Summary
Biological catalysts, mostly proteins, that speed up reactions by lowering the activation energy.
In depth
Enzymes speed reactions by up to a million-fold or more, are specific to their substrates, and are unchanged at the end of the reaction. They lower activation energy by orienting substrates, straining bonds or providing a favourable micro-environment, but do not change the equilibrium.
Names often end in -ase, and enzymes are classified by reaction type (oxidoreductases, transferases, hydrolases and so on). Metabolic pathways are controlled by regulating enzymes.
Most enzymes are proteins, ending in -ase, and are classified by reaction type: oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases. Reaction rates are often expressed by turnover number; catalase can process millions of hydrogen peroxide molecules per second per molecule.
Enzymes are used in industry and medicine: amylases in brewing and detergents, proteases in cheese making, lactase to make lactose-free milk, and DNA polymerase in PCR. Clinical tests measure enzymes such as troponin and creatine kinase to detect heart damage.
Common mistake: saying enzymes are used up or that they supply energy. They are catalysts that only change the rate, not the equilibrium.
Frequently asked questions
What is Enzymes?
Biological catalysts, mostly proteins, that speed up reactions by lowering the activation energy.
Which area of biology covers Enzymes, and how advanced is it?
Enzymes is one of the 51 topics in Biomolecules & Biochemistry. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Activation Energy, Factors Affecting Enzymes, Carbohydrates.
Can you give an example of Enzymes?
Catalase breaks down toxic hydrogen peroxide extremely fast, millions of molecules per second.
What should I learn before Enzymes?
Enzymes is a Beginner topic, so no earlier topic is required. Other Beginner topics in Biomolecules & Biochemistry that pair well with it include Water Properties, Carbon Chemistry, Carbohydrates.
What topics are related to Enzymes?
The closest topics to Enzymes are Activation Energy, Factors Affecting Enzymes, Carbohydrates, Denaturation. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Enzymes?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Enzymes. To practise the whole of Biomolecules & Biochemistry, use the Biomolecules & Biochemistry quiz.
How is Enzymes different from Activation Energy?
Enzymes: Biological catalysts, mostly proteins, that speed up reactions by lowering the activation energy. Activation Energy: The minimum energy needed to start a reaction, lowered by enzymes without changing the overall energy change. Read both side by side and note what each one explains.
What is a common mistake about Enzymes?
Saying enzymes are used up or that they supply energy. They are catalysts that only change the rate, not the equilibrium.
How should I study Enzymes step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Activation Energy and explain the difference aloud. Finally, take the Biomolecules & Biochemistry quiz and come back to this page for any question you miss.