Enzyme Control of Chemical Reactions in Cells

Enzymes are biological catalysts that speed up chemical reactions in cells without being used up or changed in the process.
Each enzyme is specific to one type of reaction due to their complementary shapes with their substrates, thus, allowing them to bind forming an enzyme-substrate complex.
Like a lock and key, the enzyme’s active site matches the shape of its specific substrate. This model explaining enzyme action is called the ‘lock and key’ model.
Enzyme activity can be affected by temperature, pH, and substrate concentration. Each enzyme works best at an optimum temperature and pH.
Temperatures above an enzyme’s optimum level often causes the enzyme to denature. Denaturation alters its shape, preventing it from binding to its substrate.
Similarly, if the pH is too high or low, it can affect the bonds holding the enzyme together, also leading to denaturation.
The rate of reaction increases with substrate concentration up to a point. When all the active sites of enzymes are engaged, the rate of reaction reaches a plateau. It cannot increase any further because the maximum enzyme activity has been reached.
Cells can control metabolic pathways using enzymes by switching on or off the genes coding for these enzymes.
Competitive and Non-Competitive inhibition are two ways by which enzyme activity can be controlled. Competitive inhibitors compete with the substrate for the active site whilst non-competitive inhibitors bind to another part of the enzyme causing it to change shape, inhibiting the enzyme’s function.
Enzymes play a vital role in processes such as respiration, digestion, DNA replication, protein synthesis, and many more.
Understanding enzymes and how they work is crucial in the study of cells and their functions, which is a central theme in biology.
Enzyme research has led to various applications including the development of drug therapies, the food industry, biotechnologies, and environmental applications.

Remember to use diagrams where possible when revising this topic as they can greatly aid in understanding and recalling the information. Get familiar with the definitions and the conditions that affect enzyme activity. Always remember that practise makes perfect - keep using past papers or sample questions to test your knowledge.