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Investigating the Different Concentration of Catalase On the Breakdown of Hydrogen Peroxide.

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INVESTIGATING THE DIFFERENT CONCENTRATION OF CATALASE ON THE BREAKDOWN OF HYDROGEN PEROXIDE General Aim: My central aim is to find out whether the change in concentration of catalase (enzyme) affects the rate of oxygen produced. Scientific Theory on enzymes: Enzymes have an optimum temperature and pH at which they work best, this is the body temp. Enzymes are known as biological catalysts and are globular proteins with a tertiary structure, therefore they are very specific in the reactions that they catalyse. One enzyme will react with molecules of one substrate. The Active site where the reaction occurs is situated on the surface of the enzyme. The Active site for all molecules of one enzyme will be made up of the same arrangement of amino acids. Generally an enzyme molecules consists of one Active site and only one type of substrate have a complementary structure Enzyme reaction: Enzyme + Substrate Enzyme-Substrate complex Products + Enzyme (Transition state) The substrate binds with the enzyme in the Active site to form an enzyme-substrate complex, this temporarily formed. Later it is left with the products and the enzyme. Structure of a enzyme: Enzymes are globular proteins with a tertiary structure therefore consists of a long chain of amino acids linked by peptide bonds forming a polypeptide. These polypeptide chains bend and tightly fold joined by 4 types of bonds called: hydrogen, ionic, disulphide bonds and hydrophobic interactions. This gives the enzyme a complex 3D globular shape called tertiary structure. The globular protein curls up so the non-polar hydrophobic 'R' group points towards the centre of the molecule, so its kept away from the surrounding water. ...read more.


However if we continue to increase the substrate concentration using the same volume of the substrate keeping the variable enzyme concentration and volume used constant there comes a point where this pattern draws to a halt. The rate of reaction will not continue to increase. This is because a higher substrate concentration active site of all the enzyme molecules is saturated with substrates. Extra substrate molecules have to 'line up' to form their products. The number of enzyme molecules becomes a limiting factor. The rate of reaction at higher substrate becomes constant. Enzyme concentration: If the number of enzyme molecules present is raised to react with plenty of substrate molecules in a reaction mixture then the rate of reaction will be faster. This is because more active sites will be available for substrates to bind with and form enzyme-substrate complexes and release products. If there comes a point where there are small amounts of substrates then adding extra molecules gas there will be no effect on the rate of reaction. There are not enough substrates available for the enzymes active site to bind with, this means that at high enzyme concentrations the graph line does not continue to go up but levels off. Enzyme inhibitors: A variety of small molecules that reduce that reduces the rate of enzyme activity are called enzyme inhibitors. There are 2 types of inhibitors- competitive and non-competitive inhibitors. * Competitive inhibition: Enzymes are highly substrate specific. Only substrate molecules of one particular shape complementary to the shape of the active site will fit perfectly into the active centre. ...read more.


for all five concentrations. Step8: for each concentrations repeat 2 more times for accuracy (3 trials run) starting the timer over again for 180 seconds for each test. Step9: Record the results again in another similar table for both experiments. Accuracy: I used a gas syringe as this measures the volume of gas accurately and in order for the readings to be accurate I tried to look at the gas syringe very carefully at the exact time. for each concentration I had three trial runs to calculate averages as the averages takes in account of the overall data. I used a stop timer as I had to take reading every 15 seconds for 3 minutes for each concentration individually. When measuring out volumes of concentrations I used 10ml measuring cylinders as my concentrations added up to 10ml each ml equivalent to 10 percent. I took measurements at eye level at the bottom of the meniscus. This is formed as a result of the attraction of the measuring cylinder and the solution in it. Safety: Before starting an experiment it is essential to take into considerations on the safety precautions. This involves wearing safety goggles for eye protection all throughout the experiment, especially when handling hydrogen peroxide as it's very toxic. Another safety regulation is to wear gloves to protect hands from getting in contact with the chemicals being used. Making sure nothing is spilled as this may lead to problems and may affect the experiment being carried out. After every piece of equipment is used it is important to place it back into the right places and making sure it is clean and has no chemicals on it. Kulsuma Khanum 13B 1 ...read more.

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