decreases due to denaturing of enzymes

ways of extending investigation

• carry out more re peats for the concentrations investigated, to allow to spot anomalies and increase reliability

• use intermediate concentrations of trypsin around the suggested opium value on the graph, to more accuracy determine the levelling off point

• extend the concentration of trypsin beyond 1%, to extend the range of results