3.3 Control of Intracellular Function by Enzyme Regulation

• What are the two principal mechanisms by which cells control their functions?

  Genetic regulation and enzyme regulation
• How do intracellular inhibitors or activators affect enzymes?

  They act directly on specific intracellular enzymes
• What is the role of enzyme inhibition in cellular function?

  It prevents the buildup of unused intermediary products
• What type of feedback control does enzyme inhibition represent?

  Negative feedback control
• What happens to the first enzyme in a sequence during enzyme inhibition?

  It undergoes an allosteric conformational change
• What substances are controlled by enzyme inhibition?

  Amino acids, purines, pyrimidines, vitamins
• When are enzymes that are normally inactive activated?

  When needed, such as during ATP depletion
• What role does cyclic adenosine monophosphate (cAMP) play in enzyme activation?

  It activates the glycogen-splitting enzyme phosphorylase
• How does cAMP help control intracellular ATP concentration?

  By activating enzymes that liberate glucose
• How do purines and pyrimidines regulate their own synthesis?

  They inhibit their own enzymes and activate each other's
• What is the result of the cross-feed between purine and pyrimidine synthesis?

  Equal amounts of purines and pyrimidines in cells
• What are the two main regulatory mechanisms for cellular constituents?

  • Genetic regulation
  • Enzyme regulation
• What are the feedback control systems in cellular regulation?

  • Monitor biochemical composition
  • Make corrections as needed
• What external factors can influence intracellular biochemical reactions?

  Substances from outside the cell, like hormones