Question

In the Cori cycle, A. only tissues with aerobic metabolism (i.e., mitochondria and \(\mathrm{O}_{2}\) ) are involved. B. a three-carbon compound arising from glycolysis is converted to glucose at the expense of energy from farty acid oxidarion. C. glucose is converted to pyruvate in anacrobic tissues, and this pyruvate returns to the liver, where it is converted to glucose. D. the same amount of ATP is used in the liver to synthesize glucose as is released during glycolysis, leading to no net eftect on whole body energy balance. E. nitrogen from alanine must be converted to urea, increasing the amount of energy required to drive the process.

Short answer

Answer: The same amount of ATP is used in the liver to synthesize glucose as is released during glycolysis, leading to no net effect on whole body energy balance.

Step-by-step solution

Option A

This option states that only tissues with aerobic metabolism (i.e., mitochondria and O2) are involved in the Cori cycle. This is incorrect because the Cori cycle also involves anaerobic tissues where glucose is converted to lactate.

Option B

This option states that a three-carbon compound arising from glycolysis is converted to glucose at the expense of energy from fatty acid oxidation. This is incorrect because lactate, a three-carbon compound, is converted to glucose at the expense of energy from ATP produced in the liver.

Option C

This option states that glucose is converted to pyruvate in anaerobic tissues, and this pyruvate returns to the liver, where it is converted to glucose. This is partially correct, as glucose is indeed converted to pyruvate in anaerobic tissues. However, the pyruvate is then reduced to lactate before it returns to the liver, where it is converted to glucose.

Option D

This option states that the same amount of ATP is used in the liver to synthesize glucose as is released during glycolysis, leading to no net effect on whole body energy balance. This is correct. The Cori cycle is energy-neutral as it does not produce or consume net ATP in the body as a whole. The energy released during glucose breakdown in anaerobic tissues is equal to the energy consumed during glucose synthesis in the liver.

Option E

This option states that nitrogen from alanine must be converted to urea, increasing the amount of energy required to drive the process. This is incorrect because the Cori cycle only involves the interconversion of glucose, pyruvate, and lactate, not involving urea or alanine. Hence, the correct statement is Option D.