Question

The starting molecule for the Krebs cycle is

Select one:
a. glucose.
b. NADH.
c. pyruvic acid.
d. coenzyme A.

Answer 1

The Krebs cycle begins with pyruvic acid, which is converted to acetyl CoA before entering the cycle. One turn through the cycle produces one molecule of ATP and multiple molecules of NADH and FADH2, with FADH2 production specific to the Krebs cycle.

Step-by-step explanation:

The starting molecule for the Krebs cycle is pyruvic acid (c). After glycolysis, pyruvic acid is transformed into acetyl coenzyme A (acetyl CoA) which then enters the Krebs cycle by combining with oxaloacetate. During one turn of the Krebs cycle, one molecule of ATP is produced, along with multiple molecules of NADH and FADH2. The production of FADH2 is unique to the Krebs cycle, distinguishing it from other stages of cellular respiration.