Flashcards in Lecture 31: TCA Cycle Regulation Deck (34)
What are the two main checkpoints for regulation in the TCA cycle?
-Pyruvate Dehydrogenase Complex
What are the two additional regulated reactions?
-alpha-ketogluterate dehydrogenase complex
What do all four regulated reactions have in common?
-keep the cycle going in a clockwise direction usually
What happens if the four regulated steps are slowed?
the whole cycle will be slowed
What effectors are associated with energy-rich state of the cell?
High concentrations of:
What effectors are associated with energy-poor state of the cell?
-because they are substrates or they work through allosteric effects
What inhibits the Pyruvate Dehydrogenase Complex?
What activates the pyruvate dehydrogenase complex?
What inhibits reaction 1 of TCA cycle?
What activates reaction 1 of TCA cycle?
What activates reaction 3 of TCA cycle
What inhibits reaction 3 of TCA cycle
What activates reaction 4 of TCA cycle?
What inhibits reaction 4 of TCA cycle
What is an allosteric activator of 3 of the four regulated steps? and which steps?
What regulates the Pyruvate Dehydrogenase complex activity? Explain
In mammals (not in smaller eukaryotes or prokaryotes) Phosphorylation of the E1 subunit
-There is a kinase activity that can either put on or off the E1 subunit a phosphate
-The kinase and phosphatase activites are controlled by the metabolites associated with energy wealth or poverty (ANTOEHR WAY TO CONTROL PDH)
-NAD+, CoA, ADP, and pyruvate inhibit the kinase so the PDH complex is active
-NADH, Acetyl-CoA induce the kinase, so the PDH complex becomes more phosphorylate and is inactive
What activates the activity of the E2 subunit of the pyruvate dehydrogenase complex?
What inhibits the activity of the E2 subunit of the pyruvate dehydrogenase complex?
What activates the activity of the E3 subunit of the pyruvate Dehydrogenase complex?
What inhibits the activity of the E3 subunit of the pyruvate dehydrogenase complex?
What are two problems associated with the TCA cycle?
1)the cycle has to have a way to run without buildup or depletion of intermediates even if there is extensive injection or withdrawal of different components
2)Most of the catabolic and anabolic reactions take place in the cytoplasm. The TCA cycle takes place in the inside the inner membrane of the mitochondrial matrix from pyruvate onwards. THERE ARE NO TRANSPORT CHANNELS FOR ALL OF THE COMPOUNDS
What input channels exist for the TCA cycle allowing metabolites in?
NOT OXALOACETATE AND ACETYL-COA
What output channels exist for the TCA cycle allowing metabolites out?
What is the reason why a high amount of metabolites would enter the TCA cycle?
Catabolism of carbohydrates or fatty acids
What happens if there isn't any carbohydrate available due to the conversion of pyruvate to fatty acids?
-deficiency of acetyl-CoA entering the citric acid cycle. Therefore oxaloacetate can exceed its normal concentration in the mitochondrion and will be exported
the reactions that replenish the metabolites in the citric acid cycle
What is the main anaplerotic reaction?
replenishment of oxaloacetate
Transporter for pyruvate
-need another way for export or another metabolite of its equivalent
-PEP Transporter! for export
Transporter for acetyl-CoA
None for export
-Citrate can be formed with a reaction of oxaloacetate which can be exported
-once citrate is exported into the cytoplasm-its decomposed to oxaloacetate and acetyl-CoA by the enzyme ATP-citrate lyase