A2 bio respirometer

[zahraahmed]

can someone tell me how is it possible to measure CO2 consumption using a respirometer
respirometers use co2 absorbents such as soda lime so how are we supposed to measure vol of co2 released
during respiration so that a RQ value can be calculated.
Thnkx in advance :roll:

 

[beacon_of_light]

First of all oxygen uptake is measured in the presence of soda lime at a particular temperature. Let's say it's "x" ...
Then remove soda-lime. But this time when organism respires, it consumes oxygen and releases carbon dioxide. If oxygen consumption= carbon dioxide release, then the manometers level will balance and RQ = 1 .
Say, if "y" more carbon dioxide is released than oxygen absorbed (x) , then RQ = (y+x)/ x

If the carbon dioxide released is y cm^3 less than oxygen, then RQ = (x-y)/x

Hope that helps!

 

[zahraahmed]

thanks; can you please explain this: is co2 released measured by the capillary U tube (manometer scale) or is it measured by the 1 cm^3 syringe just above the control tube; I am referring to Fig 15.19 page 209 in black mary jones a level bio book :?

 

[beacon_of_light]

Ur welcome

Well the syringes are just used to restore the original volume of air in the apparatus before the start of another experiment! It is actually the manometer fluid levels in both tubes... or say capillary U tube!