Question

Which statement is TRUE regarding the late stages of starvation?

A) The brain has decreased its need for glucose by switching to lactate as a major energy source.

B) HIgh levels of acetyl-CoA derived from lipid catabolism lead to the production of acetoacetate.

C) Ketone bodies are produced from amino acids liberated from noncritical proteins.

D) Gluconeogenesis is extremely active in the liver because of the large amounts of lactate exported from the muscle.

E) Catabolism of triacylglycerols provides the major source of a gluconeogenic metabolite in the form of glycerol.

Answer 1

D) Gluconeogenesis is extremely active in the liver because of the large amounts of lactate exported from the muscle.

After several days of fasting, all cells in the body begin to break down protein. This releases alanine and lactate produced from pyruvate into the bloodstream, which can be converted into glucose by the liver. Since much of human muscle mass is protein, this phenomenon is responsible for the wasting away of muscle mass seen in starvation. However, the body is able to selectively decide which cells will break down protein and which will not. About 2–3 g of protein has to be broken down to synthesize 1 g of glucose; about 20–30 g of protein is broken down each day to make 10 g of glucose to keep the brain alive. However, this number may decrease the longer the fasting period is continued in order to conserve protein.

Starvation ensues when the fat reserves are completely exhausted and protein is the only fuel source available to the body. Thus, after periods of starvation, the loss of body protein affects the function of important organs, and death results, even if there are still fat reserves left unused. (In a leaner person, the fat reserves are depleted earlier, the protein depletion occurs sooner, and therefore death occurs sooner.) The ultimate cause of death is, in general, cardiac arrhythmia or cardiac arrest brought on by tissue degradation and electrolyte imbalances.