The liver, a large organ in the upper right abdomen, acts as a central processing unit for the body’s internal environment. It performs a wide array of biochemical reactions to maintain overall health. The liver manages substances we consume and those the body naturally produces, supporting energy production, nutrient distribution, and the removal of harmful compounds.
Handling Sugars and Energy
The liver is a primary regulator of blood sugar levels, ensuring a steady supply of energy for the body’s cells. When glucose enters the liver after a meal, the liver converts it into glycogen for storage through a process called glycogenesis. This stored glycogen acts as an energy reserve, ready for use when glucose levels in the bloodstream decrease.
During periods between meals or fasting, when blood glucose levels fall, the liver initiates glycogenolysis, breaking down stored glycogen into glucose. This glucose is then released into the bloodstream to restore normal levels and provide fuel for other tissues. If fasting continues and glycogen stores are depleted, the liver begins gluconeogenesis, synthesizing new glucose from non-carbohydrate sources like lactate and glycerol. These processes, regulated by hormones like insulin and glucagon, ensure the body has access to the glucose it needs for proper function.
Processing Fats and Lipids
The liver plays a significant role in fat metabolism, handling their synthesis, breakdown, and transport throughout the body. It manufactures fatty acids and cholesterol, components for cell membranes and hormone production. Since fats are not water-soluble, the liver packages them into special particles called lipoproteins for transport in the bloodstream.
Very-low-density lipoprotein (VLDL) is synthesized in the liver to carry triglycerides from the liver to peripheral tissues for energy or storage. As VLDL loses triglycerides, it transforms into intermediate-density lipoprotein (IDL), which can be taken up by the liver or further converted into low-density lipoprotein (LDL). LDL is rich in cholesterol and delivers it to cells throughout the body, while high-density lipoprotein (HDL) performs “reverse cholesterol transport,” returning excess cholesterol from tissues back to the liver for excretion. The liver manages these lipoprotein dynamics to maintain lipid balance and support cellular functions.
Managing Proteins and Amino Acids
The liver is central to the metabolism of proteins and amino acids. It synthesizes most plasma proteins, including albumin, which maintains fluid balance, and various clotting factors. The liver can also convert one type of amino acid into another to meet the body’s protein needs.
When amino acids are broken down, ammonia is produced. The liver has a specialized pathway, the urea cycle, to convert this harmful ammonia into urea. This process occurs partly in the mitochondria and partly in the cytoplasm of liver cells, producing urea, a much less toxic compound. Urea is then transported to the kidneys for excretion in the urine, preventing ammonia buildup that could be damaging to the central nervous system.
Neutralizing Toxins and Medicines
The liver functions as the body’s primary detoxification organ, processing and neutralizing a wide range of harmful substances. This includes drugs, alcohol, environmental pollutants, and metabolic waste products. The detoxification process occurs in two main phases.
Phase I reactions involve enzymes that modify toxins by adding reactive or polar groups. While these modifications can make substances less harmful, some intermediate products may still pose a risk. Phase II reactions then attach larger, water-soluble molecules like glutathione, sulfate, or glycine to these modified compounds. This conjugation makes the substances more water-soluble and easier for the body to excrete through bile or urine.