Slide 1
Enzymes are biological catalysts
An enzyme accelerates a chemical reaction in a living system. Most enzymes are proteins, although some ribonucleic acid molecules also catalyse reactions.
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The enzyme is regenerated during its catalytic cycle, allowing repeated use. Its presence changes reaction speed, while the equilibrium balance still depends on the reaction’s thermodynamics and conditions.
Slide 2
An active site positions molecules for reaction
The active site is the region where reactants bind and the reaction is promoted. Its shape and chemical groups help position the relevant molecules.
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Recognition involves more than fitting an outline. Charge, hydrogen bonding and other interactions orient the substrate and stabilize arrangements along the reaction pathway, making chemical compatibility as important as geometry.
Slide 3
Binding can change an enzyme’s shape
Enzymes are flexible molecules. Binding a substrate, the substance they act on, can change their shape and improve the arrangement needed for catalysis.
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The simple lock-and-key picture is therefore incomplete. Enzymes sample different structures, and substrate binding can favour some of them; motion is part of function rather than merely a defect in a rigid machine.
Slide 4
Temperature and pH alter activity and structure
Temperature and pH affect enzyme performance. They can change reaction rates, chemical charges and the structure required for catalysis.
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An enzyme’s apparent optimum depends on the measurement conditions and exposure time. A brief assay at a high temperature may differ from prolonged operation if structural damage gradually accumulates.
Slide 5
Cells regulate enzymes as their needs change
Cells control enzymes through abundance, binding partners and chemical modification. Catalysis can therefore respond to the cell’s changing needs.
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An inhibitor can bind at the active site or elsewhere and alter function. Regulation at another site is called allosteric when binding changes activity through the protein’s structure, connecting distant parts of the molecule.
Sources
- Enzyme
National Human Genome Research Institute
- The Central Role of Enzymes as Biological Catalysts
NCBI Bookshelf