A-Level practicals (Y2)

• Which organism is used in the respiration practical?

  Yeast
• What enzyme is focused on in the respiration investigation?

  Dehydrogenase
• What does dehydrogenase do in respiration?

  Removes hydrogen from coenzymes and compounds
• What coenzyme is mentioned that picks up hydrogen?

  NAD
• What happens to NADH in oxidative phosphorylation?

  It splits into electrons and protons
• What is the role of TTC in the experiment?

  It acts as an artificial hydrogen acceptor
• What color change indicates the reaction is occurring with TTC?

  Colorless to red precipitate
• What variable is being investigated in relation to enzyme activity?

  Temperature
• How does temperature affect enzyme activity according to the video?

  Increased temperature raises kinetic energy
• What is the hypothesis regarding yeast and TTC's color change?

  It will turn red faster with higher temperatures
• What temperatures are used in the respiration experiment?

  20°C, 30°C, 40°C, 45°C, 50°C
• Why must the solutions be left in the water bath for five minutes?

  To equilibrate to the test temperature
• What is the endpoint for the reaction indicated by TTC?

  When the solution reaches a specific shade of pink
• What is the significance of stirring the solution during the experiment?

  To prevent yeast from settling at the bottom
• How is the rate of reaction calculated in the experiment?

  By dividing 1000 by time
• What statistical test is suggested for analyzing the results?

  Spearman's rank correlation
• What limitation is mentioned regarding the color change measurement?

  It is subjective and can vary between observers
• What issue arises from taking test tubes out of the water bath?

  The temperature may drop during observation
• At which stages of respiration does dehydrogenase remove hydrogen?

  Glycolysis and Krebs cycle
• Why is it ideal to use a see-through thermostatic water bath?

  To observe color change without removing samples
• What are the steps involved in the respiration practical using yeast and TTC?

  1. Prepare yeast and glucose solution.
  2. Prepare TTC solution.
  3. Equilibrate both solutions in water baths.
  4. Mix solutions and start timing.
  5. Observe color change to determine endpoint.
  6. Record time taken for color change.
• What are the limitations of the respiration practical experiment?

  • Subjectivity in color change assessment
  • Temperature drop when removing test tubes
  • Need for a clear view of color changes
• What are the expected results of the experiment regarding temperature and reaction rate?

  • Rate of reaction increases with temperature
  • Time taken for color change decreases
  • Higher temperatures lead to faster reactions
• Who is the instructor for the A-level biology video?

  1. Drake
• What is the focus of the practical discussed in the video?

  Investigating dehydrogenase activity in chloroplasts
• What is the name of the practical being discussed?

  Investigating the rate of dehydrogenase activity
• What variable is being changed in the experiment?

  Ammonium hydroxide
• What is the expected effect of ammonium hydroxide on dehydrogenase activity?

  It may decrease or stop the activity
• What is the role of dehydrogenase enzyme in chloroplasts?

  Catalyzes reactions involved in NADP
• What does DCIP stand for?

  Not specified in the material
• What is the color change of DCIP when it is reduced?

  Turns colorless
• Why is ammonium hydroxide used in the experiment?

  To investigate its effect on enzyme activity
• What is the purpose of the control experiments?

  To validate the experimental results
• What is the purpose of the first test tube in the experiment?

  To serve as a standard for comparison
• What does the foil covering in the control experiment demonstrate?

  Light is required for decolorization
• What does an isotonic solution prevent?

  Osmosis that could damage chloroplasts
• What happens to the chloroplasts if the solution is not isotonic?

  They may burst or shrivel
• How does ammonium hydroxide affect the light-dependent reaction?

  It slows down or stops the reaction
• What is the relationship between the light-dependent reaction and ATP production?

  ATP is produced during the light-dependent reaction
• What is the time taken for the first experimental tube to change color?

  7 minutes 44 seconds