18.6 respiratory substrates

how are triglycerides used as a respiratory substrate

• they are hydrolysed to fatty acids which enter the krebs cycle via acetyl CoA and glycerol

• glycerol is first converted to pyruvate before undergoing oxidative decarboxylation, producing an acetyl group which is picked up by coenzyme A, forming acetyl CoA

relative energy release amounts

lipids store and release 2x the energy of carbs

proteins are similar to carbs

alcohol is a bit more than carbs

how are proteins used as a respitory substrate

• hydrolysed to amino acids

• the amino acids have to be deaminated before they enter the respiratory pathway usually via pyruvate

• these steps require ATP reducing the net production of ATP

respiratory quotient

volume of CO2 produced/ volume of O2 comsumed