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Cellular Respiration and Biomolecular

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Choose one example of inhibition that is found in either glycolysis or the citric acid cycle.Explain if your example is a process of feedback inhibition or allosteric activation. After evaluating the necessary functions in cellular respiration, you will need to employ a little imagination to suggest a real life situation that parallels the inhibition or regulation you described above.
In addition to its role in catabolism, the citric acid cycle also plays an important role in cellular anabolism, or biosynthetic reactions. Many of the citric acid cycle intermediates are precursors for the synthesis of amino acids and other macromolecules required by the cell.
a. Describe the biomolecule that you think is most important for the cell and why?
b. After evaluating the biomolecules used by our bodies for a variety of functions employ your imagination to suggest a real life situation that exemplifies an anabolic reaction.

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Solution Summary

The material above explains the various regulations (allosteric inhibition, feedback inhibition) operating in the Citric Acid Cycle. Also explained is the role citric acid cycle as being an Anabolic process giving rise to precursors of various biomolecules. Real life examples of anabolism and feedback inhibition are also provided. References are provided backing the claims made here.

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The citric acid cycle must be carefully regulated by the cell. If the citric acid cycle were permitted to run unchecked, large amounts of metabolic energy would be wasted in the over production of reduced coenzymes and ATP. Conversely if the citric acid cycle ran too slowly, ATP would not be generated fast enough to sustain the cell.
The citric acid cycle is regulated by three simple mechanisms.
1. Substrate availability
2. Product inhibition
3. Competitive feedback inhibition.

1. Substrate Availability: The rate of flow through the citric acid cycle can be limited by the availability of the citrate synthase substrates, oxaloacetate and acetyl-CoA, or of NAD+, which is depleted by its conversion to NADH, slowing the three NAD-dependent oxidation steps.

2. Allosteric Inhibition: The PDH (Pyruvate Dehydrogenase) complex/Citric acid cycle is allosterically inhibited when [ATP]/[ADP], [NADH]/[NAD+], and [acetyl-CoA]/[CoA] ratios are high, indicating an energy-sufficient metabolic state. When these ratios decrease, allosteric activation of pyruvate oxidation results.

3. Competitive Feedback inhibition by succinyl-CoA, citrate, and ATP also slows the cycle by inhibiting early steps.

Figure 1: Showing the different types of regulation of citric acid cycle (Lehninger, A. L. ...

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