IGCSE Biology Enzymes

Summary:

Enzymes are biological catalysts that speed up chemical reactions in cells. They are necessary because metabolic reactions at normal body temperature would be too slow. Enzymes have specific active sites that fit particular substrates, following the lock and key model. Digestive enzymes are classified into carbohydrases, proteases, and lipases, each breaking down specific molecules. Enzyme activity has optimum conditions, such as body temperature and neutral pH in humans.

One example is catalase, which breaks down hydrogen peroxide into water and oxygen, preventing toxicity. An investigation of the effect of pH on catalase activity involves using potato extract mixed with buffer solutions and hydrogen peroxide to count the number of bubbles produced in a minute. Another investigation on amylase activity examines the effect of temperature using different temperature conditions and measuring its impact on starch breakdown.

In summary, enzymes are vital for cellular reactions, and their activity is influenced by temperature and pH. Digestive enzymes play specific roles in breaking down different nutrients, and catalase is crucial for detoxifying hydrogen peroxide. Experimental investigations can be conducted to explore enzyme behaviour under varying conditions.

Excerpt:

IGCSE Biology Enzymes

Enzymes: Chemical reactions in a cell are called metabolic reactions. The sum of these is known as the metabolism of the cell. Enzymes catalyse these. Enzymes are biological catalysts. A catalyst is a chemical that speeds up the reaction rate, without being used up itself. Enzymes are proteins, and there are many different enzymes. Enzymes are needed because, at normal body temperature (37oC), chemical reactions needed to live would occur too slowly. For a chemical reaction, particles must collide with sufficient energy. At low temperatures, particles have little kinetic energy, so they do not collide frequently enough.

The molecule an enzyme acts on is called the substrate. On the surface of an enzyme, there is an area called the active site. Each enzyme has a differently shaped active site, specific to a particular substrate. This is called the lock and key model.