Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
20 Cards in this Set
- Front
- Back
|
Name the three most central catabolic pathways of intermediary metabolism.
|
Glycolysis, Kreb’s Cycle, and Oxidative Phosphorylation/electron transport
|
|
|
Name the purpose of Glycolysis
|
conversion of glucose to pyruvate (2 of them per glucose), and then to Acetyl CoA
|
|
|
Name the purpose of Kreb’s Cycle
|
“fixes” oxaloacetate to Acetyl CoA (from glycolysis), producing C6 substrate citrate, which is broken down oxidative to oxaloacetate in 1 turn of cycle.
|
|
|
Name the purpose of Phosphorylation/electron transport
|
Conversion of “reducing equivalents” to H2O (NADH, FADH2, and QH2). FoF1 ATPase converts the “protonmotive force” generated by electron transport into phosphorylation of ADP to produce ATP.
|
|
|
Name the products of Glycolysis
|
2 ATP per glucose, 2 Acetyl CoA, 4 NADH (yielding 10 ATP equivalents)
|
|
|
Name the products of Kreb’s Cycle
|
CoA-SH, 3 NADH(x2 per glucose, yielding 15 ATP), 1 QH2 (x2 per glucose, yielding 3 ATP) 1 GTP (x2 per glucose), 2CO2, and 2H+.
|
|
|
Name the products of Phosphorylation/electron transport
|
NAD+, FAD, coenzyme Q (all oxidized), and ATP; H2O is produced by reduction of ½ O2.
|
|
|
Define “metabolically irreversible”
|
Having a large negative ∆G; highly spontaneous thermodynamically and predisposed almost completely to product formation. Three reactions in glycolysis are metabolically irreversible: those catalyzed by phosphofructosekinase-1, hexokinase, and pyruvate kinase. Constitute key control points for metabolic regulation, specifically by allosteric factors.
|
|
|
Define “near equilibrium”
|
Having a ∆G close to or near zero; flux is approximately equal in both directions. All but three are near equilibrium.
|
|
|
Why should citrate negatively regulate the phosphofructokinase-1 reaction? What is the general term for this phenomenon?
|
Negative regulation of PFK-1 by citrate is an example of negative feedback inhibition of glycolysis by a key Kreb’s Cycle intermediate. If plenty of citrate is present, sufficient acetyl CoA is being produced by glycolysis and the pathway should be inhibited.
|
|
|
Why should Fructose-1,6-bisphosphate stimulate the pyruvate kinase reaction? What is the general term for this phenomenon?
|
Stimulation of pyruvatekinase by fructose-1,6-bisphosphate is an example of feed-forward stimulation. Too much fructose-1,6-bisphosphate indicates that it is accumulating, that the later reaction should occur to a greater extent in order to use the accumulated intermediate.
|
|
|
What is Trios phosphate isomerase (definition, reactants, products)
|
Fructose-1,6-bisphosphate dissociates to form 2 C3 compounds, dihydroxyacetone phosphate and glyceraldehyse 3-phosphate in the aldolase reaction. Since only the later compound can be used in subsequent reactions, the former must be converted into the latter. This reaction is catalyzed by trios phosphate isomerase.
|
|
|
What is aldolase (definition, reactants, products)
|
Catalyzed aldol condensation in the reverse direction, but cleaves fructose-1,6-bisphosphate to form dihydroxyacetone phosphate and glyceraldehydes 3-phosphate in the forward direction (with regard to glycolysis).
|
|
|
Name the coenzyme used by dihydrolipoamide acetyl transferase and explain how it functions fueling the Kreb’s Cycle.
|
Lipoic acid is a lipid-based hydrocarbon that acts as a covalently attached tether between the pyruvate dehydrogenase E2 subunit and the acetyl group. It functions by accepting the ethanol group from the thiamine pyrophosphate group (on the E1 subunit),by forming a thioacetate, and finally by transferring the acetate Coa-SH
|
|
|
Define “proton motive force.” Explain what enzyme uses this phenomenon as the driving energy for ATP synthesis in oxidative phosphorlyation.
|
Oxidative loss of reducing equivilants due to a proton gradient across a membrane.
|
|
|
How does electron transport drive the production of the proton motive force?
|
The electron transport reactions “pump” H+ out of the mitochondrial matrix and build up the [H+] in the inner-membrane space, which drives ATP synthesis by the FoF1 ATPase.
|
|
|
Coenzymes/substrates in the pyruvate dehydrogenase complex shuttles C2 fragments in the following order:
|
Thiamine, pyrophosphate-E1, lipoyl-E2, CoA-SH, citrate
|
|
|
Pyruvate translocase
|
“fuels” the Kreb’s cycle.
|
|
|
The correct order of substrate production in the Kreb’s cycle is
|
succinate, fumarate, malate, oxaloacetate, citrate.
|
|
|
Β-oxidation yields the following:
|
1 FADH2, 1QH2 (indirectly), 2 NADH, 2H+, 1 acetyl CoA and a 2 C unit shorter fatty acid.
|
