How is pyruvate converted to alanine

   The liver has high oxidative capacity, especially in the peripheral (oxygen-rich) zone I of its acini. It can build up glucose from lactate, which floods in from muscle cells (especially during physical exertion) and make it available to the muscles again (Cori cycle). The liver also produces glutamate (can be converted into urea) and pyruvate (can be used for glucose synthesis) from alanine and ketoglutarate; In the muscle, the reaction runs in the other direction, so excess nitrogen from the muscle (glutamate / alanine) finally passes through the liver into the urine (as urea). The enzyme required in both cases is alanine aminotransferase (ALT), which is considered to be liver-specific
 
   Gluconeogenesis is used for the supply of glucose (~ 200 g / d), especially for the brain; Glycogenolysis is stimulated by adrenaline and glucagon (increased energy requirement), inhibited by insulin (postprandial); glycolysis (EMP pathway) breaks down glucose to pyruvate and forms ATP / NADH. Amino acids, carbohydrates and electrolytes get into the cell from the extracellular space by means of transporters, the synthesis of which can be regulated. The pentose phosphate route carries out nucleotide synthesis and forms reduction equivalents (NADPH / H +). ß-oxidation means fatty acid breakdown. The urea cycle (Krebs-Henseleit) forms urea from nitrogen-containing breakdown products (ammonium, etc.). Transaminations transpose α-amino groups from amino acids to α-keto acids. Ketone bodies are a transportable form of acetyl-CoA (starvation metabolism). Fatty acid synthase enables lipogenesis, the mevalonate pathway enables cholesterol synthesis
 
   In a state of hunger and untreated diabetes mellitus, the liver produces increased (up to 20-fold) ketone bodies (ketosis). ß-Oxy-butyric acid and acetoacetic acid serve primarily as an alternative source of energy for the brain; Acetone is of diagnostic importance. More fatty acids come from the adipose tissue and glucoplastic amino acids from the muscles
 
   > 90% of nitrogen is removed from the body via urea (~ 900 mM N / d). In acidosis, the excretion of ammonium chloride (acidic valences) increases via glutamine / glutamate / ammonium, while bicarbonate is formed at the same time. In alkalosis, urea excretion is accelerated and ammonium excretion is reduced
 
   Cholesterol is mainly excreted in the bile. From this, hepatocytes form primary bile salts (cholate, chenodeoxycholate), which are conjugated with glycine, sulfate, glucuronate or taurine and excreted in the bile ducts. Monovalent bile salts are excreted via the canalicular bile salt exporter (BSEP), bivalent ones via the canalicular pump MRP2, together with other anions. Phosphatidylcholine is transported via the phospholipid exporter, organic cations via the multidrug exporter MDR1. Bile acids are reabsorbed in the ileum (ileal sodium / bile transporter ISBT)