Respiratory substrates

• How is RQ calculated?

  by dividing the volume of carbon dioxide released by the volume of oxygen taken in during the respiration of that particular substrate.

  RQ = carbon dioxide produced / oxygen consumed
• what is the RQ of glucose?

  1
• why do lipids produce so much more ATP in respiration?

  • they have a greater proportion of C-H bonds than carbs
  • so they require more oxygen to break them down and release relatively less carbon dioxide
  • therefore lipids have a lower RQ that carbs (0.7)
• state the RQs of carbs, lipids and proteins

  • carbs- 1
  • proteins- 0.9
  • lipids- 0.7
• True or false, glucose can be used to form pyruvate, but not triglycerides and AAs

  FALSE!- glucose, AAs and fatty acids can all be used to form pyruvate and assist in the krebs cycle

  
• Where does alcohol lie in terms of RQ compared to carbs and lipids?

  • More energy than carbs
  • Less energy than lipids
• what is the RQ range during exercise? why is this?

  • in the range 0.8-0.9
  • showing carbs lipids and probs some proteins are being used
• what happens to RQ during anaerobic respiration? why is this?

  increases above 1.0
• What can be used to measure RQ?

  A respirometre
• True or false? proteins are roughly equivalent to carbs in how much energy they produce

  TRUE
• when does RQ rise above 1?

  during anaerobic respiration
• what does a respirometer measure?

  changes in oxygen or carbon dioxide
• what does KOH do in a respirometer?

  absorbs carbon dioxide
• describe how a respirometer is used

  
  

  The higher the rate of respiration, the more the coloured liquid moves.

  
  

  METHOD:

  • Two tubes, one containing the living organisms and the other with glass beads as a control with no insect in order to compare results. Both tubes contain an alkali such as sodium hydroxide to absorb any carbon dioxide. Ensures that any volume changes measured in the experiment are due to oxygen uptake only.
  • The movement of the coloured liquid towards the insect will give a measure of the volume of oxygen taken up by the insect for respiration.
  • The reduction of volume in the tube increases pressure causing the coloured liquid to move.
  • distance moved by the liquid in a given time is measured. Provides the volume of oxygen taken in by the insect per minute.
  • Volume is given by volume of a cylinder V=πr2h, where h is the distance moved by the coloured liquid. The unit of rate of respiration is cm3/min.