Aerobic Respiration Flashcards
Where does the CAC/KC take place & what is the main function of this pathway?
Mitochondria
Functions to oxidize acetyl coA to CO2 & H2O
What are the pyruvate dehydrogenase complex enzymes needed to catalyze acetyl-CoA from pyruvate, & what are their functions ?
- PDH: oxidizes pyruvate, yields CO2
- Dihydrolipoly transacetylase: oxidizes 2 C molecules bonded to thiamine pyrophosphate & transfers them to lipoic acid; also catalyzes CoA-SH to acteyl-CoA
- D. dehydrogenase: FAD reoxidizes lipoic acid (for future use) & reduced to FADH2
What other pathways are capable of forming acetyl-CoA?
- Fatty acid oxidation (beta-oxidation)
- Amino acid catabolism
- Ketone bodies
- Alcohol
Where in the mitochondria does the CAC specifically take place ?
Mitochondrial matrix
What rxns take place in the CAC?
- Acetyl-CoA & oxaloacetate undergo condensation to form citryl-CoA—-> hydrolysis of citryl yields citrate & CoA-SH
- Citrate is isomerized to isocitrate
- Isocitrate oxidized to oxalosuccinate (via isocitrate dehydrogenase: rate limiting step of CAC)—>oxalosuccinate decarboxylated to a-ketoglutarate & CO2
- a-ketoglutarate & CoA-SH form succinyl CoA & CO2
- Hydrolysis of thioester bond on succinyl CoA yields succinate & CoA-SH (coupled yo phosphorylation of GDP to GTP)
- Succinate oxidized to fumarate & FAD reduced to FADH2 in the inner mitochondrial membrane
- Fumarase catalyzes hydrolysis of fumarate & forms malate (L-malate)
- Malate dehydrogenase catalyzes oxidation of malate to oxaloacetate
What are the 3 essential checkpoints that regulate the CAC from within ?
- Citric synthase: ATP & NADH function as allosteric inhibitors
- Isocitrate dehydrogenase: Inhibited by ATP & NADH
- a-ketoglutarate dehydrogenase complex: reaction products of succinyl CoA, ATP, & NADH serve as inhibitory factors
What are the final 2 steps of aerobic respiration ?
ETC & generation of ATP via ADP phosphorylation
The transfer of electrons from NADH to coenzyme Q is catalyzed where ?
Complex I
1. NADH—>FMN—->NAD+ & FMNH2—>CoQ (ubiquinone)—–>CoQH2
What is the main difference between Complex I & II ?
CI receives e- from NADH while C2 receives e- from succinate
- No H+ pumping occurs in C2
- C2: succinate—>FAD & FADH2—> CoQ—-> fumarate & CoQH2
What is the main function of complex III ?
To facilitate transfer of e- from CoQH2 to cytochrome c
*Q cycle : 2 e- transferred from ubiquinol (intermembrane space) to ubiquinone (near mitochondrial matrix)
Complex IV facilitates the transfer of e- from cytochrome c to what final e- acceptor ?
O2
What happens when H+ increases in the intermembrane space ?
pH drops & voltage difference between intermembrane space & matrix increases (create electrochemical gradient)
NADH formed via glycolysis cannot directly cross into the mitochondrial matrix. What shuttle mechanisms aid in transferring the e- transporters through the membrane?
- Glycerol-3-phosphate shuttle
- Malate-aspartate shuttle
What is the F0 portion of ATP synthase & what is its function ?
F0 is the part of ATP synthase that spans the membrane, & it functions as an ion channel (chemiosmotic coupling occurs simultaneously to all chemical energy of gradient to be harnessed for ADP->ATP)
*F1 portion: phosphorylates ADP to ATP
Chemiosmotic coupling describes a direct relationship between what ?
proton gradient & ATP synthesis
*Conformational coupling says its indirect
