Redox reactions release energyRedox reaction (oxidation-reduction)

Na + Cl Na+ + Cl-

oxidation

reduction

Xe- + Y X + Ye-

oxidation

reduction

Not all redox reactions involve the complete transfer of electrons:

NAD+ and NADP+ are electron shuttles

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

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