enzymes ocr

• enzymes are globular proteins with complex tertiary structures.
• metabolic pathways are controlled by enzymes in a biochemical cascade of reactions, therefore enzymes are essential for life
• intracellular enzymes: produced and function inside the cell
• extracellular enzymes: secreted by cells and catalyse reactions outside cells
• induced fit hypothesis?

  • enzyme and its active site change shape (conformational changes)
  • ensures an ideal binding arrangement
  • maximises ability of enzyme to catalyse reaction
• how can hydrogen and ionic bonds within an enzyme break?

  if in solutions with excess H+ ions or OH- ions

  (enzymes adapt their optimum pH to its functional environment)
• why do lower temps either prevent reactions or slow them down?

  1. molecules move relatively slowly due to less kinetic energy

  2. results in lower frequency of successful collisions so less enzyme-substrate complex formation

  3. substrate and enzyme also collide with less energy (bond breaking or formation less likely).
• how can excessively high temps denature enzymes?

  1, increased kinetic energy and vibration of enzyme puts a strain on the weaker H and ionic bonds.

  2, causes them to break, therefore the enzymes precise shape falls apart

  3, tertiary structure changes

  4, active site permanently damaged and no longer complementary.
• the higher the enzyme concentration in a reaction mixture, the greater the number of active sites available and greater the likelihood of enzyme-substrate complex formation.
• if the amount of substrate is limited, at a certain point any increase in enzyme conc will not increase the reaction rate as amount of substrate becomes limiting factor.
• the greater the substrate conc, the higher the rate of reaction as likelihood of enzyme-substrate complex formation increases
• some enzymes are inactive until they combine with a non-protein structure (cofactor) that changes their tertiary structure (allowing the active site to bind with substrate)
• what are larger organic cofactors called?

  coenzymes
• coenzymes are involved in carrying electrons or chemical groups, aiding in catalysis. this is occurs during metabolic processes where the coenzyme links different reactions.
• what are prosthetic groups?

  permanent cofactor that becomes part of the enzyme structure
• why are prosthetic groups essential to their enzyme?

  they help to form the final 3D shape of the enzyme and therefore their complementary active site.