Chemical Change: Enzymes

Enzymes are specialised proteins which act as biological catalysts — they speed up chemical reactions occurring in cells.
Each enzyme is shaped to fit only one specific type of molecule (or a group of similar molecules), called its substrate. The part of the enzyme where the substrate fits into is known as the “active site”.
This specificity results from the unique three-dimensional structure of the enzyme molecule.
In the process known as the “lock and key” model, enzymes and substrates match each other in a similar way as a key fits into a lock, which results in an enzyme-substrate complex.
However, some of the newer exploration explains the activity of enzymes by the “induced fit” model. According to this theory, the enzyme changes its form slightly to accommodate the substrate once it makes contact.
The reaction taking place changes the substrate, converting it into one or more different molecules - these are the ‘products’ of the reaction. After the reaction, the enzyme remains unchanged, and can repeat the process with more substrate molecules.
Enzymes are believed to be involved in almost all the processes essential for life, including food digestion, DNA replication and protein synthesis.
The function of enzymes can be influenced by changes in temperature and pH. There is often an optimum temperature and pH at which an enzyme works best.
If the temperature becomes too high, the enzyme can denature, where it loses its specific shape (and hence its function). Similarly, extreme pH conditions can also denature enzymes.
Inhibitors are substances that reduce the activity of enzymes. Some inhibitors bind to the active site (competitive inhibitors), while others bind to a different part of the enzyme causing the active site to deform (non-competitive inhibitors).
Enzymes have significant industrial and medical applications. They are used in the manufacture of food and drink, cleaning products, and pharmaceuticals. They can also be used for diagnosis and treating certain diseases.

Remember, understanding enzymes and how they work is key to understanding a multitude of biological processes. Instances of their functionality extend far beyond this list, so always be looking for where enzymes can play a part in a given topic.