Explain in details Aerobic Respiration?
The pyruvate produced in glycolysis is further broken down in most organisms. This process, called aerobic respiration, requires gaseous oxygen and yields far more energy than glycolysis. Aerobic respiration is divided into two processes: the Krebs cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation. The chemical reactions that occur can be summarized as follows:
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy
Krebs cycle
The Krebs cycle is a series of chemical reactions that dismantles pyruvic acid molecules, and removes energy remaining in its chemical bonds. This energy is then converted into a usable form by the electron transport chain. Matrix, the protein-rich fluid enclosed by the inner membrane.
Prior to entering the Krebs Cycle, pyruvate is converted to acetyl CoA. This conversion involves the removal of a CO2 molecule to make acetyl, and the loss of electrons (oxidation) to NAD+, forming NADH, a high energy electron carrier molecule. An enzyme called coenzyme A is combined with the remaining acetyl to make acetyl CoA which is then fed into the Krebs Cycle. The steps in the Krebs Cycle are summarized below:
(1) The acetyl group from acetyl CoA combines with oxaloacetate from the Krebs cycle to form citrate.
(2) Citrate restructures itself to form isocitrate, an isomer of citrate.
(3) Isocitrate is oxidized to form the 5-carbon a-ketoglutarate, releasing one molecule of CO2, and reducing NAD+ to NADH + H+.
(4) The a-ketoglutarate is oxidized to succinyl CoA, yielding CO2 and NADH + H+.
(5) Succinyl CoA releases coenzyme A in a process that converts ADP to ATP.
(6) Succinate is oxidized to fumarate, converting FAD to FADH2.
(7) Fumarate combines with H2O to form malate.
(8) Malate is oxidized to oxaloacetate, reducing NAD+to NADH + H+.
The cycle has now returned to the beginning. Since glycolysis produces two molecules of pyruvate from one molecule of glucose, the Krebs cycle is entered twice for each molecule of glucose, and produces six NADH + H+, two FADH2, and two ATP. Note that glycolysis and the Krebs cycle together yield only a net of 4 molecules of ATP, which are produced directly through what are referred to as substrate phosphorylations. This amounts to less than 4 percent of the total energy available in the glucose molecule.