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CHM 462C Exam 2

Biochemistry of TCA Cycle and Respiration

How many enzymes make up the pyruvate decarboxylase system? 3
What enzymes make up the pyruvate decarboxylase system? Pyruvate decarboxylase, dihydrolipyl transacetylase, and dihydrolipoyl dehydrogenase
What are the products of the pyruvate decarboxylase system? Acetyl-Co A, CO2, and NADH (-delta G)
Where does Acetyl-Co A go after its produced? To the citric acid cycle
What happens to oxaloacetate? Oxaloacetate and acetyl-Co A condenses to form citrate via the enzyme citrate synthase
What happens to pyruvate? Pyruvate enters the TCA cycle via acetyl-Co A
What is produced via hydrogenases in the TCA Cycle? 3 NADH and 1 FADH2 molecules
What is produced via oxidative decarboxylation in the TCA cycle? 3 CO2 Molecules
What is produced via substrate level phosphorylation in the TCA Cycle? 1 GTP Molecule
Once citrate is formed, what happens to it? It is converted to isocitrate (by the enzyme aconitase* a dehydration/rehydration) and then is converted to alpha-ketogluterate (by the enzyme isocitrate dehydrogenase)
What happens to alpha-ketoglutarate after it is formed? It is converted to succinyl-Co A (by the alpha-ketoglutarate dehydrogenase complex)
What happens to succinyl-Co A after it is formed? It is converted to succinate (by the enzyme succinyl-Co A synthetase)
What type of chemistry occurs in the conversion of succinyl-Co A to succinate? Substrate level phosphorylation and release of free energy from the Co-A bond that drives the phosphorylation step=drives synthesis of GTP
What happens to succinate after it is formed? It is converted to fumarate (by the enzyme succinate dehydrogenase)
What happens to fumarate after it is formed? It is converted to malate (by the enzyme fumarase)
What happens to malate after it is formed? It is converted to oxaloacetate (by the enzume malate dehydrogenase)
Per pyruvate molecule, what is formed from the TCA Cycle? 3 NADH molecules (4 including pyruvate decarboxylation), 1 FADH2, and 1 GTP molecule
What is significant about the TCA Cycle? There is no net consumption of products from TCA Cycle in the TCA Cycle. It is also an amphibolic pathwath (both catabolic and anabolic chemistry occurs)
How much ATP is produced from the reducing equivalents in the TCA Cycle and oxidative phosphorylation? 32 ATP molecules
How is the TCA Cycle Regulated? By four exergonic (~irreversible) steps (3 occur in the actual pathway)
What four enzymes regulate the TCA Cycle? 1) Pyruvate decarboxylase 2) Citrate Synthase 3) Isocitrate dehydrogenase 4) Alpha-ketoglutarate dehydrogenase complex (the four exergonic steps)
What inhibits and stimulates the Pyruvate Decarboxylase Complex? PDC is inhibited by acetyl-Co A, NADH, ATP, and some fatty acids. It is stimulated by AMP, CoASH, NAD+, and Ca2+
What inhibits and stimulates Citrate Synthase? Citrate Synthase is inhibited by ATP, citrate, NADH, and succinyl-Co A. It is stimulated by AMP
Created by: jgk25



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