Tag: Fatty acid transport

Approximately 95% of dietary fat is absorbed in the small intestine, but this process requires a sophisticated, multi-stage transport mechanism due to the water-insoluble nature of lipids. This complex system ensures that essential fatty acids and monoglycerides can be efficiently absorbed into the body despite the watery environment of the digestive tract.

Not all nutrients absorbed from the small intestine travel to the liver in the same manner; the answer to whether fatty acids are transported to the liver via the hepatic portal vein is not a simple 'yes' or 'no' but depends crucially on their carbon chain length. Short- and medium-chain fatty acids are indeed sent directly to the liver via this route, but longer chains take a completely different path.

Fatty acids are a major source of energy for the body, especially during fasting or exercise, supplying over twice the energy per unit mass compared to carbohydrates. This energy is harnessed through a process called beta-oxidation, which occurs inside the mitochondria, requiring a specialized system for getting fatty acids through the mitochondrial membrane.

While often mistakenly called a vitamin, L-carnitine is the critical compound that transports long-chain fatty acids into the mitochondria, the cell's powerhouse, for energy production. This essential process, known as the carnitine shuttle, ensures that the body can effectively burn fat for fuel, especially during periods of high energy demand like fasting or intense exercise.

The human brain is an astonishing organ, with nearly 60% of its dry weight composed of lipids, making fatty acids crucial for its structure and function. This naturally leads to the complex question of how does the brain get fatty acids, especially considering the highly restrictive nature of the blood-brain barrier.

Over 90% of circulating fatty acids are bound to the protein serum albumin, which is essential because fatty acids are hydrophobic and insoluble in blood plasma. So, what transports free fatty acids throughout the body, across cell membranes, and into the mitochondria to be used for energy?