According to the diagram below, what happens to the four atoms that begin the citric acid cycle in oxaloacetate?
A) All four atoms continue around the cycle over and over again.
B) Two of the atoms continue around the cycle a second time and two atoms are released from the cycle.
C) One of the atoms continues around the cycle a second time and three atoms are released from the cycle.
D) Three of the atoms continue around the cycle a second time and one atom is released from the cycle.
E) All four atoms are released from the cycle.

Question

According to the diagram below, what happens to the four atoms that begin the citric acid cycle in oxaloacetate? 
A) All four atoms continue around the cycle over and over again. 
B) Two of the atoms continue around the cycle a second time and two atoms are released from the cycle. 
C) One of the atoms continues around the cycle a second time and three atoms are released from the cycle. 
D) Three of the atoms continue around the cycle a second time and one atom is released from the cycle. 
E) All four atoms are released from the cycle.

Quizplus · Accepted Answer

Two of the four carbon atoms in oxaloacetate are removed as CO2 during the citric acid cycle, while the other two carbons are incorporated into other molecules in the cycle. Thus, two of the original atoms continue around the cycle a second time, while two atoms are released from the cycle.

According to the Diagram Below, What Happens to the Four