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  • Rights: The University of Waikato Te Whare Wānanga o Waikato
    Published 3 February 2022 Referencing Hub media

    Enzymes are involved in essential biological cellular processes in all living organisms. This animation provides a visual explanation about how enzymes catalyse cellular processes.

    Find out more about enzymes and research looking for the unique enzymes found in extremophilic microorganisms:



    Inside every living cell, thousands of chemical reactions are taking place all the time.

    Many of these chemical reactions wouldn’t occur naturally inside a living cell without the help of a class of biomolecules called enzymes. Enzymes are catalysts – they are proteins designed to allow chemical reactions to happen within living organisms. Life would be impossible without them.

    An enzyme initiates and speeds up a chemical reaction and makes sure the products created are always the same.

    Almost all of our essential cell chemistry and biochemical processes rely on enzymes. Many of these are complex sequences of reactions, with each step being catalysed by a different enzyme.

    Some of these chemical reactions would take many years or need large amounts of heat energy to occur naturally, if at all, but thanks to enzymes, they can occur within cells in milliseconds – millions of times faster than without them.

    In a normal chemical reaction, an unstable threshold called the activation energy, or transition state, needs to be overcome before the substrates can react to form the products.

    Enzymes enhance the reaction rate by forming a stable transition state – acting as a template for the reaction and binding the substrates in the correct position for the reaction to occur. This leads to a more rapid and controlled chemical reaction, which doesn't require as much energy.

    Let’s take a closer look at how enzymes work.

    This is a model of an enzyme showing the active site. An active site often resembles a small cave. This is where the reactions take place.

    The active sites are embedded within the three-dimensional structure of the enzyme. A lot of the enzyme’s molecular structure is about scaffolding its active site.

    The chemical groups on the amino acids at the active site are situated in the exact position to recognise the substrates and then to hold the substrate in position for the reaction to begin.

    The substrates come in, bind to the chemical groups on the amino acid at the active site and the chemical reaction is catalysed. The local chemical environment inside the active site makes the situation very favourable, so the reaction can happen very quickly.

    When the reaction has been completed, the products of that reaction will move away from the active site.

    The scaffolding of the enzyme molecule isn’t just to support and orient the active site – it is often involved in regulating the behaviour of the active site.

    Many enzymes change shape during the reaction, causing a change in or around the active site to enable the perfect environment for the active site to interact with the substrate.

    The enzyme itself is not changed by the reaction and is ready to continue catalysing the chemical reaction again and again as new substrate molecules arrive. It will continue to catalyse reactions until enough of the product has been manufactured, as long as there is enough substrate to utilise.


    Animated footage source, PDB-101. PDB-101 is the educational portal of RCSB Protein Data Bank.

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