What are lipids

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What are lipids?   :

What are lipids? Lipids are inorganic compounds that are poorly soluble in water. They are the main energy source of the body, they have regulatory functions, they play a major role in homeostasis and they form the phospholipid bilayer .

There are three basic sources of fatty acids in animals that can be used for energy conversion processes: :

There are three basic sources of fatty acids in animals that can be used for energy conversion processes:

So what happens when we eat food high in lipids or fatty acids? :

So what happens when we eat food high in lipids or fatty acids?

MOUTH:

MOUTH Dietary triglycerides enter; cholesteryl esters, triacylglycerols and phospholipids remain unchanged.

STOMACH:

STOMACH Digestion of lipids begin here. Lingual and gastric lipase enzymes degrade triacylglycerol molecules. These “acid lipases” play a particularly important role in lipid digestion in neonates, for whom milk fat is the primary source of calories . They are also important digestive enzymes in individuals with pancreatic insufficiency. The stomach has cholesteryl esters, phospholipids , triacylglycerols and some short and medium chain fatty acids.

SMALL INTESTINE:

SMALL INTESTINE Emulsification and degradation of dietary lipids occur here. Fats enter the stomach as insoluble macroscopic particles and must be emulsified by bile acids such as glycocholate which are secreted by the bile duct and function as detergents to promote the formation of finely dispersed microscopic micelles which can then be absorbed through the intestinal wall. Bile salts are made in the liver from cholesterol and stored in the gallbladder .

PowerPoint Presentation:

Formation of lipids into micelles orient the ester bonds of the lipid toward the surface of the micelle, rendering the bonds more susceptible to digestion by pancreatic lipases that are in aqueous solution. These emulsifying agents interact with the dietary lipid particles and the aqueous duodenal contents, thereby stabilizing the particles as they become smaller, and preventing them from coalescing. Emulsification of dietary lipids occur in the duodenum. Micelle

The pancreatic secretion of hydrolytic enzymes which degrade dietary lipids is hormonally controlled by the following process: :

The pancreatic secretion of hydrolytic enzymes which degrade dietary lipids is hormonally controlled by the following process: The presence of partially digested protein in the upper regions of the small intestine are detected by the cells of mucosa of these regions and cholecystokinin (CKK) is produced. This acts on the gallbladder and exocrine cells. Bile and digestive enzymes are released. Gastric motility decreases resulting in the slower release of the gastric contents into the small intestine. The low pH of gastric contents ( chyme ) entering the small intestine stimulates other cells to produce secretin . This stimulates the pancreas and liver to release a watery solution rich in bicarbonate which helps to neutralize the pH of the intestinal contents to optimum pH for the process to occur.

REACTIONS OCCURING IN THE SMALL INTESTINE:

REACTIONS OCCURING IN THE SMALL INTESTINE

PowerPoint Presentation:

Products of digestion in the jejunum ; free fatty acids free cholesterol 2-monoaclyglycerol together with bile salts and soluble vitamins form micelles. These are disc-shaped clusters of amphipathic lipids that coalesce with their hydrophobic groups on the inside and their hydrophilic groups on the inside. They are soluble in aqueous environment of intestinal lumen. These micelles move to the brush border membrane of enterocytes which is the primary site of lipid absorption. Cholesterol is poorly absorbed by enterocytes . Short and medium chain fatty acids do not require assistance of micelles for absorption by the enterocytes .

RESYNTHESIS OF TAG AND CHOLESTEROL ESTERS:

RESYNTHESIS OF TAG AND CHOLESTEROL ESTERS The mixture of lipids absorbed by intestinal mucosa moves towards the endoplasmic reticulum where biosynthesis of complex lipids takes place.

FATES OF CHYLOMICRON COMPONENTS:

FATES OF CHYLOMICRON COMPONENTS Triglycerol - This is broken down in capillaries of skeletal muscles, adipose tissue, liver, lung, heart and kidney.

PowerPoint Presentation:

Cholesteryl esters, phospholipids, apolipoproteins , fat soluble vitamins, and some TAG bind to receptors on liver and are endocytosed . The remnants are hydrolysed to component parts. This is a receptor mediated process. Cholesterols can be recycled by the body.

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