Anaerobic Process of Generating Metabolic Energy

The main focus of Chapter 13 is the catabolism of glucose through glycolysis. Related, though lower -priority concepts include the catabolism of other sugars, polysaccharides, glycerol, and formation of lactate and ethanol.

Key points to remember about glycolysis:

> 1. Glycolysis can proceed by mechanisms that are either anaerobic (non-oxidative - little or no oxygen present) or aerobic (oxidative - oxygen present and electron transport and oxidative phosphorylation are occurring).

> 2. Glycolysis produces NADH from NAD+ in Reaction 6 (G3P <=> 1,3BPG). In aerobic glycolysis, NADH is converted to NAD+ by the processes of electron transport and oxidative phosphorylation, which occur in the mitochondria. If oxygen is limiting (such as during heavy exercise), oxidative phosphorylation does not occur and NADH is not converted to NAD+. This could be disastrous if there were no other way to produce NAD+. Under these circumstances, pyruvate is converted to lactate (see reaction), yielding NAD+

> 3. Anaerobic glycolysis is much less efficient than aerobic glycolysis. Anaerobic glycolysis produces only 2 net ATPs per molecule of glucose, whereas aerobic glycolysis produces 38 molecules of ATP per molecule of glucose.

> 4. Regulatory mechanisms for glycolysis include

> > 1. Allosteric regulation

> > 2. Hormonal control (via the kinase cascade)

> > 3. Substrate level control

> > 4. Covalent modification (phosphorylation via the kinase cascade)

> 5. Key regulatory enzymes for glycolysis include

> > 1. Hexokinase (substrate-level regulation by glucose-6-phosphate)

> > 2. Phosphofructokinase (allosteric regulation by F2,6BP, AMP, ADP, ATP, citrate)

> > 3. Pyruvate kinase (allosteric regulation by ATP, acetyl-CoA, D-fructose-1,6-bisphosphate and covalent modification - namely, phosphorylation)

See also: Oxidative Phosphorylation (from Chapter 15), Regulation of Glycolysis, Fructose-2,6-Bisphosphate Regulation (from Chapter 16), Reactions/Energies of Glycolysis, Lactic Acid fermentation, Pyruvate Decarboxylase, Alcohol Dehydrogenase, Alcoholic Fermentation, Aerobic vs. Anaerobic Glycolysis