In the mammalian CNS there is a pyridoxal phosphate dependent glutamate decarboxylase that catalyzes the conversion of glutamate to gamma-amino butyric acid (GABA). This is an important inhibitory neurotransmitter.
GABA is subsequently degraded through transamination to succinic semialdehyde, with alpha-ketoglutarate as the NH3+ acceptor.
The succinic semialdehyde can then be oxidized to succinate, by succinate dehydrogenase.
a. Show how these reactions can operate as a shunt pathway that allows the TCA cycle to function without alpha-ketoglutarate dehydrogenase and succinate thiokinase.
b. Is the shunt more or less efficient than the TCA cycle in terms of energy recovery?
Show how these reactions can operate as a shunt pathway that allows the TCA cycle to function without alpha-ketoglutarate dehydrogenase and succinate thiokinase."
In other words, normally, in the TCA, alpha-ketoglutarate is converted to succinyl-CoA, which is further converted to succinate. The two enzymes that do this are alpha-ketoglutarate dehydrogenase and succinate thiokinase. However, the GABA shunt bypasses these two enzymes and provides a way for the TCA to function without them. Therefore, we need to show that alpha-ketoglutarate can be converted to succinate through this GABA shunt.
Here's now it works:
The amino acid glutamate acts as the shuttle, being ...
This solution includes a detailed discussion of (a) and (b) and a GABA shunt diagram. 420 words.
Cellular respiration and Biomolecular
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.