1) An inner mitochondrial membrane that is leaky to H+ would cause chemiosmosis to stop as there is no longer a gradient of protons between the outside and inside of the membrane. Without this gradient most of the ATP usually produced by cellular respiration cannot be produced, so the body must find other sources of energy, such as fats. This would cause a loss of weight.
2) For every one pyruvate molecule used, three CO2 molecules are produced. Since only one of the carbons in the pyruvate is radioactive, only one (out of three) of the CO2 molecules produced will be radioactive.
