Understanding Respirometers in Biological Experiments

Simple Respirometer Advantages: Simpler to set up Minimal number of connections makes a good seal easier to obtain.

Respiration rate Respirometer results Time (Min) 0 1 2 3 4 5 Column of liquid (cm) 0 0 1.1 1.6 1.9 2.7 1 1.2 1.4 1.5 1.6 1.8 0 0.4 1.1 1.5 Average 0.53 1.2 1.53 1.75 2.25 After 5 minutes the creatures had used 2.25 cm length of liquid. Volume of liquid used is Pi x r2 x h . H= 2.25 cm. R is in cm. (0.05) Calculate the volume. Rate of respiration = x cm3 O2 g-1 h-1. (for 10 creatures).

The more complex respirometer Limitations of simple respirometer: Changes in temp or pressure affect the volume of the gases. The chemicals used might affect the composition of the gases. It is difficult to restart the without taking the apparatus apart. The volume change calculated using the diameter of the tube may be inaccurate.

http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpghttp://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg When the liquid moves it can be reset to its original position by puling up the syringe. The volume increase inside the syringe then equals the amount of oxygen used. It can be measured easily and is more accurate as does not involve a diameter measurement. The tube on the right acts as a control because any changes in the liquid level due to temperature change or pressure change are balanced out. The respirometer can also be reset easily.

Disadvantages of the more complex respirometer Tendency for the connections to leak. More expensive.

Respirometer calculations A more complex respirometer was set up with 50g of blowfly larvae (bluebottle) and left for 1 hour. The fluid moved up the left-hand side of the U-tube by 5 cm. It was moved back to its original level by drawing 2 cm 3 of air into the syringe. a. What was the purpose of the syringe and why does it give this respirometer an advantage over the simple respirometer? b. If there were 10 larvae what was the respiratory rate per organism? c. Assuming that the blowfly larvae are only respiring one substrate, suggest which one. d. From what you know about the diet of these larvae is it a reasonable assumption that they only respire one substrate? e. How does the addition of a control tube (called a thermobar), help to overcome the problem of changes of atmospheric temperature and pressure?

Respiration of fats and proteins http://furtherglory.files.wordpress.com/2011/04/youngsurvivor.gif http://www.sabotagetimes.com/wp-content/uploads/fat_person_in_boat.jpg

Respiration of fats When carbohydrates are in short supply then lipids can be broken down to fatty acids and glycerol. Fatty acids are further broken into acetyl fragments and combined with Coenzyme A enter the Krebs cycle. Glycerol can enter glycolysis.

Respiration of proteins Need 60g a day of protein Cannot store it Excess protein broken down to amino-acids in the liver. Amine group separated and goes to form urea. The organic acids that are left are fed into the Kreb s cycle and respired.

Questions 1. Make a table to show where the products from lipid and protein breakdown can be respired. 2. The Atkins diet claims to reduce weight by sticking to a high protein diet. Explain how this might help people lose weight.