Alternative Metabolic Pathways

Carbohydrates are the first nutrient most organisms catabolise for energy, however, living things must metabolize other energy-rich nutrients to obtain energy in times of starvation

Protein Catabolism

– first digested into amino acids

– amino groups are removed (deamination; amino group à ammonia [NH₃])

– remaining portion of amino acid converted into various components of glycolysis or the Krebs cycle

– the type of amino acid determines the point of entry into these metabolic pathways,

– For example, leucine is converted into acetyl-CoA, alanine is converted into pyruvate

Lipid Catabolism

– first triglycerides are digested into glycerol and fatty acids

– glycerol may be converted into glucose (glucaoneogenesis), or it may be changed into DHAP or G3P à fed into glycolysis

– fatty acids transported to mitochondria (b-oxidation)

– b-oxidation is the removal  of two-carbon acetyl groups, starting at the carboxyl end

– acetyl groups combine with coenzyme A to form acetyl-CoA à enter the Krebs cycle

Ethanol Fermentation

– allows NAD+ to be recycled and glycolysis to continue

Lactic Acid Fermentation

– allows NAD+ to be recycled and glycolysis to continue

– lactate in muscle tissue causes stiffness, soreness and fatigue

– lactate is oxidized back to pyruvate, which then goes through the Krebs cycle when vigorous activity ceases

William Anderson (Schoolworkhelper Editorial Team)

William completed his Bachelor of Science and Master of Arts in 2013. He current serves as a lecturer, tutor and freelance writer. In his spare time, he enjoys reading, walking his dog and parasailing. Article last reviewed: 2022 | St. Rosemary Institution © 2010-2024 | Creative Commons 4.0

See Full Bio