Aerobic Catabolism Flashcards
(43 cards)
Where does aerobic catabolism take place?
mitochondria
How does pyruvate become acetyl-coA?
-catalyzed by the pyruvate dehydrogenase complex, in the mitochondria
-large, highly regulated multi-enzyme complex
-OXIDATIVE DECARBOXYLATION
What are the 3 subunits of the PDH complex?
E1- pyruvate dehydrogenase
E2- dihydrolipoyl transacetylase
E3- dihydrolipoyl dehydrogenase
How is acetyl co-A oxidized? GENERAL
-requires oxygen
-releases acetyl carbons as CO2
-generates lots of ATP
What are the two phases of oxidation of acetyl-CoA?
-Krebs cycle: releases CO2 and passes electrons to NAD+ and FAD to generate NADH and FADH2
-Electron transfer and oxidative phosphorylation: passes electrons from NADH and FADH2 to oxygen, uses energy to generate ATP
What is the function of the Krebs cycle in aerobic respiration?
-oxidation of the acetyl group of acetyl-CoA
-the acetyl group of acetyl-CoA is oxidized to CO2
– results in reduction of NAD+ to NADH and FAD to FADH2
–these are fed into the electron transfer chain provide energy for ATP synthesis
How is acetyl-CoA made?
-low concentration
-produced from:
–carbohydrate degradation via glucose and glycolysis (plus PDH reaction)
–triglyceride degradation via fatty acids and B-oxidation
–protein degradation (some amino acids)
What are the 8 steps of glycolysis? GENERAL
- Citrate synthase
- Aconitase
- Isocitrate dehydrogenase
- a-ketoglutarate dehydrogenase complex
- succinyl-CoA synthetase
- Succinate dehydrogenase
- Fumarase
- Malate dehydrogenase
What type of pathway is the Krebs cycle?
Amphibolic, involved In both catabolic and anabolic pathways:
Catabolic- aerobic respiration
Anabolic- intermediates for fatty acid and amino acid synthesis, gluconeogensis
What is a competitive inhibitor of succinate dehydrogenase?
malonate
What is gifblaar?
-South African plant contains fluroracetate, which can be metabolized to flurocitrate in the mitochondria
-potent competitive inhibitor of aconite
Give an overview of acetyl-CoA oxidation.
-electrons from reduced co-enzymes are passed through the electron transfer chain
-each passes electrons to the next member of the chain, which becomes reduced as the donor becomes oxidized
-the energy released is used to pump protons across the inner membrane
-the proton gradient drives ATP synthesis
-source of reduced co-enzymes mostly Krebs, some from cytoplasm
Where does oxidative phosphorylation occur?
mitochondria
What are the key points of the mitochondria?
-outer membrane freely permeable to small molecules
-inner membrane permeable
-Krebs cycle occurs in the matrix (except step 6)
-electron transfer and oxidative phosphorylation in the inner membrane
What are the two phases of oxidative phosphorylation?
-electron transfer reactions
– electrons passed from NADH and FADH2 to oxygen- generates a proton gradient
-proton gradient used to drive ATP synthesis
How do electron transfer reactions in the Mitochondria occur?
-electrons are funneled to universal electron acceptors (NAD+->NADH etc.)
-electrons pass through a series of membrane-bound electron carriers
-oxygen is the final electron acceptor
What are the 3 electron acceptors in the electron transfer chain?
-Ubiquinone (coenzyme Q/Q)
-Cytochromes
-Iron-sulfur proteins
Explain ubiquinone.
-hydrophobic, stays buried in the mitochondrial membrane
-accepts one e- at a time
Explain cytochromes.
Three types in mitochondria:
-A
-B
-C
tightly or covalently bound heme group (prosthetic group)
What is a heme?
-contain porphyrin ring
–4 5-carbon rings, containing nitrogen with a central Fe atom to accept and give up electrons
Explain Iron-sulfur proteins.
-contain iron as iron-sulfur centers
-various arrangements of cys-S, inorganic S, and Fe
What is the order of electron carriers?
NADH
Q
Cyt b
Cyt C1
Cyt C
Cyt A
Cyt A3
O2
What are electron carrier inhibitors?
Rotenone: backs up at Q
Antimycin A: backs up at Cyt C1
CN- or CO: backs up at O2
What are the carriers function in multienzyme complexes? (4 complexes)
1: NADH to Q
2: Succinate to Q
3: Q to Cyt C
4: Cyt C to O2
