Biology Enzyme Experiement

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An enzyme is a biological catalyst. It speeds up a reaction by lowering the activation energy required to start the reaction. It speeds up a reaction, but remains unchanged unless certain limiting factors are introduced. It is composed of polymers of amino acids. An enzyme has an optimum pH and temperature. When an enzyme is at its optimum conditions, the rate of reaction is the fastest. 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. An enzyme has an active site, which has a unique shape into which only a substrate of the exact same unique shape can fit. When this substrate fits into the active site, it forms an enzyme-substrate complex. This means that an enzyme is specific. Renin is a protein (enzyme) released by special kidney cells when you have decreased salt (sodium levels) or low blood volume. Renin also plays a role in the release of aldosterone, a hormone that helps control the body's salt and water balance. Rennin causes rapid clotting of milk by causing certain bonds to break in the soluble casein molecule (milk protein) converting it to the insoluble casein, thus producing “curdled” milk.

There will be 3 different types of experiments which all have consisted of using the main ingredient, renin. The 3 factors I will be experimenting on which affect the activity of the enzyme (renin) are temperature, pH levels and substrate concentration.

The aim of this of the experiment was to see how long it will take for 20ml milk to curdle at different temperatures when renin is mixed with it.

My hypothesis is that the higher the temperature of the milk the faster the time it takes for the milk to curdle. An increase in temperature results in more kinetic energy of the enzyme and the substrate. More kinetic energy results in more collisions between the enzyme and the substrate. In turn, the number of successful collisions increases and more enzyme-substrate complexes form. Therefore an increase in temperature increases the rate at which enzyme substrate complexes form.

The obvious trend of the graph is that as the temperature of the milk was getting greater and greater, the time it took for the milk to curdle was shorter. So the lower the temperature the longer it took to curdle. The higher the temperature the faster it took for the milk to curdle.

In conclusion my hypothesis was correct, the higher the temperature of the milk the faster the time it takes for the milk to curdle.

Independent variable – the temperature of the milk inside the test tube. Dependant variable – The time it takes for the milk to coagulate (by performing the 90 degrees test) Controlled Variables – The size of the test tube, amount of milk poured into each test tube, amount of renin mixed inside test tube, same weather condition. METHOD

- Make a bucket full of hot water. Dunk a 250ml beaker inside bucket and fill about 200ml. - Get half a tablet of renin and put it inside a small beaker with 5ml water in it. Smash up the renin while inside the beaker and let it dissolve. - Pour 20ml of milk into a test tube and place it into the beaker with hot water. - place a thermometer inside the test tube and when the thermometer shows your needed temperature of the milk. - When the temperature is reached quickly pour the dissolved renin into the milk and time how long it takes for the milk to curdle. - To check if the milk has curdled, do 90 degrees tilt test.(turn the test tube 90 degrees and if the milk doesn’t drip out then the milk has curdled. - record both time taken and the temperature at which you had poured the renin into the test tube. - Do the exact same thing but vary the temperature of the water so there is a range. - Repeat experiment and take averages for accuracy.

TEMPERATURE – 20ml of milk poured...
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