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CHM 462C Exam 2
Biochemistry of TCA Cycle and Respiration
Question | Answer |
---|---|
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 |