Flashcards in Topic 11 - Aerobic Metabolism vs. Anaerobic Metabolism, PDH (Multi-enzyme complexes) Deck (17):
Is Glycolysis considered anaerobic or aerobic process?
It is an anaerobic process that is used by both anaerobic and aerobic organisms. The anaerobic catabolism of carbohydrates goes no further than glycolysis + fermentation reactions. Aerobic catabolism begins with glycolysis and continues with the aerobic phase until the carbons of glucose are fully oxidized to CO2, using Oxygen as the ultimate electron acceptor.
Where does Glycolysis occur? Where does the aerobic phase occur?
Glycolysis (anaerobic phase of catabolism) occurs in the cytoplasm of all organisms. Aerobic phase begins in the mitochondrial matrix and continues in the mitochondrial IM, so there must be eventual transport of pyruvate (or its breakdown products) from the cytosol to the mitochondria.
What does further catabolism of pyruvate accomplish (aerobic or anaerobic)?
NAD+ that was reduced to NADH in GAPDH reaction of Glycolysis needs to be regenerated.
What are the 2 possible anaerobic catabolic pathways of pyruvate? What is the aerobic catabolic pathway of pyruvate?
Anaerobic: 1) Homolactic fermentation & 2) Alcoholic fermentation.
Aerobic: Citric Acid Cycle/TCA Cycle.
The pathway utilized depends on the organism and/or tissue.
How does the energy released by either anaerobic metabolism of glucose or aerobic metabolism (complete oxidation) differ?
Glycolysis only releases a small fraction of the energy of glucose! This limits the efficiency of anaerobic organisms.
Anaerobic metabolism of glucose: Releases ΔGo' = -135 kJ/mol.
Aerobic metabolism of glucose: Releases ΔGo' = -2,840 kJ/mol (much more efficient!).
What molecular weight do the porin channels of the mitochondrial OM allow?
Less than 10,000 MW.
What is the mitochondrial IM permeable to?
O2, CO2, H2O
What is a multi-enzyme complex? What are its advantages?
A multi-enzyme complex is a noncovalent but stable physical aggregation of enzymes catalyzing successive reactions of the pathway.
1) The enzyme complex channels intermediates directly to each of the enzymes, catalyzing successive reactions of the pathway.
-It eliminates reliance on diffusion so that reaction rate is not limited by diffusion rates or on random collisions.
-The product of one reaction is committed to this pathway - It is passed directly to the next active site and therefore cannot be diverted to enzymes of competing pathways.
2) The enzyme complex can be coordinately regulated - Inhibition at any reaction will result in inhibition of all enzymes catalyzing earlier reactions of the complex.
What is the Pyruvate Dehydrogenase (PDH) Multienzyme Complex also known as?
The bridge between Glycolysis (anaerobic) and the TCA Cycle (aerobic).
Net reaction of PDH complex: ΔG = -30 kJ/mol.
Pyruvate + Coenzyme A-SH + NAD+ --> Acetyl-SCoA + CO2 + NADH
What 3 enzymes make up the PDH complex?
1. E1 = Pyruvate Dehydrogenase (PDH)
2. E2 = DiHydroLipoyl TransAcetylase (DHL TA)
3. E3 = DiHydroLipoyl Dehydrogenase (DHL DH)
What are the cofactors for each enzyme?
1. E1 = Pyruvate Dehydrogenase (PDH) = Thiamine PyroPhosphate (TPP).
2. E2 = DiHydroLipoyl TransAcetylase (DHL TA) = Lipoamide arm.
3. E3 = DiHydroLipoyl Dehydrogenase (DHL DH) = Flavin Adenine Dinucleotide (FAD).
What is the structure of Thiamine PyroPhosphate (TPP) and its function?
What is the structure of the Lipoamide arm and its function?
What is the structure of Flavin Adenine Dinucleotide (FAD) and its function?
What is the structure of Coenzyme A and its function?
What is the structure of NAD and its function?