Term
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Definition
- Also known as Tricarboxylic Acid Cycle (TCA Cycle) and Krebs Cycle
- Takes place in mitochondria
- Utilizes acetyl-CoA, which itself is generated from pyruvate by pyruvate dehydrogenase enzyme
- Each acetyl-CoA generates = 3 NADH, 1 FADH2, and 1 GTP
- NADH and FADH2 are responsible for delivering electrons to Electron Transport Chain to generate energy via oxidative phosphorylation.
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Term
| Equation and Products of TCA |
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Definition
Acetyl-CoA + 3 NAD+ + FAD + GDP + Pi → 2 CO2 + 3 NADH + 1 FADH2 + 1 GTP + CoA
Products: 2 CO2
3 NADH
1 FADH2
1 GTP
CoA |
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Term
Steps in TCA:
Citric Synthase |
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Definition
| first step, inhibited by ATP |
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Term
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Definition
- Rate-limiting enzyme
- Activated by: ADP
- Inhibited by: ATP, NADH
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Term
| . α-Ketoglutarate dehydrogenase |
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Definition
| Inhibited by: Succinyl-CoA, ATP, and NADH |
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Term
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Definition
| In matrix: pyruvate is converted to acetyl CoA (2-C substrate) by the pyruvatedehydrogenase complex (focus on E1) |
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Term
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Definition
| Coenzyme needed by pyruate dehydrogenase in order to be activated |
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Term
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Definition
| Inhibits pyruvate dehydrogenase, allosterically activated by ATP (so ATP activates the inhibitor, making it an indirect antagonist to pyruvate dehydrogenase) |
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Term
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Definition
| Activates phyruvate dehydrogenase, its activity is also increased by Ca2++, stimulating E1 activity |
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Term
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Definition
made from acetyl CoA, and inhibited by its product (citrate)
Once made, it is isomerized by aconitase into isocitrate
Oxidation rxn yields decarboxylation of isocitrate
this is one of rate limiting steps that will yield 1st of 3 NADH molecules
1st release of CO2 |
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Term
| Decarboxylation of ketoglutarate |
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Definition
converted to succinyl CoA
will release 2nd CO2 and 2nd NADH |
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Term
succinyl CoA
succinate
fumarate |
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Definition
cleaved by Succinatethiokinase (yields 1 ATP) to succinate.
Succinate is oxidized to fumarate (by succinate dehydrogenase)
fumarate is hydrated to malate by fumarase |
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Term
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Definition
oxidized to oxaloacetate by malate dehydrogenase.
- makes 3rd and FINAL NADH of cycle |
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Term
Intermediates of TCA Cycle
"Can I Keep Selling Sex For Money, Officer?" |
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Definition
| Citrate- Isocitrate- Ketoglutarate- Succinyl CoA- Succinate- Fumarate- Malate- Oxaloacetate |
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Term
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Definition
•Pyruvate to Acetyl CoA = 1 NADH = 3 ATP
•Steps 3 = NADH = 3 ATP
Steps 4 = NADH = 3 ATP
Steps 8 = NADH = 3 ATP
NET ATP from = NAD+ = 9 ATP
•Step 6 is another oxidation involving the coenzyme FADH2.
Step 6 = FADH2 = 2 ATP
•Step 5 = 1 ATP
15 ATP/Pyruvate * 2= 30 ATP!! |
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Term
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Definition
Glycolysis yields 6 ATP
TCA= 30 ATP
Glycolysis (anaerobic) yields 2 ATP |
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Term
| Conversion of pyruvate to acetyl CoA and CO2 |
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Definition
This is irreversible and involves help from lipoic acid.
Activated when PDH is phosphorylated by PDH kinase in presence of ATP
This also occurs in cytosol and in presence of an enzyme called biotin |
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Term
| Pentose Phosphate Pathway & NADPH |
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Definition
- Pathway that occurs in cytosol
- Involves two reversible oxidative rxns to form sugar phosphate ring molecules that are involved in nucleotide synthesis.
- No ATP is used or made in this process!
- povides most of body's NADPH |
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Term
Pentose Phosphate Path-
Irreversible Oxidative Pathways |
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Definition
that lead to the formation of ribulose 5-phosphate, CO2, and 2 molecules of NADPH for each molecule of glucose 6-phosphate oxidized
Important for the liver, adrenal cortex, and erythrocytes |
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Term
| Dehydrogenation of glucose 6-phosphate |
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Definition
G6P is made to 6-phosphogluconolactone by G6PD and the conezyme NAD+.
6-PGL is then oxidatively docarboxylated into pentose sugar-phosphate, CO2, and NADPH |
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