TCA Cycle Flashcards
Why is the Pyruvate Dehydrogenase reaction considered an oxidative decarboxylation?
Carbonyl on pyruvate attacked by acetyl-CoA and removed
What cofactors/co-enzymes are involved and what are their roles?
TPP - coenzyme form of vitamin B1
lipoic acid
FAD
What is the role of FAD?
Responsible for accepting “high energy” electrons and carrying them ultimately to the electron transport chain where they are used to synthesize ATP molecules.
How is NADH produced? Can acetyl-CoA be converted directly back to glucose by this enzyme? What other enzyme in the TCA cycle uses similar chemistry?
NADH generated in cytoplasm during glycolysis, reduced version of NAD+
Irreversible - acetyl-CoA cannot be converted directly back to glucose
What does any dehydrogenase do? What is used, what is produced?
Mediates in biochemical reactions by removing hydrogen atoms [H] instead of oxygen [O] (oxidizes a substrate by reducing an electron acceptor)
Produces an oxidized molecule
What is the role of the TCA cycle in energy production? Why is this role active in aerobic conditions? Why or why not?
TCA cycle releases available energy from acetyl-CoA to make NADH used to reduce molecules
Cycle aerobic b/c need to regenerate e- carriers, e- must transfer to O2 (final e- acceptor in ETC)
How does the TCA cycle produce energy? Does it directly produce any ATP? In the absence of oxygen, what is produced?
ATP is directly produced from TCA cycle
Nothing is produced in absence of oxygen
How is the TCA cycle regulated? What compounds are “sensed” by which enzymes?
Cycle regulated by ATP and NADH levels (high level, cycle slows)
Regulation by enzymes that make NADH: isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase
What is the role of the TCA cycle enzymes in anaerobic bacteria? How do these bacteria produce energy?
Modified TCA cycle to produce CO2
Bacteria produce energy through oxidation of compounds
What is the Warburg effect? How is it explained?
Tumor cells produce lactate even in presence of oxygen (aerobic glycolysis), assumed to be caused by defect in mitochondrial respiration in tumor cells
Why would rapidly dividing cells NOT use aerobic respiration for energy?
The cell has chosen to produce less energy in return for being able to produce more biomass
Using aerobic respiration for other uses
What is the glyoxylate pathway and why is this important for plants? What advantage does this give plants in terms of using fats to build carbohydrates?
How does the TCA cycle contribute to DNA synthesis? To protein synthesis?
How do DNA and protein degradation contribute to the TCA cycle? Gluconeogenesis?
What is meant by an anaplerotic reaction? Why do vertebrates need these reactions and when?
