Resources | Subject Notes | Biology
Enzymes are biological catalysts, meaning they speed up chemical reactions in living organisms. They are typically proteins, and their activity is highly specific – each enzyme usually catalyzes only one particular reaction.
Enzymes have an active site, which is a region that binds to the substrate (the molecule the enzyme acts upon). This binding forms an enzyme-substrate complex, which facilitates the chemical reaction.
Enzymes have an optimal temperature at which they work most effectively. Increasing the temperature generally increases the rate of reaction up to a point. Beyond the optimal temperature, the enzyme's structure begins to denature, meaning it unfolds. This disrupts the active site, and the enzyme loses its catalytic activity. Denaturation is irreversible.
The optimal temperature for most human enzymes is around 37°C. Enzymes from organisms living in colder environments (e.g., bacteria in soil) often have lower optimal temperatures. Enzymes from organisms living in warmer environments (e.g., thermophilic bacteria) have much higher optimal temperatures.
The relationship between temperature and enzyme activity can be represented by a bell-shaped curve.
pH measures the acidity or alkalinity of a solution. Enzymes are sensitive to pH changes. Each enzyme has an optimal pH at which it functions best. Changes in pH can alter the ionization state of amino acid residues in the enzyme's active site, affecting its shape and ability to bind to the substrate.
Extreme pH values (very acidic or very alkaline) can cause the enzyme to denature, leading to a loss of activity. The optimal pH varies depending on the enzyme and the organism it comes from. For example, pepsin, an enzyme in the stomach, has an optimal pH of around 2 (very acidic), while many enzymes in the blood have an optimal pH of around 7.4 (slightly alkaline).
To investigate the effect of temperature on enzyme activity, you can perform an experiment where you measure the rate of reaction at different temperatures. The rate of reaction can be measured by monitoring the amount of product formed over time. You would need to keep other factors constant, such as the concentration of enzyme and substrate.
To investigate the effect of pH on enzyme activity, you can perform an experiment where you measure the rate of reaction at different pH values. You would need to use buffers to maintain a constant pH. You would also need to keep other factors constant, such as the concentration of enzyme and substrate.
| Temperature (°C) | Rate of Reaction (units/min) |
|---|---|
| 0 | 0 |
| 10 | Low |
| 20 | Medium |
| 30 | High |
| 40 | Very High |
| 50 | Low |
When analyzing data, it's important to plot graphs of rate of reaction versus temperature or pH. The graphs will show the optimal temperature or pH and the range of temperatures or pH values over which the enzyme is active.
Enzymes are used in many industries, including food production (e.g., amylase in bread making), detergent manufacturing (e.g., proteases to remove stains), and the production of biofuels.