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  1. Define enzymes:

Proteins that function as biological catalysts.

  1. Investigate and describe the effect of changes of temperature and pH on enzyme activity.

Most enzymes in our body are designed to work at a pH of 7, and a temperature of 37oC, because those are the conditions in most parts of our body, and our enzymes are well adapted to function inside us.

The temperature an enzyme works best at is its ‘optimum temperature’.

The pH it works best at is its ‘optimum pH’.

One exception is pepsin. This enzyme is present in our stomach, and functions best in our stomach’s acidic (HCl) conditions – pH2.

The general rule goes: The lower the temperature (when lower than optimum temperature), the slower the enzyme works; the higher the temperature (after optimum temperature), the less the enzyme works.

The lower the pH (when lower than optimum), the less the enzyme function; the higher the pH (when higher than optimum), the less the enzyme works.

 

  1. Explain the effect of changes in temperature and pH on enzyme activity.

As shown in the graph above, as the temperature rises, the enzyme activity slowly increases until about 37oC. This is because, as the temperature rises, the enzymes and the reactants gain more energy, so the enzyme can break down or put together substance faster.

After 37oC, enzyme activity rapidly falls. This is because some of the bonds forming the enzymes gain too much energy and are broken, so the active site of the enzyme loses its shape, and can no longer function. The enzyme is denatured.

It is much the same for pH. The further away the pH of the environment is from the enzyme’s optimum pH, the more enzymes slow down and denature, thus causing a decrease in enzyme activity.

 

Notes Submitted by Sarah.

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