Biochem Exam 1: Set 3 (TCA Cycle, Electron Transport) Flashcards
If there is a positive change in free energy, what direction will the reaction move?
reverse direction
What are ways to drive an energetically unfavorable reaction (positive delta G)?
add substrate or remove product
couple the reaction with an energetically favorable one
How many high-energy electrons result from one turn of the citric acid cycle?
8
What are sources of Acetyl-CoA?
fatty acids, ketone bodies, pyruvate (from glucose and amino acids), ethanol
What are the outputs of one turn of the TCA cycle?
2 CO2
1 GTP
3 NADH
1 FADH2
What is the final electron acceptor in the electron transport chain?
oxygen
What enzyme catalyzes the conversion from pyruvate to acetyl CoA?
Pyruvate Dehydrogenase Complex
What is the net reaction catalyzed by pyruvate dehydrogenase complex?
pyruvate + CoA + NAD+ –> acety CoA + CO2 + NADH
What are the cofactors for the reaction catalyzed by pyruvate dehydrogenase complex?
thiamine pyrophosphate
lipoic acid, FAD
How many subunits do alpha-keto acid dehydrogenase complexes have?
3 (E1, E2, E3)
Arsenate/Arsenite effect what subunit of PDC and alpha-ketoglutarate dehydrogenase complex?
E2
Vitamin B1 is a component for what subunit of alpha-keto acid dehydrogenase complexes?
E1 (TPP)
What are the regulators of PDC?
\+phosphatase \+Ca2+ \+pyruvate \+NAD+ -ADP -acetyl CoA -NADH
What are the components of TCA cycle…
citrate–>isocitrate–>alpha-ketoglutarate–>succinyl CoA–>succinate–>fumarate–>malate–>oxaloacetate
What are the enzymes of TCA cycle…
citrate synthase, aconitase, isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, succinate thiokinase, succinate dehydrogenase, fumarase, malate dehydrogenase
Which steps in the TCA cycle produce NADH?
isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, malate dehydrogenase
Where is FADH produced in the TCA cycle?
succinate dehydrogenase
Where is GTP produced in the TCA cycle?
succinate thiokinase
Where is CO2 produced in the TCA cycle?
isocitrate dehydrogenase, a-ketoglutarate dehydrogenase
What are the regulators of the TCA cycle?
+ADP
+Ca2+
-NADH
-citrate
What are the key regulatory steps of the TCA cycle?
citrate synthase, isocitrate dehydrogenase (biggest regulatory step), a-ketoglutarate dehydrogenase, malate dehydrogenase
What intermediates in the TCA cycle can be replenished?
oxaloacetate (by pyruvate), a-ketoglutarate (by glutamate), succinyl CoA (by propionyl CoA from odd-chain fatty acid oxidation)
What are the two ways to make ATP?
substrate level phosphorylation, oxidative phosphorylation (electron-transport chain)
How is NAD+ reduced to NADH?
accepts 2 electrons and 1 H+ (a hydride ion)
How is FAD reduced to FADH?
accepts 1 electron and 1 H+
What vitamin is necessary to make NAD/NADH, and what are symptoms from a deficiency in this vitamin?
Niacin (B3)
B3 deficiency = pellagra: dermatitis, dementia, diarrhea
What are the five complexes of the electron transport chain?
- NADH Dehydrogenase
- Succinate-Q reductase
- Cytochrome bc1 complex
- Cytochrome C oxidase
- ATP Synthase
What are the two mobile electron carriers in the inner-mitochondrial membrane?
Coenzyme Q
Cytochrome C
What metals are required in the electron transport chain?
Copper and Iron
What portion of the mitochondria has the highest concentration of protons?
intermembrane space
How many protons are pumped across the membrane by each complex in the ETC?
1 = 4 H+ 2 = 0 H+ 3 = 4 H+ 4 = 2 H+
Which reducing agents are used by complexes 1 and 2 in the ETC?
Complex 1 = NADH
Complex 2 = FADH
How many protons are required to synthesize one ATP
4 H+
3 to turn ATP synthase and 1 to pump ATP out of mitochondria
How does ADP get into the mitochondrial matrix?
ATP-ADP translocase
How do cyanide and CO disrupt ETC?
bind to heme iron in Complex 4 and stop final transfer of electrons to oxygen
If complex 1 is inhibited what happens to ATP production through oxidative phosphorylation?
ATP production is decreased but not halted entirely. Electrons can enter the ETC through complex 2, but the 4 protons transferred by complex 1 do not occur.
How do uncoupling agents effect ATP synthesis?
movement of proton not linked to ATP synthesis, energy is lost to heat (brown fat)
Why does hypoxia lead to acidosis?
NAD+ is regenerated from NADH anaerobically and lactic acid is produced
What are the dangers of aspirin overdose?
Aspirin degradation produces salicylate which is lipid soluble and has a dissociable proton and can act as an uncoupling agent by ferrying protons across the inner mito. membrane
How many ATP are synthesized per oxygen consumed
2.5
How many ATP are produced per glucose molecule?
30-32 (depending on method of NADH transport)
Why are mitochondrial genetic disorders due to mutations in mitochondrial encoded genes?
DNA repair mechanisms aren’t as good in the mitochondria as in the nucleus, and inheritance from mother prevents homozygous recessive disorders from being silent in offspring as a heterozygous genotype
