Enzymes Overview Quiz

Enzymes

• Enzymes are biological catalysts that speed up chemical reactions without being consumed in the process.
• They are typically proteins, but some RNA molecules can also act as enzymes, known as ribozymes.
• Enzymes bind to specific molecules called substrates, facilitating their conversion into products.
• The rate of an enzyme-catalyzed reaction is higher than the rate of the uncatalyzed reaction.

Enzyme Features

• Enzymes are highly specific, typically catalyzing only one or a small number of reactions.
• Enzymes are subject to regulation, allowing cells to control their metabolic processes.
• Enzymes are affected by temperature and pH, having optimal conditions for activity.
• Enzymes do not change the equilibrium constant of a reaction.
• Enzymes are reusable, participating in multiple rounds of catalysis.

Metalloenzymes

• Metalloenzymes are enzymes that require a metal ion for their activity.
• The metal ion acts as a cofactor, assisting in the catalytic process.
• Examples of metalloenzymes include:
  • Cytochrome oxidase: contains copper and iron ions
  • Carbonic anhydrase: contains zinc ions

Apoenzymes and Cofactors

• Apoenzymes are the inactive form of an enzyme that requires a cofactor to become active.
• Cofactors can be inorganic ions (like metal ions) or organic molecules (like vitamins).
• Holoenzyme is the fully active enzyme containing both the apoenzyme and the cofactor.

Substrate

• The reactant in an enzyme-catalyzed reaction is called the substrate.
• The substrate binds to the enzyme's active site, forming an enzyme-substrate complex.

Enzyme Nomenclature

• Many enzymes end with the suffix -ase.
• Examples include:
  • Lactase: breaks down lactose
  • Protease: breaks down proteins

Hydrolases

• Hydrolases are enzymes that catalyze the hydrolysis of a chemical bond, usually by adding water.
• They break down larger molecules into smaller ones.
• Examples include:
  • Lipase: breaks down lipids
  • Amylase: breaks down carbohydrates

Transferases

• Transferases catalyze the transfer of a functional group (like a phosphate group) from one molecule to another.
• Examples include:
  • Kinases: transfer a phosphate group
  • Glycosyltransferases: transfer a sugar molecule
  • Methyltransferases: transfer a methyl group
• Dehydrogenases are a subclass of transferases that transfer hydrogen ions and electrons.

Subclasses of Transferases

• Phosphotransferases: transfer phosphate groups

• Glycosyltransferases: transfer sugar molecules

• Methyltransferases: transfer methyl groups

• Dehydrogenases: transfer electrons and hydrogen ions

• Acyltransferases: transfer acyl groups

• Isomerases are NOT a subclass of transferases. They catalyze the rearrangement of atoms within a molecule, converting one isomer to another.