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Anaerobic Respiration

Metabolism of Fats & Proteins

Anaerobic Respiration

What happens to pyruvate?

• the fate of the pyruvate molecules depends on whether oxygen is present (aerobic respiration) or not (anaerobic respiration).

• fermentation is the anaerobic reduction of pyruvate to ethanol or lactic acid.

Ethanol Fermentation

• pyruvate is decarboxylated into acetaldehyde, then reduced to ethanol, oxidizing NADH to NAD+

Lactic Acid Fermentation

• pyruvate is reduced to lactic acid, oxidizing NADH to NAD+

Products of FermentationImage from: http://textbookofbacteriology.net/themicrobialworld/Effects.html

Metabolism of Fats & Proteins

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Related Pathways

• proteins, lipids and nucleic acids can also be metabolized for energy by entering into a part of glycolysis or the Krebs cycle

Related PathwaysImage from: http://classes.midlandstech.edu/carterp/Courses/bio225/chap05/ss5.htm

Protein CatabolismImage from: http://academic.brooklyn.cuny.edu/biology/bio4fv/page/3d_prot.htm

• proteins are digested into amino acids

• amino groups are then removed in a process called deamination

Protein Catabolism

• other chemical reactions will convert the remaining part of the amino acids into intermediates of glycolysis or the Krebs cycle

Protein Catabolism

alanine, cysteine, glycine, serine, threonine

pyruvate

asparagine, aspartate oxaloacetate

arginine, glutamate, glutamine, histidine, proline

α-ketoglutarate

isoleucine, methionine, valine succinyl-CoA

leucine, lysine acetyl-CoA

Lipid StructureImage from: http://www.future-of-technology.com/index.php?p=2_7

• most of the fats digested by humans are triglycerides.

Lipid Catabolism

• triglycerides are first digested into glycerol and fatty acids

• glycerol is either converted into glucose through gluconeogenesis or DHAP (then G3P), and enters glycolysis

Lipid Catabolism

• fatty acids are transported to the matrix of the mitochondria and undergo β-oxidation

β-oxidation

• the fatty acid chain is cleaved into 2-carbon acetyl groups, which are converted into acetyl-CoA, which can enter the Krebs cycle

• every cleavage uses one ATP and produces one NADH and one FADH2

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