Enzyme Structure

Enzyme Structure

Enzyme Basics

  • Enzymes are types of proteins that speed up chemical reactions in cells by lowering the activation energy.
  • The substance that the enzyme acts upon is known as the substrate.
  • They are vital for life and serve a wide range of important functions in the body, such as aiding digestion and metabolism.

Structural Characteristics of Enzymes

  • Enzymes are made up of amino acids which are linked together in a specific order.
  • The sequence of amino acids determines an enzyme’s unique 3-dimensional shape, which is crucial for its function.
  • Each enzyme has an area known as the active site where substrate molecules bind and undergo chemical reactions.

Substrate Binding

  • The unique shape of an enzyme allows only specific substrate molecules to bind with it. This is called the lock-and-key model.
  • Sometimes, enzymes change shape slightly to embrace the substrate. This is known as the induced fit model.
  • The active site and the substrate have complementary shapes, and the interaction between them is what makes the chemical reaction possible.

Enzyme Specificity

  • Enzymes are highly selective catalysts, meaning they only catalyse specific reactions.
  • Each type of enzyme only reacts with a specific type of substrate, due to the unique shape of the active site.

Effects of Environmental Factors on Enzyme Function

  • Factors like temperature, pH, and enzyme concentration can affect enzyme activity.
  • Each enzyme works best at a specific temperature and pH, referred to as the enzyme’s optimum conditions.
  • Beyond those conditions, the enzyme may denature, losing its shape and function.

Enzyme Regulation

  • Cells can turn enzymes on or off using molecules that either enhance or inhibit their function.
  • These regulatory molecules can bind to enzyme’s active site or to another part of the enzyme, changing its shape and preventing it from binding with its substrate, a mechanism known as allosteric regulation.

Coenzymes and Cofactors

  • Some enzymes need non-protein helpers to perform their function, these can be organic (called coenzymes) or inorganic (known as cofactors).
  • Coenzymes and cofactors either bond temporarily or permanently to the enzyme and can be crucial for the enzyme’s function.