Products of the Krebs Cycle
The products of the Krebs cycle (also known as the citric acid cycle or TCA cycle) for each turn of the cycle are:
- 3 NADH (Nicotinamide adenine dinucleotide)
- 1 FADH₂ (Flavin adenine dinucleotide)
- 1 GTP (or ATP, depending on the specific cell type)
- 2 CO₂ (Carbon dioxide)
Since each glucose molecule produces two acetyl-CoA molecules (it takes two turns of the Krebs cycle for each glucose), the total products from one glucose molecule will be:
- 6 NADH
- 2 FADH₂
- 2 GTP (or ATP)
- 4 CO₂
Overall Task of Stage III of Aerobic Respiration
Stage III of aerobic respiration refers to the Electron Transport Chain (ETC) and oxidative phosphorylation. The overall task of this stage is to use the electrons harvested from NADH and FADH₂ (which are produced in previous stages, such as the Krebs cycle) to create a proton gradient across the inner mitochondrial membrane. This gradient powers ATP synthase, ultimately generating ATP through chemiosmosis. Additionally, oxygen acts as the final electron acceptor, forming water as a byproduct.
Maximum Number of ATP Molecules from the Electron Transport Stage
The maximum number of ATP molecules that can be produced during the electron transport stage of aerobic respiration is generally estimated to be around 28 to 34 ATP. The actual amount can vary based on the efficiency of the ATP synthase, the transport of electrons, and the proton gradient, among other factors. Typically:
- Each NADH can yield approximately 2.5 to 3 ATP.
- Each FADH₂ can yield approximately 1.5 to 2 ATP.
Thus, if you consider all NADH and FADH₂ produced from one molecule of glucose (6 NADH and 2 FADH₂), the total ATP yield from oxidative phosphorylation alone can vary depending on these factors.
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