Cellular Respiration: Harvesting Chemical EnergyCellular respiration – catabolic energy yielding pathway in which oxygen and organic fuels are consumed and ATP is producedSUMMARY:
Organic + Oxygen Carbon + Water + EnergyCompounds
Dioxide
C6H12O6 + 6 O2 6 CO2 + 6 H2O + Energy
C6H12O6 + 6 O2 6 CO2 + 6 H2O
oxidation
reduction
*By oxidizing glucose, energy is taken out of “storage” and made available for ATP synthesis
NAD+ and NADP+ are electron shuttles
Cellular Respiration: an overview
3 metabolic stages:
*glycolysis *Krebs cycle
*electron transport chain and oxidative phosphorylation
*Substrate-level phosphorylation
*Oxidative phosphorylation
Metabolic Disequilibrium
*Multi-step open system
Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
Glycolysis: Energy Investment Phase
1) Glucose is phosphorylated
2) G-6-P is rearranged
3) Addition of another phosphate group
5) Conversion b/w the 2 3-carbon sugars
4) Cleavage into 2 3-carbon sugars
6) Two components: *electron transfer *Phosphate group addition
Glycolysis: Energy Payoff Phase
7) ATP production
8) Rearrangement of phosphate group
9) Loss of water
10) ATP production
aerobicanaerobic
The presence or absence of O2 dictates the fate of pyruvate
The Krebs cycle: energy-yielding oxidationThe junction b/w glycolysis and the Krebs cycle:
Multienzyme complex:
1) Removal of CO2 2) Electron transfer *pyruvate dehydrogenase 3) Addition of CoA
The Krebs cycle: energy-yielding oxidation
1) Addition of 2 Carbons Citrate
synthase 2)
Isomerization Aconitase
3) *Loss of CO2 *electron transfer
Isocitrate dehydrogenase
4) *Loss of CO2 *electron
transfer -ketoglutarate
dehydrogenase5) substrate-level
phosphorylation Succinyl CoA-synthetase
6) electron transfer Succinate
dehydrogenase
7) Rearrangement
of bonds Fumarase
8) electron transfer Malate dehydrogenase
Electron transport and ATP synthesis
*Multi-step open system
Generation and maintenance of an H+ gradient*Exergonic flow of e-, pumps H+ across the membrane*chemiosmosis
high energy electrons
*How does the mitochondrion couple electron transport and ATP synthesis?
ATP synthase
Fermentation enables cell to produce ATP w/o O2
aerobicanaerobic
*Fermentation generates ATP by substrate-level phosphorylation