Answer:
Q: Produces 32 ATP molecules
A: Electron transport chain
Q: Creates four ATP molecules, but then gains overall only two
A: Glycolysis
Q: Gives off carbon dioxide
A: Citric acid cycle or Kreb cycle
Q: Gives off water
A: Electron transport chain
Q: Produces ATP molecules
A: Citric acid cycle or Kreb cycle
Explanation:
1. During oxidative phosphorylation, 32 molecules of ATP are formed. The process takes place in the electron transport chain which has a series of electron transporters that are embedded in the inner matrix of mitochondria. Together, these transporters shuttle the transfer from NADH and FADH2 to molecular oxygen (O2). A detailed calculation of the net production of ATP molecules during oxidative phosphorylation is given in table 1 (attached).
2. Four molecules of ATP are produced during glycolysis but the net gain is only 2 molecules of ATP (2 molecules take part in the glycolysis). Briefly, for one mole of glucose, the net product of glycolysis is as follows: 2 moles of pyruvate, 2 moles of NADH, 4 moles of ATP in which 2 moles of ATP were consumed during glycolysis, 2 moles of water, and 2 moles of protons (H+). For further details, please see figure 2 (attached).
3. During the citric acid cycle (Kreb cycle), two molecules of CO2 are given off as waste gas. The first molecule is produced when a 6-carbon molecule (citrate) is converted to a 5-carbon molecule (ketoglutarate). Likewise, the second CO2 molecule is released when the 5-carbon molecule is converted to the 4-carbon molecule (oxaloacetic acid). To understand further, see diagram 3 (attached).
4. Water is formed in the electron transporter chain to maintain the gradient of H+. We know that the concentration of H+ increases in the intermembrane space and therefore if there is no uptake of H+, the flow of electron will stop which will also stop the formation of ATP. To maintain this flow, the electron transport chain allows, firstly oxygen is reduced which then takes up 2 H+. This leads to the formation of a water molecule.
5. The citric acid cycle also produces an equivalent of an ATP molecule known as a GTP; along with two molecules of CO2, and reduced forms of NADH and FADH2. NADH is an energy shuttle, as described above, and transport high energy electrons to electron transport chain finally leading to the production of 2 ATP molecules (see table 1). It is important to consider that the cycle does not directly consume oxygen and produces very little ATP compared to oxidative phosphorylation.
