Question

4 molecules of ATP are generated by glycolysis. However, the net products of glycolysis are 2 ATP, 2 pyruvate, and 2 NADH molecules. The ATP values do not match because?

1) ATP is consumed during the process of glycolysis
2) ATP is not directly produced by glycolysis
3) There is an error in the calculation of ATP production
4) ATP is converted into another form of energy during glycolysis

Answer 1

A net production of two ATP molecules occurs during glycolysis, but these ATP molecules are used for transporting NADH produced during glycolysis into the mitochondria. Therefore, the net production of ATP during glycolysis is zero. The ATP production increases in subsequent phases after glycolysis.

Step-by-step explanation:

A net of two ATP are produced through glycolysis (four produced and two consumed during the energy-consuming stage). However, these two ATP are used for transporting the NADH produced during glycolysis from the cytoplasm into the mitochondria. Therefore, the net production of ATP during glycolysis is zero.

In all phases after glycolysis, the number of ATP, NADH, and FADH2 produced must be multiplied by two to reflect how each glucose molecule produces two pyruvate molecules.

In the ETC, about three ATP are produced for every oxidized NADH. However, only about two ATP are produced for every oxidized FADH2. The electrons from FADH₂ produce less ATP, because they start at a lower point in the ETC (Complex II) compared to the electrons from NADH (Complex I) (see Figure 24.8).