enzymes

• What are enzymes primarily known as?

  Catalysts for biochemical reactions
• How do enzymes affect the activation energy of a reaction?

  They lower the activation energy of a reaction
• Are enzymes consumed during the reactions they catalyze?

  No, they are not consumed during the reaction
• What is the typical structure of enzymes?

  Usually globular proteins; few are nucleic acids
• What is a catalyst?

  A substance that enables a chemical reaction to proceed at a faster rate
• What is a substrate in the context of enzymes?

  The substance on which an enzyme acts
• What is a product in enzymatic reactions?

  The substance produced by the action of an enzyme on a substrate
• What is the active site of an enzyme?

  The region or domain where the substrate binds
• What is a cofactor?

  A nonprotein component that assists in catalysis
• What is the difference between a simple enzyme and a conjugated enzyme?

  A simple enzyme is composed entirely of protein, while a conjugated enzyme includes a non-protein part
• What is a holoenzyme?

  A biochemically active conjugated enzyme composed of an apoenzyme and a cofactor
• What do cofactors provide to enzymes?

  Additional chemically reactive functional groups
• What are coenzymes?

  Small organic molecules that act as cofactors
• Which metal ions can act as cofactors?

  Zn²⁺, Mg²⁺, Fe²⁺, Fe³⁺, Cu⁺, Cu²⁺
• What is the enzyme nomenclature based on?

  • Suffix –ase indicates that the substance is an enzyme
  • Prefix indicates the type of reaction
  • Identity of the substrate is often noted
• What is the active site of an enzyme characterized by?

  A small portion that participates in the interaction with a substrate
• What is the enzyme-substrate complex?

  An intermediate reaction species formed when the substrate binds to the active site
• What are the two models of enzyme action?

  • Lock & Key Model: Active site has a fixed shape for specific substrates
  • Induced Fit Model: Active site changes shape to accommodate the substrate
• What is enzyme specificity?

  The extent to which an enzyme’s activity is restricted to specific substrates
• What are the types of enzyme specificity?

  1. Absolute specificity
  2. Group specificity
  3. Linkage specificity
  4. Stereochemical specificity
• What does an oxidoreductase enzyme do?

  Catalyzes an oxidation-reduction (redox) reaction
• What is the function of a transferase enzyme?

  It catalyzes the transfer of a functional group from one molecule to another
• What does a hydrolase enzyme do?

  Catalyzes a hydrolysis reaction
• What is the role of a lyase enzyme?

  Catalyzes the addition or removal of a group to form a double bond without hydrolysis or oxidation
• What does an isomerase enzyme do?

  Catalyzes the rearrangement of atoms of a substrate, converting it into an isomer
• What is the function of a ligase enzyme?

  Catalyzes the bonding together of two molecules into one using ATP
• What factors affect enzyme activity?

  • Temperature
  • pH
  • Substrate concentration
  • Enzyme concentration
• How does temperature affect enzyme activity?

  Higher temperature increases molecular motion, leading to faster reaction rates
• What is the optimum temperature for human enzymes?

  37°C
• What happens to enzymes at temperatures above their optimum?

  They may undergo denaturation
• How does pH affect enzyme activity?

  Changes in pH can lead to denaturation and loss of catalytic activity
• What is the optimum pH for most enzymes?

  Usually between pH 7.0 and 7.5
• What is the optimum pH for pepsin?

  pH 2.0
• What is the optimum pH for trypsin?

  pH 8.0
• How does substrate concentration affect enzyme activity?

  Increasing substrate concentration increases reaction rate until maximum velocity is reached
• What is saturation in enzyme activity?

  When enzymes become fully occupied and each incoming substrate must wait for an empty active site
• What is the turnover number in enzymatic reactions?

  The number of substrate molecules transformed per minute by one molecule of enzyme under optimum conditions
• How does increasing enzyme concentration affect reaction rate?

  It increases the reaction rate by allowing more substrate molecules to be accommodated
• What is competitive inhibition?

  A molecule that resembles the substrate competes for occupancy of the active site
• How can competitive inhibition be reduced?

  By increasing the concentration of the substrate