Question

Fermentation, Lipid Catabolism and Protein Catabolism are all types of alternatives to carbohydrate catabolism. Describe the specific details of these three alternatives in the context of the stages of cellular respiration. In other words, how and where is the ATP produced?

Answer 1

Cellular Respiration

Explanation:

• Glycerol is changed into one of the intermediate product of glycolysis, so enters the cell respiration pathway
• Unsaturated fats are changed in a progression of responses called beta-oxidation into acetyl CoA molecules, which enter cell digestion at the Kreb's Cycle
• A large portion of the ATP produced by cellular respiration is made by oxidative phosphorylation
• 38 ATP atoms can be made per oxidized glucose particle during cellular respiration (2 from glycolysis, 2 from the Krebs cycle, and around 34 from the electron transport system)

Answer 2

Cellular respiration

Explanation:

Fermentation

• Any energy yielding metabolic reaction in which final electron acceptor is an internal organic molecule(generally an intermediate of metabolic reaction)
• Fermentation is exclusively operated in absence of oxygen
• There are two types of fermentation:
• Lactic acid fermentation: Pyruvate is the final electron acceptor and converted in lactate, reaction is catalysed by lactate dehydrogenase
• Alcoholic fermentation: Final electron acceptor is acetaldehyde which is converted in ethanol

Lipid Catabolism

• In catabolism of lipids, Glycerol is be phosphorylated to glycerol-3-phosphate and easily converted to glyceraldehyde 3-phosphate, which continues through glycolysis
• The released fatty acids are catabolized in a process called β-oxidation( activation of fatty acid occurs in cytoplasm whereas transportation of fatty acid and proper β-oxidation occurs in matrix of mitochondria), fatty acids are oxidized to yield FADH2, NADH and acyl CoA
• 1 β-oxidation cycle provides 1 FADH2, 1 NADH and 1 acetyl CoA

Protein Catabolism

• Proteins are degraded through the concerted action of a variety of microbial protease enzymes, extracellular proteases cut proteins internally at specific amino acid sequences, breaking them down into smaller peptides that can then be taken up by cells
• After extracellular protease degradation and uptake of peptides in the cell, the peptides can then be broken down further into individual amino acids by additional intracellular proteases, and each amino acid can be enzymatically deaminated to remove the amino group
• The remaining molecules can then enter the transition reaction or the Krebs cycle
• Kreb cycle occurs in the matrix of mitochondria where 1 molecule of Acetyl CoA gives 12 ATP