1 (key concepts) - exam qs

• At which stage does protein synthesis take place?

  Translation
• Where do amino acids join together?

  Ribosomes
• Explain the role of the active site of an enzyme

  Active sites have a specific shape and it binds to a substrate. It is for a reaction to take place.
• Why does phenolphthalein turn colourless when lipase breaks down the lipids in milk?

  Fatty acids are formed when lipids are broken down. This decreases the pH as they are acidic causing the colourless look.
• Explain how the lock and key hypothesis models how enzymes work

  The enzyme and the substrate have complementary shapes and when a substrate fits into an enzyme, an enzyme-substrate complex is formed. The active site is where the substrate fits into. Enzymes break and make bonds to make products.
• Explain how temperature affects enzyme-catalysed reactions:

  If the temperature is too low, there is insufficient energy to make reactions occur. In humans, the optimum temperature for enzymes to work at, is 37 degrees, anything above changes the shape of the enzyme so the rate of reaction decreases as enzyme denatures
• Explain how pH affects enzyme-catalysed reactions:

  The optimum temperature is around 7 and a pH on either side of the optimum changes the shape of the enzyme, therefore the rate of reaction decreases as the enzyme denatures.
• Explain how substrate/enzyme concentration affects enzyme-catalysed reactions:

  Higher concentrations mean more collisions until all enzymes are used therefore a faster rate of reaction