ATP Production from VFAs (Acetate, Propionate, Butyrate)

Correct Answer: 10, 17, 25

The ATP yield from complete oxidation of VFAs produced in the rumen:

• Acetate (2C): 10 ATPs — enters TCA cycle as Acetyl-CoA after activation
• Propionate (3C): 17 ATPs — most energy-efficient VFA per carbon; converted to succinyl-CoA via the succinate pathway, entering the TCA cycle
• Butyrate (4C): 25 ATPs — converted to 2 molecules of Acetyl-CoA

Comparison with Other Substrates

• Glucose (aerobic): 38 ATPs
• Glycerol: 22 ATPs
• Palmitic acid: 129 ATPs

1 mole ATP on hydrolysis yields:

7.3 kcal of free energy (ΔG = −7.3 kcal/mol)