Chapter 10 - Carbohydrate Metabolism II: Aerobic Respiration Flashcards
Pyruvate Dehydrogenase Complex
multienzyme complex, pyruvate enters mitochondrial matrix via active transport and is oxidized and decarboxylated by the PDC
What happens when alcohol is consumed in moderate amounts?
alcohol dehydrogenase and acetaldehyde dehydrogenase convert it to acetyl-CoA; accompanied by NADH buildup which inhibits TCA, so acetyl-CoA formed through this process is used primarily to synthesize fatty acids
What is the rate-limiting enzyme of the citric acid cycle?
Isocitrate dehydrogenase. Isocitrate is oxidized to oxalosuccinate via the enzyme. Then gets decarboxylated to produce alpha-ketoglutarate and CO2, first of two carbons from cycle are lost, first NADH produced from intermediates in the cycle
What is the difference between a synthase and synthetase?
Synthases form new covalent bonds without needing significant energy. Synthetases create new covalent bonds with energy input.
What type of enzymes are dehydrogenases?
Oxidoreductase. Transfer a hydride (H-) to an e- acceptor, like NAD+ or FAD
Which step of TCA does not take place in the mitochondrial matrix?
step 6, fumarate formation; catalyzed by succinate dehydrogenase, a flavoprotein, bc it’s covalently bonded to FAD
What is the mnemonic for substrates of TCA?
Please, Can I Keep Selling Stimulants For Money, Officer? Pyruvate, Citrate, Isocitrate, a-Ketoglutarate, Succinyl-CoA, Succinate, Fumarate, Malate, Oxaloacetate
What is the net equation for the pyruvate dehydrogenase complex?
Pyruvate + CoA-SH + NAD+ –> acetyl-CoA + NADH + CO2 + H+
What are the products of the citric acid cycle?
2 CO2, CoA-SH, 3 NADH, 3 H+, FADH2, and GTP
How much ATP is produced during TCA?
4 NADH –> 10 ATP (2.5/NADH)
1 FADH2 –> 1.5 ATP
1 GTP –> 1 ATP
Total: 12.5 ATP per pyruvate = 25 ATP per glucose
What are the 3 control points of TCA?
3 essential checkpoints: citrate synthase, isocitrate dehydrogenase, and a-Ketoglutarate dehydrogenase complex
Why are coenzyme Q and cytochrome C important for the ETC?
Technically they’re not part of the complexes. But they both are able to move freely in the inner mitochondrial membrane, this degree of mobility allows these carriers to transfer electrons by physically interacting with the next component of the transport chain
Q Cycle
shuttles electrons, increases the gradient of the proton-motive force across the inner mitochondrial matrix
Glycerol-3-phosphate shuttle
Cytosol contains one isoform of G3P dehydrogenase, that oxidizes cytosolic NADH to NAD+ while forming G3P from DHAP; outer face of inner mitochondrial membrane has another isoform of G3P dehydrogenase that’s FAD-dependent, gets reduced to FADH2, transfers its e- to ETC via complex II (generates 1.5 ATP for every cytosolic NADH)
Malate-aspartate shuttle
cytosolic oxaloacetate is reduced to malate so it can enter the inner mitochondrial matrix via cytosolic malate dehydrogenase, NADH gets [o], then once inside the matrix the rxn reverses to get NADH again, passes along e- to Complex I (2.5 ATP per NADH)
