Biochemistry of Lipid Metabolism

The process of breaking down fats into smaller molecules that can be absorbed by the body.

An enzyme secreted by the tongue that begins the digestion of fats, especially in infants.

An enzyme secreted by the stomach that continues the digestion of fats.

The process of breaking down large fat globules into smaller droplets, increasing their surface area for digestion.

The primary storage form of energy in the body, composed of three fatty acids linked to glycerol.

The main structural component of cell membranes, composed of a phosphate head and two fatty acid tails.

A type of lipid that serves as a precursor for many hormones, and helps regulate cholesterol levels.

A type of lipid that acts as a surfactant, helping to reduce surface tension in the lungs, allowing for easier breathing.

Bile salts are synthesized in the liver and stored in the gallbladder. They are derivatives of cholesterol, consisting of a sterol ring, a side chain, and either glycine or taurine. They exist as sodium and potassium salts of glycocholic and taurocholic acid.

Bile salts play a crucial role in the digestion of fats in the small intestine. They act as emulsifying agents, breaking down large fat globules into smaller droplets, increasing their surface area for lipase action.

The enterohepatic circulation is a continuous cycle where bile salts are reabsorbed from the small intestine, transported back to the liver, and then secreted back into the bile. This process conserves bile salts and ensures efficient fat digestion.

The small intestine is the primary site for the digestion of fats. Pancreatic lipase, an enzyme secreted by the pancreas, and bile salts work together to efficiently break down fats into smaller molecules.

The secretion of pancreatic juice, containing digestive enzymes and bicarbonate, into the small intestine is triggered by various factors, including the presence of gastric acid and protein-rich content in the duodenum.

Secretin is a hormone released by the intestinal mucosa in response to acidic chyme entering the duodenum. It primarily stimulates the secretion of bicarbonate-rich fluid by the pancreas, helping to neutralize the acidic chyme.

Cholecystokinin (CCK) is a hormone released by the small intestine in response to fats and proteins. It stimulates the contraction of the gallbladder, releasing bile into the duodenum, and also promotes the release of pancreatic enzymes, assisting in fat digestion.

Pancreatic juice contains vital enzymes that break down various components of food, including:

• Pancreatic lipase: Digests triglycerides (fats).
• Phospholipases: Breaks down phospholipids.
• Cholesterol esterase: Breaks down cholesterol esters.

The process of breaking down dietary fat (triglycerides, TG) into smaller molecules that can be absorbed by the body.

Special fats that help dissolve and transport dietary fat through the watery environment of the intestines.

A type of lipoprotein (fat package) that's made in the intestines and carries dietary fat to the rest of the body.

Specialized enzymes that help break down dietary fat, especially cholesterol esters.

The process of breaking down fat molecules into smaller pieces, using water.

The process of breaking down triglycerides (fats) in chylomicrons by lipoprotein lipase, an enzyme found in capillary endothelial cells.

The process where chylomicrons, carrying absorbed triglycerides, enter cells after interacting with a cell receptor.

A condition where lipids are not properly absorbed from the digestive tract, resulting in fat loss in the feces.

A condition characterized by inflammation of the small intestine, affecting lipid absorption.

A digestive enzyme found in capillary endothelial cells; crucial in breaking down triglycerides within chylomicrons, allowing fatty acids to enter cells.

Proteins that associate with lipids in chylomicrons, helping them form a stable structure and interact with other cells.

The process by which chylomicrons are formed and released into the lymph system by intestinal cells.

The initial, smaller form of chylomicrons that are released from intestinal cells, before they become "mature".

The process by which chylomicrons acquire additional proteins, particularly from HDL, becoming fully functional for lipid transport.

A type of hyperlipemia caused by the presence of high levels of chylomicrons in the blood shortly after a meal containing fats.

The highest concentration of lipids (especially triacylglycerols) found in the blood, typically occurring 4-6 hours after a meal containing fats.

The process by which chylomicrons are broken down, releasing their lipids into various tissues.

A type of lipid that acts as a surfactant in the lungs, helping to reduce surface tension and allow for easier breathing.

Enzymes that break down dietary fats, specifically triglycerides, into smaller molecules.

Lipoprotein lipase is an enzyme that breaks down triglycerides in chylomicrons, releasing free fatty acids into surrounding tissues. This process mainly occurs in adipose tissue and muscle.

The continuous recycling of bile salts between the liver, gallbladder, small intestine, and back to the liver.

Bile salts are synthesized in the liver and stored in the gallbladder. They are derivatives of cholesterol, consisting of a sterol ring, a side chain, and either glycine or taurine. They exist as sodium and potassium salts of glycocholic and taurocholic acid.

The breakdown of triglycerides into glycerol and fatty acids, facilitated by pancreatic lipase.

The process where long-chain fatty acids, cholesterol, and β-acyl glycerol form mixed micelles with bile salts, allowing their absorption into the intestinal cells.

Chylomicrons are tiny fat packages made in the intestines that carry absorbed dietary fat through the lymphatic system and into the bloodstream.

Lipoprotein lipase (LPL) is an enzyme located in capillary endothelial cells that breaks down triglycerides within chylomicrons, releasing fatty acids into surrounding tissues.

When chylomicrons enter cells, their triglycerides are broken down by LPL, releasing fatty acids that can be used for energy or stored in the body.

Lipid malabsorption (Steatorrhea) is a condition where lipids are not properly absorbed from the digestive tract, leading to fat loss in the feces. This can be caused by conditions like pancreatic insufficiency, cystic fibrosis, celiac disease, or bowel issues.

Nascent chylomicrons are newly formed chylomicrons that are secreted by the intestinal cells into the lymphatic system. They are smaller and less mature than mature chylomicrons.

Chylomicrons mature as they pick up additional proteins, primarily from HDL (high-density lipoprotein). This process happens in both the lymph and the blood.

Alimentary hyperlipemia is a temporary increase in blood lipid levels, especially triacylglycerols, that happens shortly after a meal containing fat. It is caused by the release of chylomicrons into the blood.

The peak of alimentary hyperlipemia occurs 4-6 hours after a fatty meal. This is when the blood contains the highest concentration of chylomicrons.

The major apolipoprotein associated with chylomicrons is apoB-48. ApoB-48 helps in the assembly and secretion of chylomicrons from intestinal cells.

Chylomicrons are broken down by an enzyme called lipoprotein lipase, which is found on the surface of blood vessels. This process releases fatty acids and glycerol, which can be used for energy or stored in tissues.

The presence of chylomicrons in the blood can interfere with biochemical studies of blood serum. This is because they can cause turbidity (cloudiness) in the serum, making it difficult to analyze.

The process of breaking down large fat droplets into smaller ones, increasing their surface area for digestion by enzymes.

These are tiny clusters of lipids formed in the small intestine. They have a hydrophobic core (fats) and a hydrophilic outer layer (bile salts). They help transport lipids to the intestinal cells.

Bile salts, synthesized in the liver and stored in the gallbladder, are crucial for fat digestion. They act as emulsifiers, breaking down large fat globules into smaller droplets, increasing their surface area.

The major apolipoprotein associated with chylomicrons, playing a crucial role in their assembly and secretion from intestinal cells. It's a shorter version of apolipoprotein B, synthesized specifically for chylomicrons.

The process by which chylomicrons are broken down, releasing their lipids into various tissues. It's crucial for delivering fats to cells for energy or storage.

The process of exocytosis by which chylomicrons are secreted from intestinal cells into the chyle (lymph) and then enter the bloodstream through the thoracic duct.