L3.2 Protein Metabolism

Question 1

How is the level of protein metabolism measured?

Answer 1

• Measure O2 consumption & CO2:
  
  • By labelling substrates using stable isotopes

Question 2

What is the protein contribution of energy?

Answer 2

• Contributes 50%, but muscle system is only 25% effective
  
  • ∴only contribute 12.5% of energy

Question 3

What is the glucose-alanine cycle?

Answer 3

• Muscle → breakdown glucose → pyruvate → alanine → Liver → (Deanimation into urea) & (alanine → pyruvate) → glucose → back to muscle

*Protein is the main determinant of urea production*

Question 4

AA acids enter the TCA cycle at different points by producing different intermediates.

At what point does glutamate and Leucine enter?

Answer 4

• Pyruvate + glutamate → alanine + α-ketoglutarate
  
  • Important to have ↑[glutamate] before exercise → allows cycle to form more oxaloacetate to couple with acetyl-CoA (from FA & CHO metabolism) & citrate for cycle to proceed
• Leucine → Acetyl-CoA
• Oxidation rate of AA are different

Question 5

What happens to AA metabolism when other sources of fuels are limited?

Answer 5

↑AA oxidation