For each molecule of glucose entering respiration:
a) How many ATP are produced during the Krebs cycle?
b) How many NADH are produced during the Krebs cycle?
c) How many FADH, are produced during the Krebs cycle?
d) How many molecules of carbon dioxide are produced during the Krebs cycle??
The correct answer and explanation is :
Answers:
a) 2 ATP are produced during the Krebs cycle.
b) 6 NADH are produced during the Krebs cycle.
c) 2 FADH₂ are produced during the Krebs cycle.
d) 4 CO₂ molecules are produced during the Krebs cycle.
Explanation:
Cellular respiration is a multi-step process that converts glucose into energy. The Krebs cycle (also called the citric acid cycle or TCA cycle) is a crucial part of aerobic respiration, occurring in the mitochondrial matrix. This cycle processes acetyl-CoA, which is derived from pyruvate, the product of glycolysis.
For each molecule of glucose (C₆H₁₂O₆), two molecules of pyruvate are produced, and each pyruvate is converted into one acetyl-CoA. Since the Krebs cycle operates once per acetyl-CoA, it occurs twice per glucose molecule.
- ATP Production: During one turn of the cycle, one ATP (or GTP) is produced through substrate-level phosphorylation. Since the cycle turns twice per glucose, this results in 2 ATP per glucose.
- NADH Production: Each turn of the cycle generates three NADH molecules through redox reactions. Since the cycle happens twice per glucose, this results in 6 NADH per glucose. These NADH molecules are crucial for ATP production in the electron transport chain.
- FADH₂ Production: Each turn of the cycle produces one FADH₂, leading to 2 FADH₂ per glucose. FADH₂ also donates electrons to the electron transport chain but at a lower energy level than NADH.
- CO₂ Production: Two carbon atoms from acetyl-CoA are fully oxidized and released as two CO₂ molecules per cycle turn. Since the cycle occurs twice per glucose, a total of 4 CO₂ molecules are released.
Thus, the Krebs cycle plays a fundamental role in energy extraction, producing high-energy electron carriers (NADH, FADH₂) and ATP while fully oxidizing glucose-derived carbon into CO₂.