Question

When the human body is subjected to prolonged starvation, cells use up all available glucose first, including glucose bound up in glycogen. When all glucose has been depleted, cells use lipids as a fuel source, and when lipids have been depleted, cells use proteins as a fuel source. Throughout these shifts to new fuel sources, the enzymes of glycolysis and the citric acid cycle remain present and active in the cells. Which statement explains the constancy of these enzymes under conditions of starvation?

Answer 1

The options are missing from the question. They are;

a. These enzymes are inhibited but not destroyed under conditions

of starvation since destroying them would require energy input.

b. These enzymes continue to be needed since catabolism of lipids

and proteins leads to intermediates that are oxidized through

these pathways.

c. Once enzymes are produced in a cell, they continue to function

for as long as the cell lives even if they are not used.

d. All catabolic enzymes are expressed when energy levels are low

in a cell, including enzymes that cannot oxidize the fuel

molecules that are available.

e. The cell continues to produce these enzymes in case glucose or

other carbohydrates become available again.

The correct answer to the question is option B

THESE ENZYMES CONTINUE TO BE NEEDED SINCE CATABOLISM OF LIPIDS AND PROTEINS LEADS TO INTERMEDIATES THAT ARE OXIFIZED THROUGH THESE PATHWAYS.

The enzymes involved in glycolysis are; hexokinase, phosphofructokinase, and pyruvate kinase.

The cell use Amino acids as energy source through the conversion of the amino acids that enter glycolysis or the citric cycle that are eventually catabolized to CO2 at various points through the help of their enzymes (fumarase) or (fumarase hydratase) speeding up the rate of the reaction.(pyrimidines).