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Anaerobic Pathways (4.4)& Alternatives To Glucose (4.3)

Anaerobic Pathways

What happens to pyruvate?

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

Alcohol Fermentation

Lactate Fermentation

Products of Fermentation

Anaerobic Respiration

• many prokaryotes have electron transport chains on internal membrane systems

• terminal electron acceptor can be O2 (aerobic) or other molecules (anaerobic) such as SO4

2-, NO3-, Fe3+

Alternatives to Glucose

Related Pathways

Related Pathways

• larger carbohydrates, proteins and lipids can also be metabolized for energy by entering into a part of glycolysis or the citric acid cycle

Related Pathways

Protein Catabolism

• 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 citric acid 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 Structure

• 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 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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