Describe the process of lipid metabolism, starting from digestion in the mouth to absorption and transportation in the body. Include key enzymes, organs involved, and the role of bile in fat emulsification.
The correct answer and explanation is :
Lipid metabolism begins in the mouth and continues through various organs and enzymes to facilitate the digestion, absorption, and transportation of fats in the body.
- Digestion in the Mouth:
Digestion of lipids starts in the mouth, where the enzyme lingual lipase, secreted by glands in the tongue, begins the breakdown of triglycerides (fats). However, fat digestion is minimal here because the enzyme only acts at a low pH. - Stomach:
After swallowing, the food moves to the stomach. In the stomach, gastric lipase further breaks down triglycerides into diglycerides and free fatty acids. The acidic environment in the stomach also aids in fat digestion, but again, fat digestion remains limited. - Small Intestine:
The majority of lipid digestion occurs in the small intestine. Here, bile, secreted by the liver and stored in the gallbladder, plays a critical role. Bile emulsifies large fat droplets into smaller ones, increasing the surface area for the enzyme pancreatic lipase to act. Pancreatic lipase is released from the pancreas and breaks down triglycerides into monoglycerides and free fatty acids. - Absorption:
The products of lipid digestion (monoglycerides and fatty acids) combine with bile salts to form micelles, which facilitate the absorption of lipids into the enterocytes (intestinal cells) of the small intestine. Inside the enterocytes, monoglycerides and fatty acids are re-esterified into triglycerides. - Transportation:
These newly formed triglycerides are packaged into chylomicrons (lipoprotein particles) that enter the lymphatic system and are eventually transported to the bloodstream. The chylomicrons transport lipids to various tissues for energy production, storage, or other functions.
Bile’s role in emulsification is vital for the efficient digestion of fats, as it transforms large lipid droplets into smaller ones, allowing digestive enzymes to access and break them down.
Here is an illustration of lipid metabolism, showing the key processes involved in digestion, absorption, and transportation of fats in the body. It highlights the enzymes, organs, and the role of bile in fat emulsification.