Metabolism in the cytosol and mitochondria of the skeletal muscle.

The metabolites are grouped in different pathways: the glycogen metabolism pathway, glycolysis, pentose phosphate pathway (PPP) and amino acid metabolism: BCAA: branched-chain amino acid; AAA: aromatic amino acid; PEP: phosphoenol pyruvic acid; MPC: mitochondrial pyruvate carrier; CPT: carnitine palmitoyl transferase; OXPHOS: oxidative phosphorylation. The TCA cycle is the final and universal step before the vast amount of ATP is created at the level of the electron transport system (OXPHOS). Apart from fat and glucose, also proteins can be catabolized to produce precursors of glycolysis and the TCA cycle. Amino acids can feed into the TCA cycle at acetyl CoA, as well as at steps further downstream from acetyl CoA (jagged arrows).