Term
| What physiological conditions will inhibit the TCA cycle? Consider the inhibitors. What information are they “giving” about energy? |
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Definition
ATP and NADH will inhibit the TCA cycle, because they are signaling that there is alreay a lot of energy (ATP) so more is not needed right now |
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Term
| What are the major regulatory enzymes of the TCA? How are they regulated? |
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Definition
1. Citrate synthase:
Forms citrate from oxaloacetate and acetyl-CoA
Inhibited by: ATP, NADH, succinyl-CoA (feedback regulation)and long-chain fatty-acyl CoA
2. Isocitrate synthase
Converts citrate to isocitrate
Inhibited by: ATP, NADH
Activated by: ADP
3. a-ketoglutarate dehydrogenase (similiar to PDH)
Converts a-ketoglutarate to succinyl-CoA
inhibited by ATP, GTP, NADH, and succinyl-CoA |
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Term
| What is the point of the TCA cycle? |
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Definition
- Final pathway where the oxidative metabolism of cabohydrates , amino acids and fatty acids converge, their carbon skeletons are converted to CO2
- This oxidation provides energy for most of the ATP in our bodies (via NADH and FADH produced)
- Provides intermediates for many synthetic reactions eg: formation of glucose from carbon skeletons of amino acids (GNG) and building blocks for synthesis of some amino acids
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Term
| What are 2 non-TCA actions of CITRATE? |
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Definition
*use for fatty acid production
*used as an inhibitor for PFK-1 in glycolysis |
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Term
| what are the products of the TCA cycle? |
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Definition
TCA cycle
2 acetyl-CoA --> 4 CO2 + 6 NADH + 2 FADH + ATP (from GTP) |
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Term
| What is the purpose of the pentose phosphate pathway?Where does the PPP occur? |
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Definition
- Make ribose for biosynthesis of nucleotides
- Make NADPH for synthetic reactions and antioxidants
- occurs in cytosol
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Term
| What is the NADPH produced in the PPP used for? |
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Definition
1) Synthesis of fatty acids and steroids
2) Regeneration of reduced glutathione (GSH) in reaction (from GS-SG). This is a very important way of dealing with oxidant damage. Glutathione peroxidase and reducatase are critical in erythrocytes for detoxification of hydrogen peroxide |
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Term
Explain Glucose-6-P dehydrogenase deficiency
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Definition
When people are deficient in this enzyme, they are not able to produce NADPH from glucose-6-phosphate. Without NADPH, reduced gluathione is not able to regenerate.
Glutathione is now unavailble to reduce H2O2 to H20. This causes a build up of H2O2 in cells. The build up causes cells to lyse.Excessive lysing causes a deficiency of RBC (hemolytic anemia) |
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