Enzymes Overview Quiz

Enzymes

• Biological catalysts that speed up chemical reactions by a factor of 10^6 to 10^12 times
• Most are proteins
• Named after the substrate they act on, ending in '-ase' (e.g., amylase, protease), or '-in' (e.g., pepsin, papain)

Characteristics of Enzymes

• Not consumed in the reaction
• Highly specific, interacting with specific substrates
• Recognize, bind, and modify substrates
• Large molecules composed of amino acid chains linked by peptide bonds
• Can be denatured and precipitated by specific reagents (salts, solvents, etc.)
• May require cofactors (non-protein molecules) for their activity

Classes of Enzymes

• Oxidoreductases: Transfer electrons (hydride ions or H atoms)
• Transferases: Move functional groups between molecules
• Hydrolases: Break down molecules by adding water
• Lyases: Add groups to double bonds, or form double bonds by removing groups
• Isomerases: Rearrange atoms within a molecule to create isomers
• Ligases: Join two molecules together, often using energy from ATP

How Enzymes Work

• Enzymes have specific 3D shapes that fit their substrates
• The active site on the enzyme binds the substrate
• Forms an enzyme-substrate complex, lowering activation energy
• After the reaction, the product is released and the enzyme can bind another substrate

Models of Enzyme Action

• Lock-and-Key Model: Substrate's shape precisely fits the enzyme's active site
• Induced Fit Model: Enzyme changes shape slightly to accommodate the substrate for optimal fit

Active/Inactive Forms of Enzymes

• Apoenzyme: Inactive enzyme without its cofactor
• Coenzyme: Non-protein organic molecule loosely bound to the apoenzyme
• Prosthetic Group: Organic molecule tightly bound to the apoenzyme
• Metal Ion Activator: Inorganic ions that assist in enzyme activity (e.g., K+, Fe2+, Ca2+)
• Zymogen or Proenzyme: Inactive precursor of an enzyme, activated by removing a portion of its polypeptide chain

Factors Affecting Enzyme Activity

• Temperature: Increases reaction rate up to an optimum temperature, then denaturation occurs at higher temperatures
• pH: Enzymes have a specific pH range for optimal activity, outside of which they can denature
• Enzyme Concentration: Higher concentration, faster reaction rate
• Substrate Concentration: Increases reaction rate up to saturation point, where all active sites are occupied
• Covalent Modification: Phosphorylation or methylation can alter enzyme activity
• Inhibition: Competitive, non-competitive, or uncompetitive inhibitors affect enzyme activity
• Allosteric Effects: Regulatory molecules bind to an allosteric site, altering enzyme shape and activity

Enzyme Regulation

• Feedback Control: Products of a reaction pathway can inhibit earlier enzymes in the pathway, preventing overproduction
• Proenzyme Activation: Inactive proenzymes are activated when needed (e.g., trypsinogen to trypsin)
• Allosteric Regulation: Binding of regulatory molecules at allosteric sites can either activate or inhibit enzyme activity

Test your knowledge on enzymes, the biological catalysts that accelerate chemical reactions. This quiz covers their characteristics, classes, and the roles they play in biochemical processes. Perfect for students studying biology or biochemistry!