Enzymes and metabolism

• What are enzymes primarily composed of?

  Proteins
• What is the role of enzymes in biological reactions?

  They act as biological catalysts that speed up reactions without being used up
• What does the induced fit model describe about enzyme activity?


  The active site changes slightly to accommodate the substrate
• What is a competitive inhibitor?


  An inhibitor that competes for the active site of an enzyme
• How does HMG-CoA reductase function in relation to cholesterol?


  It lowers blood cholesterol levels
• What is a non-competitive inhibitor?

  An inhibitor that binds reversibly to the allosteric site
• What effect does a non-competitive inhibitor have on the active site?

  It changes the shape of the active site so the substrate can't bind
• What regulates hexokinase in metabolic reactions?


  Glucose 6-phosphate
• What are intracellular enzyme-catalyzed reactions?

  Metabolic reactions that take place inside the cell by enzymes produced by free ribosomes
• Which metabolic processes are examples of intracellular enzyme-catalyzed reactions?

  Glycolysis and the Krebs cycle
• What are extracellular enzyme-catalyzed reactions?

  Metabolic processes that take place outside the cell by enzymes produced by bound ribosomes
• What is an example of an extracellular enzyme?

  Amylase
• How does the second law of thermodynamics relate to metabolic processes?

  It states that no energy transfer is 100% efficient, generating heat in the process
• How do warm-blooded animals maintain their body temperature?

  They use heat from metabolic reactions to maintain a higher body temperature
• What behavioral adaptations do three-toed sloths use to regulate their body temperature?

  They use behavioral adaptations
• What is a metabolic pathway?


  • A chain (linear) or cycle of linked reactions (cyclical)
  • Catalyzed by enzymes
  • Examples:
  • Linear: Glycolysis
  • Cyclical: Krebs cycle
• What does a rate of reaction graph show for uninhibited enzymes?


  It reaches V max
• How does a competitive inhibitor affect the initial rate of reaction?

  It has a lower initial rate of reaction but still reaches V max
• What is the effect of a non-competitive inhibitor on the rate of reaction?

  It has a lower initial rate and reaches a different, lower V max
• What is the chemical nature of a competitive inhibitor?

  It is chemically similar to the substrate
• How does a competitive inhibitor bind to an enzyme?

  It binds to the active site
• What happens to the active site when a non-competitive inhibitor binds?

  Binding modifies the active site
• What is end product inhibition?

  Enzymes that catalyze the first reaction of the pathway are allosterically inhibited by the end-product of the pathway
• How does isoleucine affect threonine deaminase?


  Isoleucine binds to the allosteric site, causing a conformational change in the active site
• What is mechanism-based inhibition?

  It is caused by the irreversible binding of the inhibitor to the active site through a covalent bond
• What is an example of mechanism-based inhibition?

  AZT used in treatment for the HIV virus
• How does penicillin function as an inhibitor?


  It binds to transpeptidases, preventing bacteria from building peptidoglycan cell walls
• What is metabolism?


  • A complex network of interdependent and interacting chemical reactions
  • Occurring in living organisms
• What is anabolism?


  • Synthesis of complex molecules from simpler molecules
  • Requires energy
  • Formation of macromolecules from monomers by condensation
• What is catabolism?


  • Breakdown of complex molecules
  • Releases energy
  • Hydrolysis of macromolecules
• What is the structure of enzymes?

  They are highly specific, complex globular proteins with an active site
• What is the role of the active site in enzymes?


  It is a specific area of a few amino acids where reactions take place
• How do enzymes typically function in terms of their environment?

  Reactions usually take place in a watery environment
• What is the induced fit model's effect on activation energy?


  It reduces activation energy when the substrate binds tightly
• What are endotherms?


  Animals that maintain a constant body temperature